Normal Lab Values

Typical adult reference ranges for blood, urine and cerebrospinal fluid tests, in conventional and SI units, with the source of every value. Search it, or print it.

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Normal Lab Values

Typical adult reference ranges. Read every result against the range printed on its own report. From biofidex.com/tools/normal-lab-values, reviewed 17 October 2026.

Typical adult ranges, not your lab's. Each lab sets its own range for its method and population, and children and pregnancy have different ones. Read a result against the range printed on its report. Rows marked Guideline are decision limits from the named guideline, not reference ranges.

Blood count

Red cells, white cells and platelets (CBC, FBC).

Test	Conventional	SI
HemoglobinHb, haemoglobin The oxygen-carrying protein in red cells; low in anaemia. Source: USMLE	Men13.5–17.5g/dL Women12.0–16.0g/dL	Men135–175g/L Women120–160g/L
HematocritHct, packed cell volume The share of the blood's volume taken up by red cells. Source: USMLE	Men41–53% Women36–46%	Men0.41–0.53L/L Women0.36–0.46L/L
Red cell countRBC, erythrocytes The number of red cells in a volume of blood. Source: USMLE	Men4.3–5.9× 10⁶/µL Women3.5–5.5× 10⁶/µL	Men4.3–5.9× 10¹²/L Women3.5–5.5× 10¹²/L
Mean corpuscular volumeMCV The average size of a red cell: small in iron deficiency, large in B12 or folate deficiency. Source: USMLE	80–100fL	80–100fL
Mean corpuscular hemoglobinMCH The average amount of hemoglobin in one red cell. Source: USMLE	25–35pg	25–35pg
Mean corpuscular hemoglobin concentrationMCHC How concentrated the hemoglobin is inside red cells; low when they are pale (hypochromic). The USMLE prints it as 31–36% Hb per cell, the same figure. Source: USMLE; SI converted here at × 10	31–36g/dL	310–360g/L
Red cell distribution widthRDW How much red cells vary in size; wide when two populations are mixed, as in early iron deficiency. Source: ABIM	9.0–14.5%	9.0–14.5%
White cell countWBC, leukocytes All white cells together: high in infection and inflammation, low when the marrow is suppressed. Source: USMLE	4,500–11,000/µL	4.5–11.0× 10⁹/L
Neutrophils The commonest white cell, first to respond to bacterial infection. Source: USMLE	Segmented54–62% of white cells Bands3–5% of white cells	Segmented0.54–0.62fraction Bands0.03–0.05fraction
Absolute neutrophil countANC Neutrophils counted as cells rather than a share; the figure that decides infection risk. Source: ABIM; SI converted here at × 0.001	2,000–8,250/µL	2–8.25× 10⁹/L
Lymphocytes B, T and natural killer cells: the white cells of adaptive immunity. Source: USMLE	25–33% of white cells	0.25–0.33fraction
Absolute lymphocyte count Lymphocytes counted as cells rather than a share of the white count. Source: ABIM; SI converted here at × 0.001	1,200–4,950/µL	1.2–4.95× 10⁹/L
Monocytes White cells that become macrophages in the tissues. Source: USMLE	3–7% of white cells	0.03–0.07fraction
Eosinophils White cells raised in allergy and parasitic infection. Source: USMLE	1–3% of white cells	0.01–0.03fraction
Basophils The rarest white cell, which releases histamine. Source: USMLE	0–0.75% of white cells	0–0.0075fraction
Platelet countPLT Cell fragments that start a clot; low counts mean bleeding risk. Source: USMLE	150,000–400,000/µL	150–400× 10⁹/L
Reticulocyte count Young red cells: shows whether the marrow is answering an anaemia. Source: USMLE	0.5–1.5% of red cells	0.005–0.015fraction
Erythrocyte sedimentation rateESR, Westergren How far red cells settle in an hour; rises with inflammation, age and anaemia. Source: USMLE	Men0–15mm/h Women0–20mm/h	Men0–15mm/h Women0–20mm/h

HemoglobinHb, haemoglobin
The oxygen-carrying protein in red cells; low in anaemia.
Source: USMLE
Conventional
- Men13.5–17.5g/dL
- Women12.0–16.0g/dL
SI
- Men135–175g/L
- Women120–160g/L
HematocritHct, packed cell volume
The share of the blood's volume taken up by red cells.
Source: USMLE
Conventional
- Men41–53%
- Women36–46%
SI
- Men0.41–0.53L/L
- Women0.36–0.46L/L
Red cell countRBC, erythrocytes
The number of red cells in a volume of blood.
Source: USMLE
Conventional
- Men4.3–5.9× 10⁶/µL
- Women3.5–5.5× 10⁶/µL
SI
- Men4.3–5.9× 10¹²/L
- Women3.5–5.5× 10¹²/L
Mean corpuscular volumeMCV
The average size of a red cell: small in iron deficiency, large in B12 or folate deficiency.
Source: USMLE
Conventional
- 80–100fL
SI
- 80–100fL
Mean corpuscular hemoglobinMCH
The average amount of hemoglobin in one red cell.
Source: USMLE
Conventional
- 25–35pg
SI
- 25–35pg
Mean corpuscular hemoglobin concentrationMCHC
How concentrated the hemoglobin is inside red cells; low when they are pale (hypochromic).
The USMLE prints it as 31–36% Hb per cell, the same figure.
Source: USMLE; SI converted here at × 10
Conventional
- 31–36g/dL
SI
- 310–360g/L
Red cell distribution widthRDW
How much red cells vary in size; wide when two populations are mixed, as in early iron deficiency.
Source: ABIM
Conventional
- 9.0–14.5%
SI
- 9.0–14.5%
White cell countWBC, leukocytes
All white cells together: high in infection and inflammation, low when the marrow is suppressed.
Source: USMLE
Conventional
- 4,500–11,000/µL
SI
- 4.5–11.0× 10⁹/L
Neutrophils
The commonest white cell, first to respond to bacterial infection.
Source: USMLE
Conventional
- Segmented54–62% of white cells
- Bands3–5% of white cells
SI
- Segmented0.54–0.62fraction
- Bands0.03–0.05fraction
Absolute neutrophil countANC
Neutrophils counted as cells rather than a share; the figure that decides infection risk.
Source: ABIM; SI converted here at × 0.001
Conventional
- 2,000–8,250/µL
SI
- 2–8.25× 10⁹/L
Lymphocytes
B, T and natural killer cells: the white cells of adaptive immunity.
Source: USMLE
Conventional
- 25–33% of white cells
SI
- 0.25–0.33fraction
Absolute lymphocyte count
Lymphocytes counted as cells rather than a share of the white count.
Source: ABIM; SI converted here at × 0.001
Conventional
- 1,200–4,950/µL
SI
- 1.2–4.95× 10⁹/L
Monocytes
White cells that become macrophages in the tissues.
Source: USMLE
Conventional
- 3–7% of white cells
SI
- 0.03–0.07fraction
Eosinophils
White cells raised in allergy and parasitic infection.
Source: USMLE
Conventional
- 1–3% of white cells
SI
- 0.01–0.03fraction
Basophils
The rarest white cell, which releases histamine.
Source: USMLE
Conventional
- 0–0.75% of white cells
SI
- 0–0.0075fraction
Platelet countPLT
Cell fragments that start a clot; low counts mean bleeding risk.
Source: USMLE
Conventional
- 150,000–400,000/µL
SI
- 150–400× 10⁹/L
Reticulocyte count
Young red cells: shows whether the marrow is answering an anaemia.
Source: USMLE
Conventional
- 0.5–1.5% of red cells
SI
- 0.005–0.015fraction
Erythrocyte sedimentation rateESR, Westergren
How far red cells settle in an hour; rises with inflammation, age and anaemia.
Source: USMLE
Conventional
- Men0–15mm/h
- Women0–20mm/h
SI
- Men0–15mm/h
- Women0–20mm/h

Clotting

How fast blood clots, and what it clots with.

Test	Conventional	SI
Prothrombin timePT Tests the extrinsic and common pathways; long with warfarin, vitamin K lack or liver disease. Source: USMLE	11–15seconds	11–15seconds
Activated partial thromboplastin timeaPTT, PTT Tests the intrinsic and common pathways; long with heparin or haemophilia. Source: USMLE	25–40seconds	25–40seconds
Fibrinogen The protein that becomes fibrin, the mesh of a clot. Source: ABIM; SI converted here at × 0.01	200–400mg/dL	2–4g/L
D-dimer A breakdown product of fibrin; a normal result helps rule out a clot. Labs report it in two kinds of unit (D-dimer units, or fibrinogen-equivalent units about twice as large), so the cut-off depends on the assay. ABIM gives < 0.5 µg/mL. Source: USMLE	≤ 250ng/mL	≤ 1.4nmol/L

Prothrombin timePT
Tests the extrinsic and common pathways; long with warfarin, vitamin K lack or liver disease.
Source: USMLE
Conventional
- 11–15seconds
SI
- 11–15seconds
Activated partial thromboplastin timeaPTT, PTT
Tests the intrinsic and common pathways; long with heparin or haemophilia.
Source: USMLE
Conventional
- 25–40seconds
SI
- 25–40seconds
Fibrinogen
The protein that becomes fibrin, the mesh of a clot.
Source: ABIM; SI converted here at × 0.01
Conventional
- 200–400mg/dL
SI
- 2–4g/L
D-dimer
A breakdown product of fibrin; a normal result helps rule out a clot.
Labs report it in two kinds of unit (D-dimer units, or fibrinogen-equivalent units about twice as large), so the cut-off depends on the assay. ABIM gives < 0.5 µg/mL.
Source: USMLE
Conventional
- ≤ 250ng/mL
SI
- ≤ 1.4nmol/L

Electrolytes and minerals

The salts and minerals that keep water, nerves and muscle in balance.

Test	Conventional	SI
SodiumNa⁺ The main cation outside cells; it tracks water balance more than salt intake. Source: USMLE	136–146mEq/L	136–146mmol/L
PotassiumK⁺ The main cation inside cells; small changes affect the heart's rhythm. Source: USMLE	3.5–5.0mEq/L	3.5–5.0mmol/L
ChlorideCl⁻ The main anion outside cells; follows sodium and moves against bicarbonate. Source: USMLE	95–105mEq/L	95–105mmol/L
BicarbonateHCO₃⁻, total CO₂ The blood's main buffer base; low in metabolic acidosis, high in metabolic alkalosis. Source: USMLE	22–28mEq/L	22–28mmol/L
Anion gap Sodium minus chloride and bicarbonate: the anions a routine panel doesn't measure. Source: ABIM	7–13mEq/L	7–13mmol/L
Calcium, totalCa Bound and free calcium together; read it with albumin, which carries much of it. Source: USMLE	8.4–10.2mg/dL	2.1–2.6mmol/L
Calcium, ionized The free calcium that acts on nerves and muscle, unaffected by albumin. Source: ABIM	1.16–1.31mmol/L	1.16–1.31mmol/L
MagnesiumMg²⁺ A cofactor for hundreds of enzymes; low magnesium keeps potassium and calcium low too. From ABIM: the USMLE's mg/dL and mmol/L figures for magnesium don't agree with each other. Source: ABIM; SI converted here at × 0.4114	1.6–2.6mg/dL	0.658–1.07mmol/L
Phosphatephosphorus, inorganic Part of bone, ATP and DNA; regulated with calcium by PTH and vitamin D. Source: USMLE	3.0–4.5mg/dL	1.0–1.5mmol/L
Osmolality, serum All dissolved particles together, mostly sodium, glucose and urea. Source: USMLE	275–295mOsm/kg H₂O	275–295mmol/kg

SodiumNa⁺
The main cation outside cells; it tracks water balance more than salt intake.
Source: USMLE
Conventional
- 136–146mEq/L
SI
- 136–146mmol/L
PotassiumK⁺
The main cation inside cells; small changes affect the heart's rhythm.
Source: USMLE
Conventional
- 3.5–5.0mEq/L
SI
- 3.5–5.0mmol/L
ChlorideCl⁻
The main anion outside cells; follows sodium and moves against bicarbonate.
Source: USMLE
Conventional
- 95–105mEq/L
SI
- 95–105mmol/L
BicarbonateHCO₃⁻, total CO₂
The blood's main buffer base; low in metabolic acidosis, high in metabolic alkalosis.
Source: USMLE
Conventional
- 22–28mEq/L
SI
- 22–28mmol/L
Anion gap
Sodium minus chloride and bicarbonate: the anions a routine panel doesn't measure.
Source: ABIM
Conventional
- 7–13mEq/L
SI
- 7–13mmol/L
Calcium, totalCa
Bound and free calcium together; read it with albumin, which carries much of it.
Source: USMLE
Conventional
- 8.4–10.2mg/dL
SI
- 2.1–2.6mmol/L
Calcium, ionized
The free calcium that acts on nerves and muscle, unaffected by albumin.
Source: ABIM
Conventional
- 1.16–1.31mmol/L
SI
- 1.16–1.31mmol/L
MagnesiumMg²⁺
A cofactor for hundreds of enzymes; low magnesium keeps potassium and calcium low too.
From ABIM: the USMLE's mg/dL and mmol/L figures for magnesium don't agree with each other.
Source: ABIM; SI converted here at × 0.4114
Conventional
- 1.6–2.6mg/dL
SI
- 0.658–1.07mmol/L
Phosphatephosphorus, inorganic
Part of bone, ATP and DNA; regulated with calcium by PTH and vitamin D.
Source: USMLE
Conventional
- 3.0–4.5mg/dL
SI
- 1.0–1.5mmol/L
Osmolality, serum
All dissolved particles together, mostly sodium, glucose and urea.
Source: USMLE
Conventional
- 275–295mOsm/kg H₂O
SI
- 275–295mmol/kg

Kidney function

The wastes the kidneys clear, and how well they clear them.

Test	Conventional	SI
Blood urea nitrogenBUN, urea nitrogen The nitrogen in urea, the liver's way of disposing of protein; rises when the kidneys clear less. Source: USMLE	7–18mg/dL	2.5–6.4mmol/L urea
Urea The whole urea molecule, as many labs outside the US report it. The USMLE's BUN range written as urea: urea in mg/dL is BUN × 2.14. Source: USMLE	15–39mg/dL	2.5–6.4mmol/L
Creatinine A waste product of muscle, cleared by the kidneys at a steady rate; the basis of eGFR. Source: USMLE	0.6–1.2mg/dL	53–106µmol/L
Estimated GFReGFRGuideline Kidney filtration estimated from creatinine, age and sex, graded G1 to G5. G1 or G2 is chronic kidney disease only with another marker of kidney damage, such as albumin in the urine. Source: KDIGO	G1, normal or high≥ 90mL/min/1.73 m² G2, mildly decreased60–89mL/min/1.73 m² G3a, mildly to moderately decreased45–59mL/min/1.73 m² G3b, moderately to severely decreased30–44mL/min/1.73 m² G4, severely decreased15–29mL/min/1.73 m² G5, kidney failure< 15mL/min/1.73 m²	G1, normal or high≥ 90mL/min/1.73 m² G2, mildly decreased60–89mL/min/1.73 m² G3a, mildly to moderately decreased45–59mL/min/1.73 m² G3b, moderately to severely decreased30–44mL/min/1.73 m² G4, severely decreased15–29mL/min/1.73 m² G5, kidney failure< 15mL/min/1.73 m²
Uric acidurate The end product of purine breakdown; crystals of it cause gout. Source: USMLE	3.0–8.2mg/dL	0.18–0.48mmol/L
Creatinine clearance Filtration measured from a timed urine collection and a blood creatinine. Source: USMLE	Men97–137mL/min Women88–128mL/min	Men97–137mL/min Women88–128mL/min

Blood urea nitrogenBUN, urea nitrogen
The nitrogen in urea, the liver's way of disposing of protein; rises when the kidneys clear less.
Source: USMLE
Conventional
- 7–18mg/dL
SI
- 2.5–6.4mmol/L urea
Urea
The whole urea molecule, as many labs outside the US report it.
The USMLE's BUN range written as urea: urea in mg/dL is BUN × 2.14.
Source: USMLE
Conventional
- 15–39mg/dL
SI
- 2.5–6.4mmol/L
Creatinine
A waste product of muscle, cleared by the kidneys at a steady rate; the basis of eGFR.
Source: USMLE
Conventional
- 0.6–1.2mg/dL
SI
- 53–106µmol/L
Estimated GFReGFRGuideline
Kidney filtration estimated from creatinine, age and sex, graded G1 to G5.
G1 or G2 is chronic kidney disease only with another marker of kidney damage, such as albumin in the urine.
Source: KDIGO
Conventional
- G1, normal or high≥ 90mL/min/1.73 m²
- G2, mildly decreased60–89mL/min/1.73 m²
- G3a, mildly to moderately decreased45–59mL/min/1.73 m²
- G3b, moderately to severely decreased30–44mL/min/1.73 m²
- G4, severely decreased15–29mL/min/1.73 m²
- G5, kidney failure< 15mL/min/1.73 m²
SI
- G1, normal or high≥ 90mL/min/1.73 m²
- G2, mildly decreased60–89mL/min/1.73 m²
- G3a, mildly to moderately decreased45–59mL/min/1.73 m²
- G3b, moderately to severely decreased30–44mL/min/1.73 m²
- G4, severely decreased15–29mL/min/1.73 m²
- G5, kidney failure< 15mL/min/1.73 m²
Uric acidurate
The end product of purine breakdown; crystals of it cause gout.
Source: USMLE
Conventional
- 3.0–8.2mg/dL
SI
- 0.18–0.48mmol/L
Creatinine clearance
Filtration measured from a timed urine collection and a blood creatinine.
Source: USMLE
Conventional
- Men97–137mL/min
- Women88–128mL/min
SI
- Men97–137mL/min
- Women88–128mL/min

Liver function

Liver enzymes, bilirubin and the proteins the liver makes.

Test	Conventional	SI
Alanine aminotransferaseALT, SGPT An enzyme found mainly in liver cells; it leaks out when they are damaged. Source: USMLE	10–40U/L	10–40U/L
Aspartate aminotransferaseAST, SGOT An enzyme in liver, heart and muscle; higher than ALT points to alcohol or a source outside the liver. Source: USMLE	12–38U/L	12–38U/L
Alkaline phosphataseALP An enzyme of the bile ducts and bone; high when bile flow is blocked or bone is growing. Source: USMLE	25–100U/L	25–100U/L
Gamma-glutamyl transferaseGGT A bile duct enzyme; confirms that a high ALP comes from the liver, and rises with alcohol. Source: ABIM	Men9–50U/L Women8–40U/L	Men9–50U/L Women8–40U/L
Bilirubin, total The yellow breakdown product of hemoglobin; above about 2.5 mg/dL it shows as jaundice. Source: USMLE	0.1–1.0mg/dL	2–17µmol/L
Bilirubin, directconjugated Bilirubin the liver has conjugated; high when bile cannot drain. Source: USMLE	0–0.3mg/dL	0–5µmol/L
Albumin The main protein the liver makes; low in liver disease, malnutrition and protein loss. Source: USMLE	3.5–5.5g/dL	35–55g/L
Protein, total Albumin and globulins together. Source: USMLE	6.0–7.8g/dL	60–78g/L
Globulin Total protein minus albumin: mostly antibodies and carrier proteins. Source: USMLE	2.3–3.5g/dL	23–35g/L
Lactate dehydrogenaseLDH An enzyme in nearly every cell; rises with tissue damage and hemolysis. Ranges vary widely with the method; ABIM gives 80–225 U/L. Source: USMLE	45–200U/L	45–200U/L

Alanine aminotransferaseALT, SGPT
An enzyme found mainly in liver cells; it leaks out when they are damaged.
Source: USMLE
Conventional
- 10–40U/L
SI
- 10–40U/L
Aspartate aminotransferaseAST, SGOT
An enzyme in liver, heart and muscle; higher than ALT points to alcohol or a source outside the liver.
Source: USMLE
Conventional
- 12–38U/L
SI
- 12–38U/L
Alkaline phosphataseALP
An enzyme of the bile ducts and bone; high when bile flow is blocked or bone is growing.
Source: USMLE
Conventional
- 25–100U/L
SI
- 25–100U/L
Gamma-glutamyl transferaseGGT
A bile duct enzyme; confirms that a high ALP comes from the liver, and rises with alcohol.
Source: ABIM
Conventional
- Men9–50U/L
- Women8–40U/L
SI
- Men9–50U/L
- Women8–40U/L
Bilirubin, total
The yellow breakdown product of hemoglobin; above about 2.5 mg/dL it shows as jaundice.
Source: USMLE
Conventional
- 0.1–1.0mg/dL
SI
- 2–17µmol/L
Bilirubin, directconjugated
Bilirubin the liver has conjugated; high when bile cannot drain.
Source: USMLE
Conventional
- 0–0.3mg/dL
SI
- 0–5µmol/L
Albumin
The main protein the liver makes; low in liver disease, malnutrition and protein loss.
Source: USMLE
Conventional
- 3.5–5.5g/dL
SI
- 35–55g/L
Protein, total
Albumin and globulins together.
Source: USMLE
Conventional
- 6.0–7.8g/dL
SI
- 60–78g/L
Globulin
Total protein minus albumin: mostly antibodies and carrier proteins.
Source: USMLE
Conventional
- 2.3–3.5g/dL
SI
- 23–35g/L
Lactate dehydrogenaseLDH
An enzyme in nearly every cell; rises with tissue damage and hemolysis.
Ranges vary widely with the method; ABIM gives 80–225 U/L.
Source: USMLE
Conventional
- 45–200U/L
SI
- 45–200U/L

Glucose and diabetes

Blood sugar now, and averaged over the last two to three months.

Test	Conventional	SI
Glucoseblood sugar Sugar in the plasma, the body's main fuel. Source: USMLE	Fasting70–100mg/dL Random< 140mg/dL	Fasting3.8–5.6mmol/L Random< 7.77mmol/L
Fasting plasma glucose, for diagnosisGuideline Glucose after at least eight hours without food, judged against the diagnostic cut-offs. The WHO sets impaired fasting glucose at 110–125 mg/dL (6.1–6.9 mmol/L) rather than 100–125. Without clear symptoms, diabetes needs two abnormal results. Source: ADA 2026, WHO	Normal< 100mg/dL Prediabetes100–125mg/dL Diabetes≥ 126mg/dL	Normal< 5.6mmol/L Prediabetes5.6–6.9mmol/L Diabetes≥ 7.0mmol/L
2-hour glucose, 75 g OGTToral glucose tolerance testGuideline Glucose two hours after drinking 75 g of glucose. Source: ADA 2026	Normal< 140mg/dL Prediabetes140–199mg/dL Diabetes≥ 200mg/dL	Normal< 7.8mmol/L Prediabetes7.8–11.0mmol/L Diabetes≥ 11.1mmol/L
Random glucose, with symptomsGuideline Glucose at any time of day in someone with thirst, frequent urination and weight loss, or in a hyperglycaemic crisis. Source: ADA 2026	Diabetes≥ 200mg/dL	Diabetes≥ 11.1mmol/L
Hemoglobin A1cHbA1c, glycated hemoglobinGuideline The share of hemoglobin carrying glucose: average blood sugar over the last two to three months. The USMLE table gives ≤ 6% (≤ 42 mmol/mol) as normal. Source: ADA 2026	Normal< 5.7% Prediabetes5.7–6.4% Diabetes≥ 6.5%	Normal< 39mmol/mol Prediabetes39–47mmol/mol Diabetes≥ 48mmol/mol

Glucoseblood sugar
Sugar in the plasma, the body's main fuel.
Source: USMLE
Conventional
- Fasting70–100mg/dL
- Random< 140mg/dL
SI
- Fasting3.8–5.6mmol/L
- Random< 7.77mmol/L
Fasting plasma glucose, for diagnosisGuideline
Glucose after at least eight hours without food, judged against the diagnostic cut-offs.
The WHO sets impaired fasting glucose at 110–125 mg/dL (6.1–6.9 mmol/L) rather than 100–125. Without clear symptoms, diabetes needs two abnormal results.
Source: ADA 2026, WHO
Conventional
- Normal< 100mg/dL
- Prediabetes100–125mg/dL
- Diabetes≥ 126mg/dL
SI
- Normal< 5.6mmol/L
- Prediabetes5.6–6.9mmol/L
- Diabetes≥ 7.0mmol/L
2-hour glucose, 75 g OGTToral glucose tolerance testGuideline
Glucose two hours after drinking 75 g of glucose.
Source: ADA 2026
Conventional
- Normal< 140mg/dL
- Prediabetes140–199mg/dL
- Diabetes≥ 200mg/dL
SI
- Normal< 7.8mmol/L
- Prediabetes7.8–11.0mmol/L
- Diabetes≥ 11.1mmol/L
Random glucose, with symptomsGuideline
Glucose at any time of day in someone with thirst, frequent urination and weight loss, or in a hyperglycaemic crisis.
Source: ADA 2026
Conventional
- Diabetes≥ 200mg/dL
SI
- Diabetes≥ 11.1mmol/L
Hemoglobin A1cHbA1c, glycated hemoglobinGuideline
The share of hemoglobin carrying glucose: average blood sugar over the last two to three months.
The USMLE table gives ≤ 6% (≤ 42 mmol/mol) as normal.
Source: ADA 2026
Conventional
- Normal< 5.7%
- Prediabetes5.7–6.4%
- Diabetes≥ 6.5%
SI
- Normal< 39mmol/mol
- Prediabetes39–47mmol/mol
- Diabetes≥ 48mmol/mol

Lipids

Cholesterol and triglycerides, judged against cardiovascular risk.

Test	Conventional	SI
Cholesterol, totalGuideline All the cholesterol carried in the blood's lipoproteins. ATP III's bands from 2001, still printed on many reports. Current guidelines judge risk by LDL and non-HDL cholesterol instead. Source: ATP III	Desirable< 200mg/dL Borderline high200–239mg/dL High≥ 240mg/dL	Desirable< 5.2mmol/L Borderline high5.2–6.2mmol/L High≥ 6.2mmol/L
LDL cholesterolLDL-CGuideline Cholesterol carried in low-density lipoprotein, the kind that builds up in arteries. Goals set by each person's risk; very high risk means established heart or artery disease with other risks. Older reports print ATP III's bands: optimal < 100, borderline high 130–159, high 160–189 mg/dL. Source: ACC/AHA 2026	Goal, most adults< 100mg/dL Goal, high risk< 70mg/dL Goal, very high risk< 55mg/dL Severe hypercholesterolaemia≥ 190mg/dL	Goal, most adults< 2.6mmol/L Goal, high risk< 1.8mmol/L Goal, very high risk< 1.4mmol/L Severe hypercholesterolaemia≥ 4.9mmol/L
Non-HDL cholesterolGuideline Total cholesterol minus HDL: all the cholesterol in particles that can build up in arteries. Source: ACC/AHA 2026	Goal, most adults< 130mg/dL Goal, high risk< 100mg/dL Goal, very high risk< 85mg/dL	Goal, most adults< 3.4mmol/L Goal, high risk< 2.6mmol/L Goal, very high risk< 2.2mmol/L
HDL cholesterolHDL-CGuideline Cholesterol carried back to the liver in high-density lipoprotein; higher is better. ATP III's bands from 2001. Source: ATP III	Low< 40mg/dL High≥ 60mg/dL	Low< 1.0mmol/L High≥ 1.6mmol/L
TriglyceridesTGGuideline Fats carried mostly in VLDL; measured fasting, since a meal raises them. ATP III's bands from 2001. The 2026 ACC/AHA guideline groups fasting triglycerides as 150–499, 500–999 and ≥ 1000 mg/dL. Source: ATP III	Normal< 150mg/dL Borderline high150–199mg/dL High200–499mg/dL Very high≥ 500mg/dL	Normal< 1.7mmol/L Borderline high1.7–2.2mmol/L High2.3–5.6mmol/L Very high≥ 5.6mmol/L

Cholesterol, totalGuideline
All the cholesterol carried in the blood's lipoproteins.
ATP III's bands from 2001, still printed on many reports. Current guidelines judge risk by LDL and non-HDL cholesterol instead.
Source: ATP III
Conventional
- Desirable< 200mg/dL
- Borderline high200–239mg/dL
- High≥ 240mg/dL
SI
- Desirable< 5.2mmol/L
- Borderline high5.2–6.2mmol/L
- High≥ 6.2mmol/L
LDL cholesterolLDL-CGuideline
Cholesterol carried in low-density lipoprotein, the kind that builds up in arteries.
Goals set by each person's risk; very high risk means established heart or artery disease with other risks. Older reports print ATP III's bands: optimal < 100, borderline high 130–159, high 160–189 mg/dL.
Source: ACC/AHA 2026
Conventional
- Goal, most adults< 100mg/dL
- Goal, high risk< 70mg/dL
- Goal, very high risk< 55mg/dL
- Severe hypercholesterolaemia≥ 190mg/dL
SI
- Goal, most adults< 2.6mmol/L
- Goal, high risk< 1.8mmol/L
- Goal, very high risk< 1.4mmol/L
- Severe hypercholesterolaemia≥ 4.9mmol/L
Non-HDL cholesterolGuideline
Total cholesterol minus HDL: all the cholesterol in particles that can build up in arteries.
Source: ACC/AHA 2026
Conventional
- Goal, most adults< 130mg/dL
- Goal, high risk< 100mg/dL
- Goal, very high risk< 85mg/dL
SI
- Goal, most adults< 3.4mmol/L
- Goal, high risk< 2.6mmol/L
- Goal, very high risk< 2.2mmol/L
HDL cholesterolHDL-CGuideline
Cholesterol carried back to the liver in high-density lipoprotein; higher is better.
ATP III's bands from 2001.
Source: ATP III
Conventional
- Low< 40mg/dL
- High≥ 60mg/dL
SI
- Low< 1.0mmol/L
- High≥ 1.6mmol/L
TriglyceridesTGGuideline
Fats carried mostly in VLDL; measured fasting, since a meal raises them.
ATP III's bands from 2001. The 2026 ACC/AHA guideline groups fasting triglycerides as 150–499, 500–999 and ≥ 1000 mg/dL.
Source: ATP III
Conventional
- Normal< 150mg/dL
- Borderline high150–199mg/dL
- High200–499mg/dL
- Very high≥ 500mg/dL
SI
- Normal< 1.7mmol/L
- Borderline high1.7–2.2mmol/L
- High2.3–5.6mmol/L
- Very high≥ 5.6mmol/L

Thyroid

The pituitary's signal to the thyroid, and the hormones it makes.

Test	Conventional	SI
Thyroid-stimulating hormoneTSH The pituitary's signal to the thyroid: high when the thyroid is underactive, low when overactive. Source: USMLE	0.4–4.0µIU/mL	0.4–4.0mIU/L
Free thyroxinefree T4 The unbound thyroxine that can enter cells. Source: USMLE	0.9–1.7ng/dL	12.0–21.9pmol/L
Free triiodothyroninefree T3 The unbound form of the active thyroid hormone. Source: ABIM; SI converted here at × 1.536	2.3–4.2pg/mL	3.53–6.45pmol/L
Thyroxine, totalT4 Bound and free thyroxine together; changes with the proteins that carry it. Source: USMLE	5–12µg/dL	64–155nmol/L
Triiodothyronine, totalT3 Bound and free T3 together. Source: USMLE	100–200ng/dL	1.5–3.1nmol/L

Thyroid-stimulating hormoneTSH
The pituitary's signal to the thyroid: high when the thyroid is underactive, low when overactive.
Source: USMLE
Conventional
- 0.4–4.0µIU/mL
SI
- 0.4–4.0mIU/L
Free thyroxinefree T4
The unbound thyroxine that can enter cells.
Source: USMLE
Conventional
- 0.9–1.7ng/dL
SI
- 12.0–21.9pmol/L
Free triiodothyroninefree T3
The unbound form of the active thyroid hormone.
Source: ABIM; SI converted here at × 1.536
Conventional
- 2.3–4.2pg/mL
SI
- 3.53–6.45pmol/L
Thyroxine, totalT4
Bound and free thyroxine together; changes with the proteins that carry it.
Source: USMLE
Conventional
- 5–12µg/dL
SI
- 64–155nmol/L
Triiodothyronine, totalT3
Bound and free T3 together.
Source: USMLE
Conventional
- 100–200ng/dL
SI
- 1.5–3.1nmol/L

Iron studies

Iron in the blood, what carries it, and what is stored.

Test	Conventional	SI
Iron, serum Iron carried in the blood on transferrin; it varies through the day. Source: USMLE	Men65–175µg/dL Women50–170µg/dL	Men11.6–31.3µmol/L Women9.0–30.4µmol/L
Total iron-binding capacityTIBC How much iron transferrin could carry; high in iron deficiency. Source: USMLE	250–400µg/dL	44.8–71.6µmol/L
Transferrin saturation Serum iron as a share of TIBC: low in iron deficiency, high in iron overload. Source: ABIM	20–50%	20–50%
Ferritin The iron-storage protein; low ferritin is the surest sign of iron deficiency, but inflammation raises it. Source: USMLE	Men20–250ng/mL Women10–120ng/mL	Men20–250µg/L Women10–120µg/L
Transferrin The protein that carries iron in the blood. Source: USMLE	200–360mg/dL	2.0–3.6g/L

Iron, serum
Iron carried in the blood on transferrin; it varies through the day.
Source: USMLE
Conventional
- Men65–175µg/dL
- Women50–170µg/dL
SI
- Men11.6–31.3µmol/L
- Women9.0–30.4µmol/L
Total iron-binding capacityTIBC
How much iron transferrin could carry; high in iron deficiency.
Source: USMLE
Conventional
- 250–400µg/dL
SI
- 44.8–71.6µmol/L
Transferrin saturation
Serum iron as a share of TIBC: low in iron deficiency, high in iron overload.
Source: ABIM
Conventional
- 20–50%
SI
- 20–50%
Ferritin
The iron-storage protein; low ferritin is the surest sign of iron deficiency, but inflammation raises it.
Source: USMLE
Conventional
- Men20–250ng/mL
- Women10–120ng/mL
SI
- Men20–250µg/L
- Women10–120µg/L
Transferrin
The protein that carries iron in the blood.
Source: USMLE
Conventional
- 200–360mg/dL
SI
- 2.0–3.6g/L

Heart

Signs of heart muscle damage and of a heart under strain.

Test	Conventional	SI
Troponin IcTnI A protein of heart muscle; any rise means heart muscle damage. The limit is each assay's own 99th percentile, so it differs between assays (Fifth Universal Definition of MI, 2026). Source: USMLE, 5th UDMI	≤ 0.04ng/mL	≤ 0.04µg/L
High-sensitivity troponin Ihs-cTnI Troponin I measured down to small amounts, with sex-specific limits. Each assay has its own sex-specific 99th-percentile limit; these are typical. Source: ABIM, 5th UDMI	Men≤ 20ng/L Women≤ 15ng/L	Men≤ 20ng/L Women≤ 15ng/L
High-sensitivity troponin Ths-cTnT Troponin T measured down to small amounts, with sex-specific limits. Each assay has its own sex-specific 99th-percentile limit; these are typical. Source: ABIM, 5th UDMI	Men≤ 15ng/L Women≤ 10ng/L	Men≤ 15ng/L Women≤ 10ng/L
Creatine kinase, totalCK, CPK An enzyme of skeletal and heart muscle; very high after muscle injury. From ABIM: the USMLE table's older CK range (men 25–90 U/L) is well below what current labs use. Source: ABIM	Men55–170U/L Women30–135U/L	Men55–170U/L Women30–135U/L
CK-MB The form of creatine kinase richest in heart muscle; largely replaced by troponin. Source: ABIM	< 5% of total CK	< 5% of total CK
B-type natriuretic peptideBNPGuideline A hormone released by stretched heart muscle; a low value makes heart failure unlikely. Source: ABIM, ESC 2026	Heart failure unlikely, sudden symptoms< 100pg/mL Heart failure unlikely, outpatient< 35pg/mL	Heart failure unlikely, sudden symptoms< 100ng/L Heart failure unlikely, outpatient< 35ng/L
NT-proBNPGuideline The inactive fragment released with BNP; its cut-offs for heart failure rise with age. The sudden-symptom cut-offs assume eGFR above 60; below it, ≥ 1200 pg/mL makes heart failure likely. Source: ABIM, ESC 2026	Heart failure unlikely, sudden symptoms≤ 300pg/mL Likely, sudden symptoms, age 18–49≥ 450pg/mL Likely, sudden symptoms, age 50–75≥ 900pg/mL Likely, sudden symptoms, over 75≥ 1,800pg/mL Heart failure unlikely, outpatient< 125pg/mL	Heart failure unlikely, sudden symptoms≤ 300ng/L Likely, sudden symptoms, age 18–49≥ 450ng/L Likely, sudden symptoms, age 50–75≥ 900ng/L Likely, sudden symptoms, over 75≥ 1,800ng/L Heart failure unlikely, outpatient< 125ng/L

Troponin IcTnI
A protein of heart muscle; any rise means heart muscle damage.
The limit is each assay's own 99th percentile, so it differs between assays (Fifth Universal Definition of MI, 2026).
Source: USMLE, 5th UDMI
Conventional
- ≤ 0.04ng/mL
SI
- ≤ 0.04µg/L
High-sensitivity troponin Ihs-cTnI
Troponin I measured down to small amounts, with sex-specific limits.
Each assay has its own sex-specific 99th-percentile limit; these are typical.
Source: ABIM, 5th UDMI
Conventional
- Men≤ 20ng/L
- Women≤ 15ng/L
SI
- Men≤ 20ng/L
- Women≤ 15ng/L
High-sensitivity troponin Ths-cTnT
Troponin T measured down to small amounts, with sex-specific limits.
Each assay has its own sex-specific 99th-percentile limit; these are typical.
Source: ABIM, 5th UDMI
Conventional
- Men≤ 15ng/L
- Women≤ 10ng/L
SI
- Men≤ 15ng/L
- Women≤ 10ng/L
Creatine kinase, totalCK, CPK
An enzyme of skeletal and heart muscle; very high after muscle injury.
From ABIM: the USMLE table's older CK range (men 25–90 U/L) is well below what current labs use.
Source: ABIM
Conventional
- Men55–170U/L
- Women30–135U/L
SI
- Men55–170U/L
- Women30–135U/L
CK-MB
The form of creatine kinase richest in heart muscle; largely replaced by troponin.
Source: ABIM
Conventional
- < 5% of total CK
SI
- < 5% of total CK
B-type natriuretic peptideBNPGuideline
A hormone released by stretched heart muscle; a low value makes heart failure unlikely.
Source: ABIM, ESC 2026
Conventional
- Heart failure unlikely, sudden symptoms< 100pg/mL
- Heart failure unlikely, outpatient< 35pg/mL
SI
- Heart failure unlikely, sudden symptoms< 100ng/L
- Heart failure unlikely, outpatient< 35ng/L
NT-proBNPGuideline
The inactive fragment released with BNP; its cut-offs for heart failure rise with age.
The sudden-symptom cut-offs assume eGFR above 60; below it, ≥ 1200 pg/mL makes heart failure likely.
Source: ABIM, ESC 2026
Conventional
- Heart failure unlikely, sudden symptoms≤ 300pg/mL
- Likely, sudden symptoms, age 18–49≥ 450pg/mL
- Likely, sudden symptoms, age 50–75≥ 900pg/mL
- Likely, sudden symptoms, over 75≥ 1,800pg/mL
- Heart failure unlikely, outpatient< 125pg/mL
SI
- Heart failure unlikely, sudden symptoms≤ 300ng/L
- Likely, sudden symptoms, age 18–49≥ 450ng/L
- Likely, sudden symptoms, age 50–75≥ 900ng/L
- Likely, sudden symptoms, over 75≥ 1,800ng/L
- Heart failure unlikely, outpatient< 125ng/L

Inflammation

Signs that inflammation is present somewhere in the body.

Test	Conventional	SI
C-reactive proteinCRP A protein the liver makes within hours of infection or inflammation. Many labs report CRP in mg/L, where this limit is 8. Source: ABIM; SI converted here at × 10	≤ 0.8mg/dL	≤ 8mg/L
High-sensitivity CRPhs-CRPGuideline CRP measured at low levels, used to grade cardiovascular risk. Measured twice, about two weeks apart, and averaged. Above 10 mg/L, look for an infection or inflammation and test again. Source: AHA/CDC	Low risk< 1.0mg/L Average risk1.0–3.0mg/L High risk> 3.0mg/L	Low risk< 1.0mg/L Average risk1.0–3.0mg/L High risk> 3.0mg/L

C-reactive proteinCRP
A protein the liver makes within hours of infection or inflammation.
Many labs report CRP in mg/L, where this limit is 8.
Source: ABIM; SI converted here at × 10
Conventional
- ≤ 0.8mg/dL
SI
- ≤ 8mg/L
High-sensitivity CRPhs-CRPGuideline
CRP measured at low levels, used to grade cardiovascular risk.
Measured twice, about two weeks apart, and averaged. Above 10 mg/L, look for an infection or inflammation and test again.
Source: AHA/CDC
Conventional
- Low risk< 1.0mg/L
- Average risk1.0–3.0mg/L
- High risk> 3.0mg/L
SI
- Low risk< 1.0mg/L
- Average risk1.0–3.0mg/L
- High risk> 3.0mg/L

Vitamins

Vitamins whose lack causes anaemia, nerve damage or weak bones.

Test	Conventional	SI
Vitamin B12cobalamin Needed to make DNA in dividing cells and to keep nerves healthy. Source: ABIM; SI converted here at × 0.7378	200–800pg/mL	148–590pmol/L
Folate, serumfolic acid A B vitamin needed to make DNA; deficiency gives large red cells, as B12 deficiency does. Source: ABIM; SI converted here at × 2.266	1.8–9.0ng/mL	4.08–20.4nmol/L
25-hydroxyvitamin Dvitamin D, 25(OH)DGuideline The stored form of vitamin D, the one measured to judge someone's supply. Cut-offs for bone health. The Endocrine Society stopped endorsing a 30 ng/mL target in 2024; ABIM's list still gives 30–60 ng/mL. Source: NAM	At risk of deficiency< 12ng/mL Not enough for some12–20ng/mL Enough for nearly everyone≥ 20ng/mL Possibly too high> 50ng/mL	At risk of deficiency< 30nmol/L Not enough for some30–50nmol/L Enough for nearly everyone≥ 50nmol/L Possibly too high> 125nmol/L

Vitamin B12cobalamin
Needed to make DNA in dividing cells and to keep nerves healthy.
Source: ABIM; SI converted here at × 0.7378
Conventional
- 200–800pg/mL
SI
- 148–590pmol/L
Folate, serumfolic acid
A B vitamin needed to make DNA; deficiency gives large red cells, as B12 deficiency does.
Source: ABIM; SI converted here at × 2.266
Conventional
- 1.8–9.0ng/mL
SI
- 4.08–20.4nmol/L
25-hydroxyvitamin Dvitamin D, 25(OH)DGuideline
The stored form of vitamin D, the one measured to judge someone's supply.
Cut-offs for bone health. The Endocrine Society stopped endorsing a 30 ng/mL target in 2024; ABIM's list still gives 30–60 ng/mL.
Source: NAM
Conventional
- At risk of deficiency< 12ng/mL
- Not enough for some12–20ng/mL
- Enough for nearly everyone≥ 20ng/mL
- Possibly too high> 50ng/mL
SI
- At risk of deficiency< 30nmol/L
- Not enough for some30–50nmol/L
- Enough for nearly everyone≥ 50nmol/L
- Possibly too high> 125nmol/L

Other chemistry

Pancreatic enzymes, lactate, ammonia, cortisol and PTH.

Test	Conventional	SI
Amylase A starch-digesting enzyme from the pancreas and salivary glands. Source: USMLE	25–125U/L	25–125U/L
Lipase A fat-digesting enzyme from the pancreas; more specific than amylase for pancreatitis. Ranges vary widely with the method; ABIM gives 10–140 U/L. Source: USMLE	13–60U/L	13–60U/L
Lactatelactic acid Made when cells lack oxygen; high in shock and sepsis. Source: ABIM	6–19mg/dL	0.7–2.1mmol/L
Ammonia A toxic product of protein breakdown that the liver turns into urea. Converted as ammonia (NH₃). A lab that reports ammonia nitrogen multiplies by 0.714 instead, so check its unit. Source: ABIM; SI converted here at × 0.5872	40–70µg/dL	23.5–41.1µmol/L
Cortisol, 8 AM The adrenal stress hormone, highest in the morning. Source: USMLE	5–23µg/dL	138–635nmol/L
Parathyroid hormone, intactPTH Raises blood calcium by acting on bone, kidney and, through vitamin D, the gut. Source: USMLE	10–60pg/mL	10–60ng/L

Amylase
A starch-digesting enzyme from the pancreas and salivary glands.
Source: USMLE
Conventional
- 25–125U/L
SI
- 25–125U/L
Lipase
A fat-digesting enzyme from the pancreas; more specific than amylase for pancreatitis.
Ranges vary widely with the method; ABIM gives 10–140 U/L.
Source: USMLE
Conventional
- 13–60U/L
SI
- 13–60U/L
Lactatelactic acid
Made when cells lack oxygen; high in shock and sepsis.
Source: ABIM
Conventional
- 6–19mg/dL
SI
- 0.7–2.1mmol/L
Ammonia
A toxic product of protein breakdown that the liver turns into urea.
Converted as ammonia (NH₃). A lab that reports ammonia nitrogen multiplies by 0.714 instead, so check its unit.
Source: ABIM; SI converted here at × 0.5872
Conventional
- 40–70µg/dL
SI
- 23.5–41.1µmol/L
Cortisol, 8 AM
The adrenal stress hormone, highest in the morning.
Source: USMLE
Conventional
- 5–23µg/dL
SI
- 138–635nmol/L
Parathyroid hormone, intactPTH
Raises blood calcium by acting on bone, kidney and, through vitamin D, the gut.
Source: USMLE
Conventional
- 10–60pg/mL
SI
- 10–60ng/L

Arterial blood gases

Acid–base balance and oxygen, in arterial blood on room air.

Test	Conventional	SI
pH Acidity of arterial blood: below the range is acidaemia, above it alkalaemia. As hydrogen ion: 36–44 nmol/L. Source: USMLE	7.35–7.45	7.35–7.45
PaCO₂ Carbon dioxide in arterial blood, set by breathing: the respiratory side of acid–base. Source: USMLE	33–45mm Hg	4.4–5.9kPa
PaO₂ Oxygen dissolved in arterial blood; falls with age and lung disease. Source: USMLE	75–105mm Hg	10.0–14.0kPa
Bicarbonate, arterialHCO₃⁻ Calculated from pH and PaCO₂: the metabolic side of acid–base. Source: ABIM	23–26mEq/L	23–26mmol/L
Oxygen saturationSaO₂ The share of hemoglobin carrying oxygen. Source: ABIM	≥ 95%	≥ 95%

pH
Acidity of arterial blood: below the range is acidaemia, above it alkalaemia.
As hydrogen ion: 36–44 nmol/L.
Source: USMLE
Conventional
- 7.35–7.45
SI
- 7.35–7.45
PaCO₂
Carbon dioxide in arterial blood, set by breathing: the respiratory side of acid–base.
Source: USMLE
Conventional
- 33–45mm Hg
SI
- 4.4–5.9kPa
PaO₂
Oxygen dissolved in arterial blood; falls with age and lung disease.
Source: USMLE
Conventional
- 75–105mm Hg
SI
- 10.0–14.0kPa
Bicarbonate, arterialHCO₃⁻
Calculated from pH and PaCO₂: the metabolic side of acid–base.
Source: ABIM
Conventional
- 23–26mEq/L
SI
- 23–26mmol/L
Oxygen saturationSaO₂
The share of hemoglobin carrying oxygen.
Source: ABIM
Conventional
- ≥ 95%
SI
- ≥ 95%

Urine

Urinalysis and timed collections.

Test	Conventional	SI
pH, urine Acidity of urine, which shifts with diet and acid–base balance. Usually 5.0–6.0 (MSD Manual). Source: ABIM, MSD Manual	4.5–8.0	4.5–8.0
Specific gravitySG How concentrated urine is compared with water. Source: ABIM	1.002–1.030	1.002–1.030
Osmolality, urine Dissolved particles in urine; shows how well the kidneys concentrate or dilute it. Source: USMLE	50–1,200mOsm/kg H₂O	50–1,200mmol/kg
Protein, 24-hour Protein lost in a day's urine; more suggests kidney disease. Source: USMLE	< 150mg/24 h	< 0.15g/24 h
Albumin-to-creatinine ratioACR, uACRGuideline Albumin in a spot urine, corrected for how concentrated it is; the earliest sign of kidney damage. Source: KDIGO	A1, normal to mildly increased< 30mg/g A2, moderately increased30–300mg/g A3, severely increased> 300mg/g	A1, normal to mildly increased< 3mg/mmol A2, moderately increased3–30mg/mmol A3, severely increased> 30mg/mmol
Glucose, urine Appears when blood glucose passes the kidney's threshold, about 180 mg/dL. A dipstick detects about 50 mg/dL; any amount is abnormal. Source: MSD Manual	Negative	Negative
Ketones Made when the body burns fat for fuel: in fasting and uncontrolled diabetes. Source: OHSU	Negative	Negative
Blood, dipstick Detects hemoglobin, from red cells or free; myoglobin also reacts. Source: OHSU	Negative	Negative
Nitrite Made from nitrate by many urinary bacteria; positive means bacteria are present. Source: MSD Manual	Negative	Negative
Leukocyte esterase An enzyme of white cells; positive means pyuria, often from infection. Source: OHSU	Negative	Negative
Red cells, microscopy Red cells seen per high-power field of spun urine. Up to 5/HPF can be normal, for example after exercise. Source: MSD Manual	< 3/HPF	< 3/HPF
White cells, microscopy White cells seen per high-power field of spun urine. Source: MSD Manual	< 5/HPF	< 5/HPF
Hyaline casts Protein moulds of the tubules; a few are normal, and cellular casts are not. Source: OHSU	0–2/LPF	0–2/LPF
Calcium, 24-hour Calcium lost in a day's urine; high levels favour kidney stones. Source: USMLE	100–300mg/24 h	2.5–7.5mmol/24 h

pH, urine
Acidity of urine, which shifts with diet and acid–base balance.
Usually 5.0–6.0 (MSD Manual).
Source: ABIM, MSD Manual
Conventional
- 4.5–8.0
SI
- 4.5–8.0
Specific gravitySG
How concentrated urine is compared with water.
Source: ABIM
Conventional
- 1.002–1.030
SI
- 1.002–1.030
Osmolality, urine
Dissolved particles in urine; shows how well the kidneys concentrate or dilute it.
Source: USMLE
Conventional
- 50–1,200mOsm/kg H₂O
SI
- 50–1,200mmol/kg
Protein, 24-hour
Protein lost in a day's urine; more suggests kidney disease.
Source: USMLE
Conventional
- < 150mg/24 h
SI
- < 0.15g/24 h
Albumin-to-creatinine ratioACR, uACRGuideline
Albumin in a spot urine, corrected for how concentrated it is; the earliest sign of kidney damage.
Source: KDIGO
Conventional
- A1, normal to mildly increased< 30mg/g
- A2, moderately increased30–300mg/g
- A3, severely increased> 300mg/g
SI
- A1, normal to mildly increased< 3mg/mmol
- A2, moderately increased3–30mg/mmol
- A3, severely increased> 30mg/mmol
Glucose, urine
Appears when blood glucose passes the kidney's threshold, about 180 mg/dL.
A dipstick detects about 50 mg/dL; any amount is abnormal.
Source: MSD Manual
Conventional
- Negative
SI
- Negative
Ketones
Made when the body burns fat for fuel: in fasting and uncontrolled diabetes.
Source: OHSU
Conventional
- Negative
SI
- Negative
Blood, dipstick
Detects hemoglobin, from red cells or free; myoglobin also reacts.
Source: OHSU
Conventional
- Negative
SI
- Negative
Nitrite
Made from nitrate by many urinary bacteria; positive means bacteria are present.
Source: MSD Manual
Conventional
- Negative
SI
- Negative
Leukocyte esterase
An enzyme of white cells; positive means pyuria, often from infection.
Source: OHSU
Conventional
- Negative
SI
- Negative
Red cells, microscopy
Red cells seen per high-power field of spun urine.
Up to 5/HPF can be normal, for example after exercise.
Source: MSD Manual
Conventional
- < 3/HPF
SI
- < 3/HPF
White cells, microscopy
White cells seen per high-power field of spun urine.
Source: MSD Manual
Conventional
- < 5/HPF
SI
- < 5/HPF
Hyaline casts
Protein moulds of the tubules; a few are normal, and cellular casts are not.
Source: OHSU
Conventional
- 0–2/LPF
SI
- 0–2/LPF
Calcium, 24-hour
Calcium lost in a day's urine; high levels favour kidney stones.
Source: USMLE
Conventional
- 100–300mg/24 h
SI
- 2.5–7.5mmol/24 h

Cerebrospinal fluid

The fluid around the brain and spinal cord, from a lumbar puncture.

Test	Conventional	SI
Appearance Normal fluid looks like water; 300 or more cells per µL make it cloudy. Source: MSD Manual	Clear, colourless	Clear, colourless
Opening pressure Pressure measured lying on the side, as the needle enters the spinal canal. Source: USMLE	70–180mm H₂O	70–180mm H₂O
White cells Normally a few lymphocytes; neutrophils point to bacterial meningitis. Source: USMLE	0–5/µL	0–5× 10⁶/L
Red cells None normally; blood comes from a traumatic tap or a bleed. Source: ABIM	0	0
Glucose About 60% of the blood glucose; low in bacterial, fungal and TB meningitis. Compare it with a blood glucose taken at the same time: the CSF-to-blood ratio is normally about 0.6. Source: USMLE, MSD Manual	40–70mg/dL	2.2–3.9mmol/L
Protein, total Raised by infection, bleeding, a blocked spinal canal and Guillain–Barré syndrome. Source: USMLE	< 40mg/dL	< 0.40g/L
Chloride Higher in CSF than in blood. Source: USMLE	118–132mEq/L	118–132mmol/L
Gamma globulin Antibodies as a share of CSF protein; raised in multiple sclerosis and infection. Source: USMLE	3–12% of total protein	0.03–0.12fraction

Appearance
Normal fluid looks like water; 300 or more cells per µL make it cloudy.
Source: MSD Manual
Conventional
- Clear, colourless
SI
- Clear, colourless
Opening pressure
Pressure measured lying on the side, as the needle enters the spinal canal.
Source: USMLE
Conventional
- 70–180mm H₂O
SI
- 70–180mm H₂O
White cells
Normally a few lymphocytes; neutrophils point to bacterial meningitis.
Source: USMLE
Conventional
- 0–5/µL
SI
- 0–5× 10⁶/L
Red cells
None normally; blood comes from a traumatic tap or a bleed.
Source: ABIM
Conventional
- 0
SI
- 0
Glucose
About 60% of the blood glucose; low in bacterial, fungal and TB meningitis.
Compare it with a blood glucose taken at the same time: the CSF-to-blood ratio is normally about 0.6.
Source: USMLE, MSD Manual
Conventional
- 40–70mg/dL
SI
- 2.2–3.9mmol/L
Protein, total
Raised by infection, bleeding, a blocked spinal canal and Guillain–Barré syndrome.
Source: USMLE
Conventional
- < 40mg/dL
SI
- < 0.40g/L
Chloride
Higher in CSF than in blood.
Source: USMLE
Conventional
- 118–132mEq/L
SI
- 118–132mmol/L
Gamma globulin
Antibodies as a share of CSF protein; raised in multiple sclerosis and infection.
Source: USMLE
Conventional
- 3–12% of total protein
SI
- 0.03–0.12fraction

Questions

Reading a reference range

What does a normal range mean?

A reference range is usually the middle 95% of results from a group of healthy people. By design, about 1 healthy person in 20 has a result just outside it on any one test, so a value slightly out of range is not by itself a sign of disease.

Why does my lab report show a different range?

Each lab sets its range for its own instrument, method and population, and some ranges change with age, sex or pregnancy. A result is judged against the range printed beside it on its own report, not against a table like this one.

What is the difference between conventional and SI units?

Conventional units give the mass of a substance in a volume, such as mg/dL. SI units give the amount in moles, such as mmol/L. Labs in the United States report most tests in conventional units; most other countries use SI. The mg/dL to mmol/L converter changes one into the other.

Why are some rows guideline cut-offs instead of ranges?

For glucose, HbA1c, cholesterol and a few other tests, what matters is the risk a value carries, so guidelines set cut-offs from studies of outcomes rather than from the spread of healthy people. Those rows are marked Guideline and name the guideline.

Are these the same as the USMLE lab values?

Most rows here are the USMLE's own values, and each row names its source. Other references differ a little: the ABIM list gives sodium as 136–145 mmol/L where the USMLE gives 136–146. In an exam, use the values the exam gives you.

Sources

Where the values come from

Every row names its source. Most reference ranges are from the table of laboratory values printed in USMLE and NBME exams, and ABIM's list fills its gaps; where a source prints conventional units only, the row says the SI figure was converted here. Cut-offs marked Guideline are from the guideline named. Checked against these sources on 17 October 2026.