NBME Lab Values: Official USMLE Reference Ranges

Every reference range from the official USMLE Laboratory Values table, the same table you can open on screen during the exam. Search by test name or filter by panel. Units are shown exactly as the official table lists them: conventional units and SI units.

88 tests · Official usmle.org table · Last checked 24 October 2026

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AllElectrolytes and general chemistryHepaticOther serumLipidsIron studiesEndocrineImmunoglobulinsArterial blood gasesCerebrospinal fluidComplete blood countCoagulationOther hematologicUrineBody mass index

Test	Reference range	SI reference interval
Serum › Electrolytes and general chemistry
Sodium (Na+)	136-146 mEq/L	136-146 mmol/L
Potassium (K+)	3.5-5.0 mEq/L	3.5-5.0 mmol/L
Chloride (Cl−)	95-105 mEq/L	95-105 mmol/L
Bicarbonate (HCO3−)	22-28 mEq/L	22-28 mmol/L
Urea nitrogen	7-18 mg/dL	2.5-6.4 mmol/L
Creatinine	0.6-1.2 mg/dL	53-106 μmol/L
Glucose	Fasting: 70-100 mg/dL Random, non-fasting: <140 mg/dL	3.8-5.6 mmol/L <7.77 mmol/L
Calcium	8.4-10.2 mg/dL	2.1-2.6 mmol/L
Magnesium (Mg2+)	1.5-2.0 mg/dL	0.75-1.0 mmol/L
Phosphorus (inorganic)	3.0-4.5 mg/dL	1.0-1.5 mmol/L
Serum › Hepatic
Alanine aminotransferase (ALT)	10-40 U/L	10-40 U/L
Aspartate aminotransferase (AST)	12-38 U/L	12-38 U/L
Alkaline phosphatase	25-100 U/L	25-100 U/L
Bilirubin, total // direct	0.1-1.0 mg/dL // 0.0-0.3 mg/dL	2-17 μmol/L // 0-5 μmol/L
Proteins, total	6.0-7.8 g/dL	60-78 g/L
Albumin	3.5-5.5 g/dL	35-55 g/L
Globulin	2.3-3.5 g/dL	23-35 g/L
Serum › Other serum
Amylase	25-125 U/L	25-125 U/L
Lipase	13-60 U/L	13-60 U/L
Creatinine clearance	Male: 97-137 mL/min Female: 88-128 mL/min	97-137 mL/min 88-128 mL/min
Creatine kinase	Male: 25-90 U/L Female: 10-70 U/L	25-90 U/L 10-70 U/L
Lactate dehydrogenase	45-200 U/L	45-200 U/L
Osmolality	275-295 mOsmol/kg H2O	275-295 mOsmol/kg H2O
Troponin I	≤0.04 ng/mL	≤0.04 µg/L
Uric acid	3.0-8.2 mg/dL	0.18-0.48 mmol/L
Serum › Lipids
Cholesterol, total	Normal: <200 mg/dL High: >240 mg/dL	<5.2 mmol/L >6.2 mmol/L
Cholesterol, HDL	40-60 mg/dL	1.0-1.6 mmol/L
Cholesterol, LDL	<160 mg/dL	<4.2 mmol/L
Triglycerides	Normal: <150 mg/dL Borderline: 151-199 mg/dL	<1.70 mmol/L 1.71-2.25 mmol/L
Serum › Iron studies
Ferritin	Male: 20-250 ng/mL Female: 10-120 ng/mL	20-250 μg/L 10-120 μg/L
Iron	Male: 65-175 µg/dL Female: 50-170 μg/dL	11.6-31.3 μmol/L 9.0-30.4 μmol/L
Total iron-binding capacity	250-400 µg/dL	44.8-71.6 μmol/L
Transferrin	200-360 mg/dL	2.0-3.6 g/L
Serum › Endocrine
Follicle-stimulating hormone	Male: 4-25 mIU/mL Female: premenopause 4-30 mIU/mL midcycle peak 10-90 mIU/mL postmenopause 40-250 mIU/mL	4-25 IU/L 4-30 IU/L 10-90 IU/L 40-250 IU/L
Luteinizing hormone	Male: 6-23 mIU/mL Female: follicular phase 5-30 mIU/mL midcycle 75-150 mIU/mL postmenopause 30-200 mIU/mL	6-23 IU/L 5-30 IU/L 75-150 IU/L 30-200 IU/L
Growth hormone, arginine stimulation	Fasting: <5 ng/mL Provocative stimuli: >7 ng/mL	<5 μg/L >7 μg/L
Prolactin (hPRL)	Male: <17 ng/mL Female: <25 ng/mL	<17 μg/L <25 μg/L
Cortisol	0800 h: 5-23 μg/dL 1600 h: 3-15 μg/dL 2000 h: <50% of 0800 h	138-635 nmol/L 82-413 nmol/L Fraction of 0800 h: <0.50
TSH	0.4-4.0 μU/mL	0.4-4.0 mIU/L
Triiodothyronine (T3) (RIA)	100-200 ng/dL	1.5-3.1 nmol/L
Triiodothyronine (T3) resin uptake	25%-35%	0.25-0.35
Thyroxine (T4)	5-12 μg/dL	64-155 nmol/L
Free T4	0.9-1.7 ng/dL	12.0-21.9 pmol/L
Thyroidal iodine (123I) uptake	8%-30% of administered dose/24 h	0.08-0.30/24 h
Intact PTH	10-60 pg/mL	10-60 ng/L
17-Hydroxycorticosteroids	Male: 3.0-10.0 mg/24 h Female: 2.0-8.0 mg/24 h	8.2-27.6 μmol/24 h 5.5-22.0 μmol/24 h
17-Ketosteroids, total	Male: 8-20 mg/24 h Female: 6-15 mg/24 h	28-70 μmol/24 h 21-52 μmol/24 h
Serum › Immunoglobulins
IgA	76-390 mg/dL	0.76-3.90 g/L
IgE	0-380 IU/mL	0-380 kIU/L
IgG	650-1500 mg/dL	6.5-15.0 g/L
IgM	50-300 mg/dL	0.5-3.0 g/L
Arterial blood gases (room air) › Arterial blood gases
Po2	75-105 mm Hg	10.0-14.0 kPa
Pco2	33-45 mm Hg	4.4-5.9 kPa
pH	7.35-7.45	[H+] 36-44 nmol/L
Cerebrospinal fluid
Cell count	0-5/mm3	0-5 × 106/L
Chloride	118-132 mEq/L	118-132 mmol/L
Gamma globulin	3%-12% total proteins	0.03-0.12
Glucose	40-70 mg/dL	2.2-3.9 mmol/L
Pressure	70-180 mm H2O	70-180 mm H2O
Proteins, total	<40 mg/dL	<0.40 g/L
Hematologic › Complete blood count
Hematocrit	Male: 41%-53% Female: 36%-46%	0.41-0.53 0.36-0.46
Hemoglobin, blood	Male: 13.5-17.5 g/dL Female: 12.0-16.0 g/dL	135-175 g/L 120-160 g/L
Mean corpuscular hemoglobin (MCH)	25-35 pg/cell	0.39-0.54 fmol/cell
Mean corpuscular hemoglobin conc. (MCHC)	31%-36% Hb/cell	4.8-5.6 mmol Hb/L
Mean corpuscular volume (MCV)	80-100 μm3	80-100 fL
Volume, plasma	Male: 25-43 mL/kg Female: 28-45 mL/kg	0.025-0.043 L/kg 0.028-0.045 L/kg
Volume, red cell	Male: 20-36 mL/kg Female: 19-31 mL/kg	0.020-0.036 L/kg 0.019-0.031 L/kg
Leukocyte count (WBC)	4500-11,000/mm3	4.5-11.0 × 109/L
Neutrophils, segmented	54%-62%	0.54-0.62
Neutrophils, bands	3%-5%	0.03-0.05
Lymphocytes	25%-33%	0.25-0.33
Monocytes	3%-7%	0.03-0.07
Eosinophils	1%-3%	0.01-0.03
Basophils	0%-0.75%	0.00-0.0075
Platelet count	150,000-400,000/mm3	150-400 × 109/L
Hematologic › Coagulation
Partial thromboplastin time (PTT/aPTT) (activated)	25-40 seconds	25-40 seconds
Prothrombin time (PT)	11-15 seconds	11-15 seconds
D-dimer	≤250 ng/mL	≤1.4 nmol/L
Hematologic › Other hematologic
Reticulocyte count	0.5%-1.5%	0.005-0.015
Erythrocyte count (RBC)	Male: 4.3-5.9 million/mm3 Female: 3.5-5.5 million/mm3	4.3-5.9 × 1012/L 3.5-5.5 × 1012/L
Erythrocyte sedimentation rate (Westergren)	Male: 0-15 mm/h Female: 0-20 mm/h	0-15 mm/h 0-20 mm/h
CD4+ T-lymphocyte count	≥500/mm3	≥0.5 × 109/L
Hemoglobin A1c	≤6%	≤42 mmol/mol
Urine
Calcium	100-300 mg/24 h	2.5-7.5 mmol/24 h
Osmolality	50-1200 mOsmol/kg H2O	50-1200 mOsmol/kg H2O
Oxalate	8-40 μg/mL	90-445 μmol/L
Proteins, total	<150 mg/24 h	<0.15 g/24 h
Body mass index
Body mass index (BMI)	Adult: 19-25 kg/m2	not listed

For exam study, not for clinical use.

Source: USMLE Step 1 Sample Test Questions: USMLE Laboratory Values, pages 7 to 9 (USMLE program, usmle.org) ^[1]; NBME Laboratory Values (NBME, nbme.org) ^[2]

Grouping follows the official table: Serum (electrolytes and general chemistry, hepatic, other, lipids, iron studies, endocrine, immunoglobulins), arterial blood gases, cerebrospinal fluid, hematologic, urine and body mass index. Hemoglobin A1c is listed under Hematologic, Endocrine in the official table and appears under Other hematologic here.

How to use this table

• Search matches the test name and common short forms (for example BUN, TSH, ALT, PT, MCV, CD4).
• Filter by panel to see one block of the official table, such as Electrolytes, Hepatic or Complete blood count.
• Units: the first column is the official “Reference Range” (conventional units such as mg/dL and mEq/L); the second is the official “SI Reference Intervals” column (such as mmol/L).
• Sex and timing: some tests list separate male and female ranges, and cortisol lists times of day, exactly as in the official table.

Values are copied from the official PDF and checked automatically against its text. Ranges are written with a hyphen (136-146) where the PDF uses a dash.

Worked example

FAQ

Sources

Every formula, cutoff and reference value on this page comes from the official sources below. Click any source to check it yourself.

1. USMLE Step 1 Sample Test Questions: USMLE Laboratory Values, pages 7 to 9 (PDF updated 2 April 2026, retrieved 24 October 2026) (USMLE program, usmle.org)
2. NBME Laboratory Values (page updated 17 June 2026, retrieved 24 October 2026) (NBME, nbme.org)
3. NBME Laboratory Reference Values (PDF) (NBME, nbme.org)

Last checked: 24 October 2026. Spotted a mistake? Please tell us on the Corrections page.

For exam study, not for clinical use. This tool is for learning how the formulas work. It is not medical advice. See the Medical disclaimer.