NBME Lab Values: Reference Ranges and Value Interpreter
NBME lab values are handed to you on screen during the exam, so what is tested is interpretation, not recall. All 105 of them sit here in 14 searchable panels, with an interpreter that reads any number you type against its reference range.
Not affiliated with, endorsed by, or sponsored by the NBME® or USMLE®. Reference intervals are provided for study and are not medical advice.
Interpret a result against the official sheet
Pick a test, type the number from your vignette, and read it against the NBME lab values reference interval: normal, low or high, with the diagnoses each direction points to.
Choose a lab test above to see its reference range and interpret a value.
NBME lab values chart: all 105 reference ranges
Every row of the NBME lab values sheet. Search by test, filter by panel, send one to the interpreter, or export the whole set as CSV.
Showing 105 of 105 reference values.
| Test | Reference range | Yield | |
|---|---|---|---|
| Electrolytes & Renal | |||
| Sodium (Na⁺) | 136–146 mEq/L | High-yield | |
| Potassium (K⁺) | 3.5–5 mEq/L | High-yield | |
| Chloride (Cl⁻) | 95–105 mEq/L | Medium | |
| Bicarbonate (HCO₃⁻) | 22–28 mEq/L | High-yield | |
| Urea Nitrogen (BUN) | 7–18 mg/dL | High-yield | |
| Creatinine | 0.6–1.2 mg/dL | High-yield | |
| Glucose (Fasting) | 70–100 mg/dL | High-yield | |
| Calcium | 8.4–10.2 mg/dL | High-yield | |
| Magnesium (Mg²⁺) | 1.5–2 mg/dL | Medium | |
| Phosphorus | 3–4.5 mg/dL | Lower-yield | |
| Uric Acid | 3–8.2 mg/dL | Medium | |
| Osmolality (Serum) | 275–295 mOsm/kg | High-yield | |
| Hepatic Panel | |||
| ALT | 10–40 U/L | High-yield | |
| AST | 12–38 U/L | High-yield | |
| Alkaline Phosphatase | 25–100 U/L | High-yield | |
| Bilirubin, Total | 0.1–1 mg/dL | High-yield | |
| Bilirubin, Direct | 0–0.3 mg/dL | Medium | |
| Proteins, Total | 6–7.8 g/dL | Lower-yield | |
| Albumin | 3.5–5.5 g/dL | High-yield | |
| Globulin | 2.3–3.5 g/dL | Lower-yield | |
| Lipid Panel | |||
| Cholesterol, Total | <200 mg/dL (normal) | Medium | |
| HDL Cholesterol | 40–60 mg/dL | Lower-yield | |
| LDL Cholesterol | <160 mg/dL | Medium | |
| Triglycerides | <150 mg/dL (normal) | Lower-yield | |
| Iron Studies | |||
| Ferritin(Male) | 20–250 ng/mL | High-yield | |
| Ferritin(Female) | 10–120 ng/mL | High-yield | |
| Serum Iron(Male) | 65–175 µg/dL | Medium | |
| Serum Iron(Female) | 50–170 µg/dL | Medium | |
| Total Iron-Binding Capacity (TIBC) | 250–400 µg/dL | Medium | |
| Transferrin | 200–360 mg/dL | Medium | |
| Endocrine | |||
| TSH | 0.4–4 µU/mL | High-yield | |
| Free T4 | 0.9–1.7 ng/dL | High-yield | |
| Thyroxine (T4), Total | 5–12 µg/dL | Lower-yield | |
| Triiodothyronine (T3) | 100–200 ng/dL | Lower-yield | |
| Intact PTH | 10–60 pg/mL | High-yield | |
| Cortisol (AM, 0800h) | 5–23 µg/dL | Medium | |
| Hemoglobin A1c | ≤6% | High-yield | |
| FSH(Male) | 4–25 mIU/mL | Medium | |
| FSH(Female, Premenopause) | 4–30 mIU/mL | Medium | |
| FSH(Female, Postmenopause) | 40–250 mIU/mL | Lower-yield | |
| LH(Male) | 6–23 mIU/mL | Medium | |
| LH(Female, Follicular) | 5–30 mIU/mL | Medium | |
| Prolactin(Male) | <17 ng/mL | Medium | |
| Prolactin(Female) | <25 ng/mL | Medium | |
| Growth Hormone (GH)(Fasting) | Fasting <5 ng/mL; Stimulated >7 ng/mL | Lower-yield | |
| T3 Resin Uptake | 25–35 % | Lower-yield | |
| Thyroidal Iodine (¹²³I) Uptake(24h) | 8%–30% of dose at 24h | Lower-yield | |
| 17-Hydroxycorticosteroids(Male, 24h urine) | 3–10 mg/24h | Lower-yield | |
| 17-Hydroxycorticosteroids(Female, 24h urine) | 2–8 mg/24h | Lower-yield | |
| 17-Ketosteroids(Male, 24h urine) | 8–20 mg/24h | Lower-yield | |
| 17-Ketosteroids(Female, 24h urine) | 6–15 mg/24h | Lower-yield | |
| Arterial Blood Gas | |||
| pH (Arterial) | 7.35–7.45 | High-yield | |
| PaCO₂ | 33–45 mmHg | High-yield | |
| PaO₂ | 75–105 mmHg | High-yield | |
| Hematology (CBC) | |||
| Hematocrit(Male) | 41–53 % | Medium | |
| Hematocrit(Female) | 36–46 % | Medium | |
| Hemoglobin(Male) | 13.5–17.5 g/dL | High-yield | |
| Hemoglobin(Female) | 12–16 g/dL | High-yield | |
| MCV | 80–100 µm³ | High-yield | |
| MCH | 25–35 pg/cell | Lower-yield | |
| MCHC | 31–36 % Hb/cell | Lower-yield | |
| Leukocyte Count (WBC) | 4500–11000 /mm³ | High-yield | |
| Platelet Count | 150000–400000 /mm³ | High-yield | |
| Reticulocyte Count | 0.5–1.5 % | Medium | |
| Erythrocyte Count (RBC)(Male) | 4.3–5.9 million/mm³ | Lower-yield | |
| Erythrocyte Count (RBC)(Female) | 3.5–5.5 million/mm³ | Lower-yield | |
| ESR (Westergren)(Male) | 0–15 mm/h | Medium | |
| ESR (Westergren)(Female) | 0–20 mm/h | Medium | |
| CD4+ T-Lymphocyte Count | ≥500/mm³ | High-yield | |
| Coagulation | |||
| Prothrombin Time (PT) | 11–15 seconds | High-yield | |
| PTT / aPTT | 25–40 seconds | High-yield | |
| D-Dimer | ≤250 ng/mL | Medium | |
| Cerebrospinal Fluid | |||
| CSF Glucose | 40–70 mg/dL | High-yield | |
| CSF Protein, Total | <40 mg/dL | High-yield | |
| CSF Cell Count | 0–5 /mm³ | High-yield | |
| CSF Pressure (Opening) | 70–180 mm H₂O | Medium | |
| CSF Chloride | 118–132 mEq/L | Lower-yield | |
| CSF Gamma Globulin | 3%–12% of total proteins | Lower-yield | |
| Urine | |||
| Urine Osmolality | 50–1200 mOsm/kg | High-yield | |
| Urine Protein, Total (24h) | <150 mg/24h | Medium | |
| Urine Calcium (24h) | 100–300 mg/24h | Lower-yield | |
| Urine Oxalate (24h) | 8–40 µg/mL | Lower-yield | |
| Other Serum | |||
| Amylase | 25–125 U/L | High-yield | |
| Lipase | 13–60 U/L | High-yield | |
| Creatinine Clearance(Male) | 97–137 mL/min | Medium | |
| Creatinine Clearance(Female) | 88–128 mL/min | Medium | |
| Creatine Kinase (CK)(Male) | 25–90 U/L | High-yield | |
| Creatine Kinase (CK)(Female) | 10–70 U/L | High-yield | |
| Lactate Dehydrogenase (LDH) | 45–200 U/L | Medium | |
| Troponin I | ≤0.04 ng/mL | High-yield | |
| Body Mass Index (BMI)(Adult) | 19–25 kg/m² (normal) | Lower-yield | |
| Immunoglobulins | |||
| IgA | 76–390 mg/dL | Medium | |
| IgE | 0–380 IU/mL | Lower-yield | |
| IgG | 650–1500 mg/dL | Medium | |
| IgM | 50–300 mg/dL | Medium | |
| WBC Differential | |||
| Neutrophils, Segmented | 54–62 % | High-yield | |
| Neutrophils, Bands | 3%–5% | High-yield | |
| Lymphocytes | 25–33 % | High-yield | |
| Monocytes | 3–7 % | Medium | |
| Eosinophils | 1–3 % | High-yield | |
| Basophils | 0%–0.75% | Medium | |
| Blood Volume | |||
| Plasma Volume(Male) | 25–43 mL/kg | Lower-yield | |
| Plasma Volume(Female) | 28–45 mL/kg | Lower-yield | |
| Red Cell Volume(Male) | 20–36 mL/kg | Lower-yield | |
| Red Cell Volume(Female) | 19–31 mL/kg | Lower-yield | |
What the NBME lab values sheet is
NBME lab values come with the exam
The sheet is part of the exam software. On Step 1, Step 2 CK and Step 3 alike, any item reporting laboratory data keeps the NBME lab values one click away.
That single fact decides how to study NBME lab values: drill interpretation, not recall.
What the NBME lab values sheet covers
105 analytes in 14 panels. Serum electrolytes and renal chemistry, hepatic panel, lipids and iron studies open the NBME lab values list.
Endocrine, arterial blood gas and the complete blood count with its white-cell differential carry the next block of NBME lab values.
Coagulation, cerebrospinal fluid, urine, other serum chemistry, immunoglobulins and blood volume close the NBME lab values sheet out.
Which NBME lab values are worth memorising
About twenty. Opening the sheet costs seconds, and looking up the common NBME lab values forty times in a block wastes minutes you do not have.
Start with the four serum electrolytes, the NBME lab values that travel together: sodium 136–146, potassium 3.5–5.0, chloride 95–105, bicarbonate 22–28 mEq/L.
Add BUN 7–18 mg/dL, creatinine 0.6–1.2 mg/dL, fasting glucose 70–100 mg/dL and serum osmolality 275–295 mOsm/kg to that core of NBME lab values.
Arterial pH 7.35–7.45, PaCO₂ 33–45 mmHg and calcium 8.4–10.2 mg/dL finish the NBME lab values worth knowing cold.
Which NBME lab values to look up instead
Everything rarer. A misremembered ceiling is worse than no memory at all, and most NBME lab values are quoted too rarely to earn the space.
Urine oxalate, 17-ketosteroids and CSF gamma globulin are NBME lab values nobody should be carrying in their head.
NBME revises the sheet, so treat memorised NBME lab values as provisional and open the tutorial in your own testing interface before test day.
Where the NBME lab values PDF lives
NBME publishes the laboratory reference values on its own site, as a page and as a downloadable NBME lab values PDF.
Take it from there rather than from a re-hosted upload. Third-party copies of the NBME lab values drift, and a stale interval is worse than none.
What the NBME lab values PDF cannot do
A static NBME lab values PDF cannot tell you whether the 11.4 mg/dL calcium in front of you is high.
Nor can it be filtered to the coagulation panel while you read a bleeding vignette, and searching NBME lab values on a phone needs a page rather than a file.
That gap is what this page fills: the same NBME lab values, plus a comparison you can actually run on a number.
USMLE lab values and NBME lab values are one sheet
Both spellings describe one object. NBME writes and administers the USMLE examinations, and it supplies the NBME lab values used inside every one of them.
A single laboratory reference covers Step 1, Step 2 CK and Step 3, so USMLE lab values and NBME lab values name the same table.
Normal lab values USMLE, NBME laboratory reference values, the lab values sheet — every one of those phrases points at the NBME lab values in the directory above.
How the NBME lab values interpreter works
Pick a test and type a number. The tool compares it against the published bounds for that row of NBME lab values.
Back comes a direction (normal, low or high), a severity band, and the diagnoses that reading of the NBME lab values classically points to.
What the NBME lab values interpreter will not do
It does not convert NBME lab values between conventional and SI reference intervals, and it does not adjust for age, pregnancy or assay method.
And it names no diagnosis. The lists beside these NBME lab values are prompts for your own differential, not medical advice.
Where these NBME lab values come from
Bounds, units and panel groupings for these NBME lab values follow the reference sheet NBME publishes.
The notes and diagnosis lists around each of these NBME lab values are original study material written for this site, which is independent of NBME and USMLE.
How to read NBME lab values in a vignette
Read the whole panel of NBME lab values, not one row
A sodium of 128 mEq/L means very little until the two osmolality NBME lab values sit beside it.
The sheet groups tests into panels for that reason, and the directory above keeps the NBME lab values in the same groupings.
Flag every out-of-range result first without interpreting it, then ask which single process explains that pattern of NBME lab values.
Vignettes are written so one process does explain the set, which makes reading NBME lab values as a pattern faster than reading them one by one.
Serum electrolytes: read these NBME lab values together
A bicarbonate of 16 mEq/L is a different problem depending on which NBME lab values sit beside it — the anion gap and the PaCO₂.
Sodium, potassium, chloride and bicarbonate are the four NBME lab values most likely to appear together in one stem.
Arterial blood gas: three NBME lab values in order
Arterial pH 7.35–7.45, PaCO₂ 33–45 mmHg and PaO₂ 75–105 mmHg are the three NBME lab values that decide whether a disturbance is respiratory or metabolic.
Compensation is the second question, never the first. Name the primary disturbance, then check the companion NBME lab values moved the way they should.
Iron studies: three NBME lab values, one story
A low serum iron is ambiguous alone. TIBC 250–400 µg/dL and ferritin are the NBME lab values that decide what it means.
Ferritin is an acute-phase reactant, so a normal result during inflammation does not rule out an empty store — the classic trap in these NBME lab values.
Male and female ferritin intervals differ, 20–250 ng/mL against 10–120 ng/mL, so the directory carries both NBME lab values as separate rows.
Complete blood count: which NBME lab values sort an anaemia
MCV 80–100 µm³ sorts an anaemia faster than any of the other NBME lab values in the count.
Hemoglobin runs 13.5–17.5 g/dL in males and 12.0–16.0 g/dL in females, two NBME lab values a single number cannot cover.
Endocrine: the NBME lab values that settle each other
High calcium with a high intact PTH is primary hyperparathyroidism; with a suppressed PTH the same NBME lab values point at malignancy.
Two NBME lab values, one diagnosis, and the pattern repeats across the endocrine panel.
Total T4 rises with pregnancy or estrogen through thyroxine-binding globulin, so free T4 0.9–1.7 ng/dL is the NBME lab values reading that wins.
Hemoglobin A1c reads falsely low when red cells are short-lived and falsely high in iron deficiency: two traps in one of the most quoted NBME lab values.
Coagulation: two NBME lab values and a mixing study
PT 11–15 seconds and PTT 25–40 seconds are NBME lab values where a prolongation is obvious long before its cause is.
A prolonged PTT correcting on a mixing study is a factor deficiency; failing to correct points at an inhibitor, and no NBME lab values distinguish the two.
The NBME lab values give you the numbers. The mixing study is the step the vignette wants you to name next.
When NBME lab values are normal and still wrong
A creatinine of 1.1 mg/dL sits inside the NBME lab values interval and still means a large loss of filtration in a frail eighty-year-old with no muscle mass.
Reference intervals describe populations. The vignette describes a person, which is where NBME lab values stop being arithmetic.
Why some NBME lab values appear twice
Several analytes carry sex-specific or state-specific NBME lab values, and the sheet publishes them separately.
Creatinine clearance, ESR, hematocrit, creatine kinase and FSH all split, so each variant is its own row in these NBME lab values.
Where to practise reading NBME lab values
So practise reading values inside vignettes rather than drilling these NBME lab values as flashcards.
If a scored form rather than a set of NBME lab values is what you are holding, convert a practice form score, and for sourcing see where these intervals come from.
Frequently asked questions
Where these NBME lab values come from, and how much of the sheet you need in your head.
What are the NBME lab values?
NBME lab values are the laboratory reference intervals NBME publishes on its lab values sheet and shows on screen during the exam. This page holds all 105 of them across 14 panels.
Are NBME lab values given to you during the exam?
Yes. The sheet sits one click from any item reporting laboratory data and stays open for the whole block, so no NBME lab values have to come from memory.
How many NBME lab values should I memorise?
Around twenty. Sodium 136–146 mEq/L, potassium 3.5–5.0 mEq/L, bicarbonate 22–28 mEq/L and arterial pH 7.35–7.45 save you the seconds a lookup costs; rarer NBME lab values are safer looked up.
Are USMLE lab values the same as NBME lab values?
Same sheet, two spellings. NBME writes and administers the USMLE examinations, and one set of NBME lab values covers Step 1, Step 2 CK and Step 3.
Where can I download the NBME lab values PDF?
From NBME itself, which publishes the reference values on its own site as a page and as a file. Treat that document as the authority; re-hosted copies of NBME lab values go stale.
Why do some NBME lab values appear twice?
Because a few analytes carry sex-specific NBME lab values. Hemoglobin runs 13.5–17.5 g/dL for males and 12.0–16.0 g/dL for females, so each variant is its own row.
Can I export these NBME lab values?
Yes. The CSV download carries every row with its interval, unit and panel, which is enough to build flashcards or revise the NBME lab values offline.
Does this NBME lab values tool store what I type?
No. Search, filtering and NBME lab values interpretation all run in your browser. There is no account, no email step, and nothing you enter leaves the page.
Where to go next
Every tool here is free, needs no account, and runs entirely in your browser.
Every one of the 105 NBME lab values above is free to search, interpret and export, with no account and nothing uploaded.
Not affiliated with, endorsed by, or sponsored by the NBME® or USMLE®. Reference intervals are provided for study and are not medical advice.