Normal Lab Values
The sourced reference intervals from CARE's lab-values page, with units, sources and the variation notes kept.
CARE Nursing · carenursingprep.com
Normal Lab Values
Electrolytes
| Sodium (Na⁺) | 136–145 mEq/L |
|---|---|
| Potassium (K⁺) | 3.5–5.0 mEq/LSources differ: Serum and plasma potassium differ by roughly 0.2–0.4 mmol/L, yet most laboratories publish one range for both. |
| Chloride (Cl⁻) | 98–106 mEq/L |
| Calcium (Ca²⁺), total | 8.6–10.2 mg/dL |
| Magnesium (Mg²⁺) | 1.6–2.6 mg/dL |
Complete blood count
| Hemoglobin (Hgb) | Female 12–16 · Male 14–18 g/dLSources differ: Sources differ on the male range: ABIM gives 14–18 g/dL, MedlinePlus 13–18. WHO's anaemia cut-offs are different again — and are adjusted for altitude and smoking. |
|---|---|
| Hematocrit (Hct) | Female 37–47 · Male 42–50 %Sources differ: The clearest example on this page that no single normal range exists. For adult males, ABIM gives 42–50%, MedlinePlus 40–55% and StatPearls 37–48% — a 22-point spread at the top end across three authoritative sources. |
| White blood cell count (WBC) | 4,000–11,000 /μLSources differ: Reported in three different unit systems across sources — /μL, /mm³ and ×10⁹/L — which look like different numbers but are the same value. |
| Platelet count | 150,000–450,000 /μLSources differ: ABIM's upper limit is 450,000/μL; several nursing sources publish 400,000. |
Renal function
| Blood urea nitrogen (BUN) | 8–20 mg/dL |
|---|---|
| Creatinine | Female 0.50–1.10 · Male 0.70–1.30 mg/dLSources differ: MedlinePlus contradicts itself here: its basic-metabolic-panel article gives 0.8–1.2 mg/dL with no sex split, while its dedicated creatinine article gives female 0.5–0.95 and male 0.7–1.3. |
Liver function
| Albumin | 3.5–5.5 g/dL |
|---|---|
| Bilirubin, total | 0.3–1.0 mg/dL |
| Aspartate aminotransferase (AST) | 10–40 U/L |
| Alkaline phosphatase (ALP) | 30–120 U/L |
Arterial blood gases
| pH, arterial | 7.38–7.44Sources differ: This is the value most worth understanding. ABIM's exam sheet gives 7.38–7.44; nursing teaching almost universally uses 7.35–7.45. Neither is wrong — they are different reference populations and methods — but a student taught 7.35 as a hard boundary will mis-read an item built on the narrower range. |
|---|---|
| PaCO₂, arterial | 38–42 mm HgSources differ: ABIM gives 38–42 mm Hg; nursing convention teaches 35–45. |
| PaO₂, arterial | 75–100 mm Hg |
| Bicarbonate (HCO₃⁻), arterial | 23–26 mEq/LSources differ: ABIM lists arterial bicarbonate as 23–26 mEq/L and serum bicarbonate separately — legitimately, because they are different specimens and methods. A single 'bicarbonate' row that ignores the specimen is hiding a real distinction. |
| Oxygen saturation, arterial | ≥95 % |
Coagulation
| Prothrombin time (PT) | 11–13 seconds |
|---|---|
| Activated partial thromboplastin time (aPTT) | 25–35 seconds |
Cardiac markers
| Troponin I, cardiac | ≤0.04 ng/mLSources differ: Troponin has no universal normal value and CARE will not publish one as if it did. There is no primary reference material for cardiac troponin I, so assays cannot be standardised against each other: three high-sensitivity assays measured on one reference population produced 99th-percentile limits of roughly 10, 17 and 17 ng/L, and another comparison gave 21, 31 and 28. Your laboratory's own limit is the only one that applies, and modern limits are sex-specific. |
|---|
Glucose
| Hemoglobin A1c | 4.0–5.6 % |
|---|
Endocrine
| Thyroid-stimulating hormone (TSH) | 0.5–4.0 μU/mL |
|---|
Guideline thresholds — not reference intervals
These are decision points set by guideline committees, not laboratory reference ranges. They do not vary by laboratory, but they do change when the committee changes them.
| Hemoglobin A1c — Normal | below 5.7%Set by American Diabetes Association, restated by NIDDK |
|---|---|
| Hemoglobin A1c — Prediabetes | 5.7% to 6.4%Set by American Diabetes Association, restated by NIDDK |
| Hemoglobin A1c — Diabetes | 6.5% or aboveSet by American Diabetes Association, restated by NIDDK |
| Fasting plasma glucose — Normal | 99 mg/dL or belowSet by American Diabetes Association, restated by NIDDK |
| Fasting plasma glucose — Prediabetes | 100 to 125 mg/dLSet by American Diabetes Association, restated by NIDDK |
| Fasting plasma glucose — Diabetes | 126 mg/dL or aboveSet by American Diabetes Association, restated by NIDDK |
A reference interval is the middle 95% of a healthy population on one laboratory's assay — 5% of healthy people fall outside it by design, and laboratories legitimately differ. Interpret any result against the range printed on that patient's own report. NCSBN states the NCLEX supplies the reference range within items containing a numeric lab value.
Sources
- ABIM Laboratory Test Reference Ranges, revised January 2026 — read 2026-09-03
- NIDDK, Diabetes Tests & Diagnosis — read 2026-09-03