Common Lab Values
Adult reference ranges (each lab's own ranges vary slightly: use yours)
Complete blood count
| WBC | 5,000–10,000/mm³ |
| RBC | Men 4.7–6.1 · Women 4.2–5.4 million/mm³ |
| Hemoglobin | Men 14–18 · Women 12–16 g/dL |
| Hematocrit | Men 42–52% · Women 37–47% |
| Platelets | 150,000–400,000/mm³ (bleeding risk <50,000; spontaneous bleeding <20,000) |
| ANC | >1,500 normal; <500 severe neutropenia |
Basic metabolic panel
| Sodium | 135–145 mEq/L |
| Potassium | 3.5–5.0 mEq/L |
| Chloride | 98–106 mEq/L |
| Bicarbonate (CO₂) | 22–26 mEq/L (some labs 23–29) |
| BUN | 10–20 mg/dL |
| Creatinine | ~0.6–1.2 mg/dL |
| Glucose (fasting) | 70–99 mg/dL |
| Calcium | 9.0–10.5 mg/dL (some labs 8.5–10.5) |
Other electrolytes and kidney
| Magnesium | 1.5–2.5 mg/dL (1.3–2.1 mEq/L) |
| Phosphorus | 2.5–4.5 mg/dL |
| eGFR | ≥90 mL/min/1.73 m² normal; <60 for 3 months = CKD |
| Serum osmolality | 275–295 mOsm/kg |
| Urine specific gravity | 1.005–1.030 (high = concentrated) |
| Uric acid | Men 4.0–8.5 · Women 2.7–7.3 mg/dL |
Coagulation
| PT | 11–12.5 sec |
| INR | 0.8–1.1 (warfarin goal usually 2–3) |
| aPTT | 30–40 sec |
| Fibrinogen | 200–400 mg/dL (low in DIC) |
| D-dimer | Below lab cut-off (high = clot breakdown; non-specific) |
Liver and pancreas
| ALT / AST | ~4–36 / 0–35 U/L (ranges vary) |
| Alkaline phosphatase | 30–120 U/L |
| Total bilirubin | 0.3–1.0 mg/dL |
| Albumin | 3.5–5.0 g/dL |
| Ammonia | Lab-specific (roughly 15–45 mcg/dL); high in hepatic encephalopathy |
| Lipase | Lab-specific; ≥3× upper limit supports pancreatitis |
Others
| Hemoglobin A1C | <5.7% normal · 5.7–6.4% prediabetes · ≥6.5% diabetes |
| TSH | ~0.4–4.0 mIU/L |
| Lactate | <2 mmol/L (≥4 in sepsis = shock risk) |
| BNP | <100 pg/mL |
| Troponin (high-sensitivity) | Below the lab's 99th percentile; rising = heart injury |
| CRP / ESR | Markers of inflammation |
Priority: report right away
K⁺ <3.0 or >5.5–6.0 · Na⁺ <125 or >155 · glucose <70 or very high · platelets <50,000 · ANC <500 · Hgb <7 · INR well above goal · positive blood cultures · troponin rising · lactate ≥4. Facilities set their own "critical value" lists.