Pediatric Normal Lab Values by Age
Pediatric reference intervals shift markedly with age — especially in the first year — so a “normal adult” range will mislead at the cot-side. The tables below are typical adult-unit ranges for orientation; always interpret against your own laboratory’s age- and sex-partitioned intervals and assay method.
Complete blood count (CBC)
| Test | Newborn | Infant (1–12 mo) | Child (1–12 y) | Adolescent |
|---|---|---|---|---|
| Haemoglobin (g/dL) | 14.0–24.0 | 9.5–14.0 | 11.0–14.5 | 12.0–16.0 |
| Haematocrit (%) | 44–70 | 28–42 | 33–43 | 36–49 |
| WBC (×10⁹/L) | 9.0–30.0 | 6.0–17.5 | 5.0–15.0 | 4.5–13.0 |
| Platelets (×10⁹/L) | 150–450 | 150–450 | 150–450 | 150–450 |
| MCV (fL) | 95–120 | 70–86 | 76–90 | 78–95 |
Physiologic nadir of haemoglobin occurs at ~8–12 weeks (term infants) — a low Hb here is often expected, not pathologic.
Electrolytes
| Test | Reference range |
|---|---|
| Sodium (mmol/L) | 135–145 |
| Potassium (mmol/L) | 3.5–5.0 (newborn up to 6.0) |
| Chloride (mmol/L) | 98–107 |
| Bicarbonate (mmol/L) | 20–28 |
| Calcium, total (mg/dL) | 8.8–10.8 (newborn 7.6–10.4) |
| Magnesium (mg/dL) | 1.7–2.4 |
| Phosphate (mg/dL) | 4.5–6.5 (infant); 3.5–5.5 (child) |
Renal function
| Test | Infant | Child | Adolescent |
|---|---|---|---|
| Urea / BUN (mg/dL) | 4–16 | 5–18 | 7–20 |
| Creatinine (mg/dL) | 0.2–0.4 | 0.3–0.7 | 0.5–1.0 |
| Glucose, fasting (mg/dL) | 60–100 | 70–100 | 70–100 |
Creatinine rises with muscle mass through childhood — a “normal adult” creatinine in a toddler may signal significant renal impairment.
Liver function tests (LFT)
| Test | Infant | Child / Adolescent |
|---|---|---|
| ALT (U/L) | 5–35 | 5–40 |
| AST (U/L) | 20–65 | 10–40 |
| Total bilirubin (mg/dL) | <1.0 (after neonatal period) | 0.2–1.0 |
| Direct bilirubin (mg/dL) | <0.3 | <0.3 |
| ALP (U/L) | 150–420 | 100–400 (peaks at growth spurts) |
| Albumin (g/dL) | 2.8–4.4 | 3.5–5.0 |
| GGT (U/L) | 8–127 (falls rapidly after infancy) | 5–25 |
Alkaline phosphatase is physiologically high during rapid bone growth (infancy and puberty) — do not over-call this as cholestasis.
Reminders
- Neonatal ranges differ sharply from infant ranges; the first 28 days are their own category for almost every analyte.
- Direct (conjugated) hyperbilirubinaemia is never physiologic — investigate any direct bilirubin >0.3 mg/dL or >20% of total.
- Spurious hyperkalaemia from haemolysed or heel-prick samples is common in infants — repeat before acting.
For normal vital signs by age, see the companion vital-signs cheat-sheet.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.