Table 3.

Normal age-based serum calcium and phosphorus levels in children²⁵

Age	Age-based serum calcium (mg/dl)	Age-based serum phosphorus (mg/dl)
0–3 mo	8.8–11.3	4.8–7.4
1–5 yr	9.4–10.8	4.5–6.5
6–12 yr	9.4–10.3	3.6–5.8
13–20 yr	8.8–10.2	2.3–4.5

To convert units: calcium 1 mg/dl = 0.25 mmol/l; phosphorus 1 mg/dl = 0.32 mmol/l.