Table 3.

Sex- and age-specific serum electrolyte reference intervals in healthy children aged 2–14 years (n = 1391).

Analytes	Age group	Sex group	No. of samples	Lower limit	Upper limit	Confidence interval for lower limit	Confidence interval for upper limit
Potassium (mmol/L)	2 to < 4 years	F + M	452	3.96	5.39	3.89–4.07	5.29–5.47
	4 to < 12 years	F + M	735	3.73	5.27	3.66–3.80	5.14–5.36
	12 to < 15 years	F + M	204	4.14	5.39	4.12–4.18	5.27–5.43
Sodium (mmol/L)	2 to < 9 years	F + M	989	136.4	146.8	134.9–138.2	146.2–147.1
	9 to < 11 years	F + M	142	121.8	146.4	117.8–125.8	145.7–147.1
	11 to < 13 years	F + M	119	136.9	148.6	131.8–142.0	147.3–149.9
	13 to < 15 years	F	56	134.5	146.4	134.1–135.5	145.0–147.6
		M	85	138.6	149.2	138.2–139.9	147.9–149.9
Chlorine (mmol/L)	2 to < 11 years	F + M	1131	94.6	106.4	93.4–96.0	106.0–106.6
	11 to < 13 years	F + M	119	98.4	108.8	95.3–101.5	107.5–110.2
	13 to < 15 years	F	56	93.9	107.4	93.4–96.8	102.6–108.7
		M	85	97.1	107.5	96.6–98.2	105.7–108.9
Calcium (mmol/L)	2 years	F + M	196	2.00	2.64	1.91–2.09	2.60–2.68
	3 to < 13 years	F + M	1054	1.95	2.57	1.91–1.99	2.55–2.59
	13 to < 15 years	F	56	1.96	2.32	1.94–2.08	2.28–2.34
		M	85	1.96	2.37	1.92–2.02	2.34–2.40
Phosphorus (mmol/L)	2 years	F + M	196	1.39	2.65	1.35–1.43	1.96–3.30
	3 to < 8 years	F + M	738	1.32	2.03	1.30–1.34	1.97–2.09
	8 to < 11 years	F + M	197	1.26	1.89	1.22–1.30	1.81–1.97
	11 to < 13 years	F + M	119	1.29	1.91	1.23–1.35	1.81–2.01
	13 to < 15 years	F	56	1.10	1.61	1.07–1.17	1.59–1.63
		M	85	1.00	1.99	0.97–1.05	1.59–1.99

M, male; F, female.