What does the Phosphorus (Inorganic Phosphate) test measure?

Why is Phosphorus (Inorganic Phosphate) measured?

Serum phosphorus is a validated and routine measure used to detect hypophosphataemia and hyperphosphataemia, to monitor chronic kidney disease and mineral bone disorder, and to anticipate and manage refeeding syndrome. Its principal limitation is that it samples only the small extracellular fraction and therefore reflects total body phosphate stores poorly: levels shift acutely with transcellular movement driven by insulin, glucose, and pH, so a normal serum phosphorus does not exclude significant total body depletion. It is interpreted alongside calcium, parathyroid hormone, vitamin D, magnesium, and renal function rather than in isolation.

Reference ranges

Standard reference

Adults: 2.5–4.5 mg/dL (0.81–1.45 mmol/L); higher in children and adolescents

Functional medicine optimal

Mid-reference values are sometimes cited as favourable in functional medicine, though no standardised optimal applies

Units

mg/dL, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.