What does the Urinary Calcium test measure?

Why is Urinary Calcium measured?

Random urine calcium offers a convenient, though less precise, estimate of renal calcium handling in the investigation of nephrolithiasis, hypercalciuria, and disorders of calcium homeostasis. Elevated spot calcium or calcium:creatinine ratio suggests hypercalciuria and guides stone-risk assessment, while low urinary calcium may point to malabsorption, hypoparathyroidism, or vitamin D deficiency. Because dietary intake and hydration vary throughout the day, the random sample is most useful as a screening or monitoring tool rather than for definitive diagnosis, which often requires a 24-hour collection and concurrent serum studies.

Reference ranges

Standard reference

Random urine 0–20 mg/dL; calcium:creatinine ratio typically <0.20 mg/mg or <0.57 mmol/mmol.

Functional medicine optimal

Functional medicine practitioners may interpret a calcium:creatinine ratio above 0.15 mg/mg as increased stone risk, but individualised thresholds depend on dietary intake, fluid intake, and the presence of other lithogenic factors.

Units

mg/dL, mmol/L

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