What does the 24-Hour Urinary Calcium Excretion test measure?

Why is 24-Hour Urinary Calcium Excretion measured?

Elevated 24-hour urinary calcium (hypercalciuria) is the most common metabolic risk factor for calcium-containing kidney stones and may signal primary hyperparathyroidism, excessive vitamin D, renal phosphate leak, or idiopathic hypercalciuria. Low excretion (hypocalciuria) occurs with hypoparathyroidism, vitamin D deficiency, malabsorption, thiazide diuretics, and familial hypocalciuric hypercalcaemia. The test is essential for stone-risk stratification, guiding dietary and pharmacological interventions, and distinguishing renal from non-renal causes of hypercalcaemia.

Reference ranges

Standard reference

Approximately 100–300 mg/24 h (2.5–7.5 mmol/24 h); sex- and diet-dependent.

Functional medicine optimal

Stone-prevention guidelines often target urinary calcium below 200 mg/24 h on a controlled sodium and protein intake, though this threshold is not universally adopted and must be interpreted with dietary context.

Units

mg/24 h, mmol/24 h

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