UrinCalcium

UrinCalcium, commonly referred to as urinary calcium, is the amount of calcium excreted in urine over a given period. Clinically, it is used to assess calcium metabolism and to evaluate conditions such as nephrolithiasis (kidney stones) and osteoporosis risk. It is commonly expressed as mg/day or mmol/day and can be reported as 24-hour urinary calcium excretion or as a spot urine calcium-to-creatinine ratio.

Measurement: The standard method is a 24-hour urine collection, often paired with serum calcium and parathyroid hormone testing. A spot urine test uses calcium-to-creatinine ratio to estimate 24-hour excretion; results depend on collection completeness and recent dietary intake of calcium and sodium. Proper patient instruction is essential.

Clinical significance: Elevated urinary calcium (hypercalciuria) can predispose to calcium-containing kidney stones and may reflect overproduction of calcium or renal wasting. It can occur with primary hyperparathyroidism, certain cancers, vitamin D excess, renal tubular disorders, or after excessive dietary calcium or sodium. Low urinary calcium (hypocalciuria) can occur with familial hypocalciuric hypercalcemia or thiazide diuretic use; loop diuretics raise calciuria.

Interpretation: Urinary calcium results must be interpreted in context of serum calcium, renal function, age, and dietary intake. Repeated measurements or repeat collections may be needed due to day-to-day variation.

See also: Calcium metabolism, Hypercalciuria, Nephrolithiasis, Osteoporosis.