Calcium 24 Hour Test

Calcium is essential for bone structure, muscle contraction, nerve signaling, and blood clotting. The kidneys play a key role in maintaining calcium balance by filtering and reabsorbing calcium under the influence of parathyroid hormone and vitamin D. A 24 hour urine calcium test measures total daily calcium excretion, which is critical for understanding kidney stone risk and bone health.

High urinary calcium, a condition called hypercalciuria, is one of the strongest risk factors for calcium based kidney stones. It can occur even when blood calcium levels are normal and may be driven by high sodium intake, excess calcium absorption from the gut, bone loss, or hormonal imbalance. Low urinary calcium may reflect low intake, poor absorption, or increased renal conservation, which can also signal altered bone metabolism. Compared with blood calcium, which is tightly regulated, the 24 hour urine test reveals how the body is truly handling calcium over time.