What it is (overview)

A 24-hour urine calcium test (also called 24 HRS Urine for Calcium or urinary calcium test) measures how much calcium your kidneys release into your urine over a full day. Unlike a single “spot” urine sample, a 24-hour collection provides a more accurate picture of daily calcium excretion because calcium levels can vary throughout the day based on meals, fluids, activity, and hormones.

Calcium is an important electrolyte involved in bone strength, muscle and nerve function, and many metabolic processes. Normally, your body balances calcium by coordinating absorption from the gut, storage in bones, and removal through the kidneys. This test helps evaluate that balance (your calcium metabolism) by showing whether you are losing too much or too little calcium in the urine.

What results can mean in plain language:

High urine calcium (often called hypercalciuria) can mean your kidneys are releasing more calcium than expected. This may raise the risk of kidney stones (especially calcium oxalate or calcium phosphate stones) and, in some cases, may be linked to bone mineral loss over time. Causes can include diet factors (high sodium or high animal protein intake), certain medications, overactive parathyroid glands, vitamin D–related issues, and other metabolic or kidney conditions.

Low urine calcium may occur when the body is not absorbing enough calcium from food, when dietary calcium intake is very low, or with certain kidney and hormonal conditions. Your clinician interprets the result alongside blood tests (such as serum calcium, parathyroid hormone, vitamin D) and other urine studies to understand the full picture.

Because urine calcium is influenced by hydration, diet, supplements, and medicines, your provider may give instructions about what to avoid before and during the collection. Accurate timing and collecting all urine for 24 hours are essential for reliable results.

When & why it's usually done

Doctors commonly order a 24-hour urine calcium test when they need to understand why calcium is appearing in the urine at a certain level or to investigate problems related to renal function, stones, or bone health.

This test is often recommended if you have:

Kidney stone concerns—especially if you have had one or more stones, a strong family history, or stones that recur. Measuring urinary calcium helps identify a common, treatable risk factor for stone formation and can guide prevention strategies.

Symptoms or lab findings suggesting calcium imbalance—such as unexplained high or low blood calcium, frequent urination, excessive thirst, constipation, fatigue, muscle weakness, or bone pain (symptoms vary and are not specific).

Bone health concerns—including low bone density, suspected osteoporosis, or fractures that occur with minimal trauma. Excess calcium loss in urine can contribute to reduced bone mineral density in some people.

Evaluation of metabolism and endocrine causes—to help assess conditions affecting calcium regulation, such as parathyroid disorders or vitamin D–related problems. The test is also used to monitor how treatment or dietary changes impact urinary calcium.

Medication or supplement monitoring—some medicines and supplements can change urinary calcium (for example, certain diuretics, calcium or vitamin D supplements, and others). Your clinician may use this test to tailor dose and reduce stone risk.

In many cases, the 24-hour urine calcium test is part of a broader 24-hour urine metabolic evaluation for kidney stones that may also include urine volume, sodium, citrate, oxalate, uric acid, creatinine, and other electrolytes.

Common diseases related to it

• Kidney stones (calcium oxalate stones and calcium phosphate stones)
• Hypercalciuria (high urinary calcium)
• Primary hyperparathyroidism (overactive parathyroid glands)
• Osteoporosis and low bone mineral density
• Vitamin D excess or vitamin D deficiency–related calcium disorders
• Chronic kidney disease and other renal tubular disorders affecting calcium handling
• Sarcoidosis and other granulomatous diseases that can raise calcium levels
• Malabsorption syndromes (reduced calcium absorption from the gut)

Health goals where it may help

• Reducing the risk of recurrent kidney stones through targeted prevention (diet, hydration, and medication planning)
• Monitoring calcium metabolism and electrolyte balance as part of a metabolic health evaluation
• Supporting bone health goals, including osteoporosis screening and prevention strategies
• Assessing renal function and how well the kidneys regulate minerals
• Guiding safe use of calcium and vitamin D supplements, especially in people at risk for stones
• Tracking response to treatment for causes of abnormal calcium levels (for example, endocrine or metabolic therapies)