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Calcium in Urine Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Calcium in Urine Test

A calcium in urine test measures the amount of calcium excreted in your urine to help diagnose kidney stones, parathyroid disorders, and bone diseases.

Overview

When blood calcium levels are high, the body may store the excess in bones or excrete it through urine and stool. The parathyroid glands play a critical role in this process by producing parathyroid hormones (PTH), which regulate calcium levels by signaling the bones, intestines, and kidneys. A calcium in urine test helps determine if these systems are functioning correctly.

What is it used for?

This test is used to:

  • Diagnose the cause of kidney stones, which are often composed of calcium.
  • Monitor kidney function.
  • Evaluate parathyroid gland activity.
  • Investigate the cause of bone diseases like osteoporosis.
  • Follow up on abnormal results from a calcium blood test.

Why do I need this test?

You may need this test if you have symptoms of a kidney stone, such as sharp pain in the back or abdomen, blood in the urine, or painful/frequent urination. It is also used to evaluate conditions like hyperparathyroidism (overactive glands) or hypoparathyroidism (underactive glands), the latter of which can cause symptoms like tingling fingers, muscle cramps, and fatigue.

What happens during the test?

This is a 24-hour urine sample test. The process involves:

  • Discarding the first morning urine and noting the time.
  • Collecting all subsequent urine for the next 24 hours in a provided container.
  • Storing the container in a refrigerator or cooler with ice throughout the collection period.
  • Collecting the final sample exactly 24 hours after the start time.
  • Returning the container to the laboratory or provider's office.

Understanding Results

Higher than normal levels may indicate kidney stones, hyperparathyroidism, certain cancers, or bone disorders like Paget's disease. Lower than normal levels may indicate kidney disease, hypoparathyroidism, malnutrition, or vitamin D/magnesium deficiency.

Results can be influenced by diet (especially sodium intake), supplements, and medications like diuretics. As with the blood test, this procedure does not measure bone density; a DEXA scan is the standard for assessing bone mineral content.

Frequently Asked Questions

single random urine sample is highly variable and does not accurately reflect your body's total calcium excretion over a day. Diet, hydration levels, and time of day significantly impact calcium concentration in any single void. A 24-hour collection provides a comprehensive measure of how much calcium your kidneys are filtering and excreting over a full cycle, which is critical for diagnosing conditions like hypercalciuria (excessive calcium in urine) that contribute to kidney stone formation.
The most common reasons for a failed test are missing the start or end time, forgetting to collect a void, or improper storage. To prevent this, set two alarms: one for the start time (when you discard the first morning urine) and one for the exact end time 24 hours later. Keep the collection container with you at all times, including in the bathroom, and store it in the refrigerator or on ice as instructed. Do not add any preservatives unless specifically provided by the lab.
You should maintain your usual diet and fluid intake unless your provider gives specific instructions to restrict certain foods. Drastic changes in salt, protein, or calcium intake on the day of the test can skew the results and make it difficult to determine your baseline excretion. If you are on a specific diet for medical reasons, continue it as normal. The goal is to capture a representative sample of your typical daily calcium handling.
This condition is often called idiopathic hypercalciuria. It means your kidneys are excreting more calcium than usual, even though your blood levels are within the normal range. This is a significant risk factor for developing calcium kidney stones. It may also indicate that your body is absorbing too much calcium from the gut or that your bones are losing calcium faster than they are being replaced. Your provider will likely recommend dietary modifications, such as reducing sodium and animal protein, and increasing fluid intake to manage this risk.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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