This test measures the amount of calcium in urine. All cells need calcium in order to work. Calcium helps build strong bones and teeth. It is important for heart function, and helps with muscle contraction, nerve signaling, and blood clotting.

See also: Calcium - blood

A 24-hour urine sample is generally needed:

• On day 1, urinate into the toilet upon arising in the morning.
• Collect all subsequent urine (in a special container) for the next 24-hours.
• On day 2, urinate into the container in the morning upon arising.
• Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

A urine collection bag is needed for infants. This is a plastic bag with an adhesive paper on one end. Wash the area around the child's urethra. For boys, place the entire penis in the bag and attach the adhesive to nearby skin. For girls, place the bag over the labia and secure into place with the adhesive. You can place a diaper over the bag.

This procedure may take a couple of attempts -- lively infants can displace the bag. The infant should be checked frequently. Change the bag after the infant has urinated into it. Drain the urine into the container provided by your health care provider and deliver it to the laboratory or doctor's office as soon as possible.

Your doctor may tell you to temporarily stop taking any drugs that may affect the test results.

Drugs that may increase urine calcium measurements include antacids, anticonvulsants, carbonic anhydrase inhibitor diuretics, and loop diuretics.

Drugs that may decrease urine calcium measurements include adrenocorticosteroids, birth control pills, and thiazide diuretics.

NEVER stop taking any medicine without first talking to your doctor.

If the 24-urine collection is being taken from an infant, a couple of extra collection bags may be necessary.

The test involves only normal urination, and there is no discomfort.

This test is used to diagnose or monitor diseases of the parathyroid gland or kidneys, which can cause a calcium control disorder. If there is not enough calcium in your body fluids, it can lead to hyperexcited nerves and muscles. Too much calcium has the opposite effect.

The most common type of kidney stone contains calcium. This test may be used to diagnose such stones.

If a person is eating a normal diet, the expected amount of calcium in the urine is 100 to 300 mg/day. If eating a diet low in calcium, the amount of calcium in the urine will be 50 to 150 mg/day.

Note: mg/day = milligrams per day

High levels of urine calcium may be due to:

• Hyperparathyroidism
• Idiopathic hypercalciuria
• Kidney failure
• Milk-alkali syndrome
• Renal tubular acidosis
• Sarcoidosis
• Use of loop diuretics
• Vitamin D intoxication

Low levels of urine calcium may be due to:

• Hypoparathyroidism
• Malabsorption disorders
• Use of thiazide diuretics
• Vitamin D deficiency

There are no risks.

Wysolmerski JJ, Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 266.