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Calcium - urine

Definition

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

Alternative Names

Urinary Ca+2

How the test is performed

A 24-hour urine sample is usually needed:

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

A urine collection bag is needed for infants. This is a plastic bag with a sticky 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 the 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 move the bag. The infant should be checked often. Change the bag after the infant has urinated into it. Drain the urine into the container given to you by your health care provider and deliver it to the laboratory or doctor's office as soon as possible.

How to prepare for the test

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, you may need a couple of extra collection bags.

How the test will feel

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

Why the test is performed

Urine calcium levels can help your doctor:

  • Decide on the best treatment for the most common type of kidney stone, which is made of calcium. This type of stone may occur when the kidney leaks too much calcium into the urine.
  • Monitor someone who has a problem with the parathyroid gland, which helps control calcium levels in the blood and urine.

Normal Values

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

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

Note: mg/day = milligrams per day

What abnormal results mean

High levels of urine calcium (above 300 mg/day) may be due to:

  • Chronic kidney disease
  • Leaking of urine from the kidneys, which causes calcium kidney stones
  • Sarcoidosis
  • Takiong too much calcium
  • Too much production of parathyroid hormone by the parathyroid glands in the neck
  • Use of water pills called loop diuretics
  • Very highvitamin D levels

Low levels of urine calcium may be due to:

What the risks are

There are no risks.

References

Bringhurst FR, Demay MB, Kronenberg HM. Hormones and disorders of mineral metabolism. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 28.

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.


Review Date: 6/1/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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