A urine calcium test is done to measure how much calcium is passed out of the body through urine. The test is also known as the urinary Ca+2 test.
Calcium is the most common mineral in the body. All cells throughout the body use calcium for various functions. The body uses calcium to build and repair bones and teeth. Calcium also helps nerves, the heart, and muscles function properly, and helps blood to clot.
Most of the calcium in the body is stored in bones. The remainder is found in the blood.
When calcium levels in the blood get too low, the bones release enough calcium to bring the level in the blood back to normal. When calcium levels get too high, the surplus of calcium is either stored in bones or expelled from the body through your urine or stool.
The amount of calcium that’s in your body depends on the following factors:
- amount of calcium taken in from food
- amount of calcium and vitamin D absorbed through the intestines
- level of phosphate in the body
- certain hormone levels — such as estrogen, calcitonin, and parathyroid hormone
Most often, people who have high or low levels of calcium do not show any symptoms. Calcium levels need to be extremely high or extremely low to show symptoms.
Reasons to perform a urine calcium test include:
- evaluating whether high calcium levels in the urine resulted in the development of a kidney stone
- evaluating whether your dietary intake of calcium is high enough
- evaluating how well your intestines are absorbing calcium
- detecting conditions that lead to calcium loss from your bones
- evaluating how well your kidneys are functioning
- looking for problems with the parathyroid gland
In preparation for the urinary calcium test, your doctor may instruct you to stop taking medications that could affect the test results. In addition, your doctor may ask you to follow a diet with a specific level of calcium for several days leading up to the test.
If the urine sample is being collected from your infant, your child’s doctor will provide special collection bags with instructions on how the urine should be collected.
A urine calcium test measures the amount of calcium in a sample taken from all the urine that is produced in a 24–hour period. The test lasts from the morning of one day to the morning of the next day.
These steps are usually followed for the urine test:
- On the first day, you urinate after awakening and do not save the urine.
- For the next 24 hours, you collect all subsequent urine in a container provided by a health professional.
- You then close the container and keep it refrigerated during the 24-hour collection period. Be sure to put your name on the container, as well as the date and time the test was completed.
- On day two, you urinate into the container after awakening.
- Return the sample as instructed by your doctor or other health professional.
There are no risks associated with the urine calcium test.
The amount of calcium in the urine of someone eating a normal diet is 100 to 300 mg/day*. A diet that is low in calcium results in 50 to 150 mg/day of calcium in the urine.
*mg/day = milligrams per day
If calcium levels in the urine are abnormally high, it may be a sign of:
- hyperparathyroidism: a condition where the parathyroid gland produces too much parathyroid hormone, which may also cause fatigue, back pain, and sore bones
- milk-alkali syndrome: a condition that results from taking too much calcium, usually seen in older women who take calcium to prevent osteoporosis
- idiopathic hypercalciuria: too much calcium in your urine without a reason
- sarcoidosis: a disease in which inflammation occurs in the lymph nodes, lungs, liver, eyes, skin, or other tissues
- renal tubular acidosis: high acid levels in the blood because the kidneys do not make the urine acidic enough
- vitamin D intoxication: too much vitamin D in your body
- use of loop diuretics: a type of water pill that works on one part of the kidney to increase water loss by the kidney
- kidney failure
If calcium levels in the urine are abnormally low, it may be a sign of:
- malabsorption disorders: such as vomiting or diarrhea, because the food nutrients have not been properly digested
- vitamin D deficiency
- hypoparathyroidism: a disease in which the parathyroid doesn’t produce enough of a certain hormone to keep calcium and phosphorus at proper levels
- use of thiazide diuretics