Blood (Serum) Calcium Level Test

What is the blood calcium test?

This test measures the amount of calcium in your blood. Calcium is the most abundant mineral in the body. Your body needs calcium for normal functioning of your nerves and muscles, including the most important muscle of all, your heart. Calcium is also important for healthy bones and teeth. The amount of calcium in your blood is carefully controlled by your body's hormonal (glandular) system.

Your body gets calcium when you eat or drink dairy products, some vegetables (such as broccoli), and some calcium-fortified foods. You can take pills containing calcium. You also need vitamin D so your body can absorb calcium from the foods you eat.

Most of the calcium in your body is in your bones. The blood calcium test measures only the small amount of calcium in your blood. This test doesn't measure the amount of calcium in your bones. A procedure similar to an x-ray called a bone density test can measure the calcium in your bones.

Why is this test done?

The level of calcium in your blood may be measured to look for or check certain medical conditions, such as:

• bone disorders
• endocrine disorders (hormone problems)
• blood-clotting problems
• kidney disease
• irregular heartbeat.

The test may be done because you have symptoms of low calcium (hypocalcemia), such as muscle spasm, cramping, and twitching. You may also have numbness and tingling.

How do I prepare for this test?

• You don't need to fast or limit your activity before the test.
• You may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your health care provider knows about any medicines, herbs, or supplements that you are taking. Don't stop any of your regular medicines without first consulting with your provider.
• Talk to your provider if you have any questions.

How is the test done?

A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab.

Having this test will take just a few minutes of your time. There is no risk of getting AIDS, hepatitis, or any other blood-borne disease from this test.

How will I get the test result?

Ask your health care provider when and how you will get the result of your test.

What does the test result mean?

A normal blood calcium range for adults in most labs is 8.5 to 10.5 milligrams per deciliter (mg/dL). The normal range may vary slightly from lab to lab. Normal ranges are usually shown next to your results in the lab report.

Some of the reasons your blood level of calcium may be higher than normal are:

• You have taken a lot of vitamins A and D.
• You take certain medicines (such as some diuretics, also called "water pills," used to treat high blood pressure).
• You have been at bed rest for a long time.
• Your parathyroid gland is making too much parathyroid hormone.
• You have a kind of cancer that releases substances similar to parathyroid hormone (some types of breast, kidney, and lung cancer, for example).

Some of the reasons your blood level of calcium may be lower than normal are:

• Your body needs more vitamin D or the mineral magnesium.
• You don't get enough calcium from your diet.
• Your intestines are not absorbing calcium.
• You take certain medicines (such as cimetidine, a drug that makes your stomach produce less acid).
• Your parathyroid gland is not making enough parathyroid hormone.
• You have been drinking too much alcohol.
• You have kidney disease.
• Your pancreas is inflamed.

Your body will take calcium from your bones if the calcium level in your blood is low. So even if you have severe osteoporosis (bone-thinning) your blood level of calcium may be normal.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your heath care provider about your result and ask questions.

If your test results are not normal, ask your provider:

• if you need additional tests
• what you can do to work toward a normal value
• when you need to be tested again.