The calcium blood test measures the level of calcium in the blood.
This article discusses the test to measure the total amount of calcium in your blood. About one half of the calcium in the blood is attached to proteins, mainly albumin.
A separate test that measures calcium that is not attached to proteins in your blood is sometimes performed. Such calcium is called free or ionized calcium.
Calcium can also be measured in the urine.
A blood sample is needed.
Your health care provider may tell you to temporarily stop taking certain medicines that can affect the test. These medicines may include:
Drinking too much milk (2 or more quarts or 2 liters a day or a large amount of other dairy products) or taking too much vitamin D as a dietary supplement can also increase blood calcium levels.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
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.
Your doctor may order this test if you have signs or symptoms of:
Your doctor may also order this test if you have been on bed rest for a long time.
Normal values range from 8.5 to 10.2 mg/dL (2.13 to 2.55 millimol/L).
Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.
A higher than normal level may be due to a number of health conditions. Common causes include:
A lower than normal levels may be due to:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
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, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.