Calcium blood test

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 half of the calcium in the blood is attached to proteins, mainly albumin. For this reason, the calcium blood test can be misleading, and sometimes needs tests to confirm the result.

A separate test measures calcium that is not attached to proteins in your blood. Such calcium is called free or ionized calcium.

Calcium can also be measured in the urine.

A blood sample is needed.

The health care provider may tell you to temporarily stop taking certain medicines that can affect the test. Medicines include:

  • Calcium salts (may be found in nutritional supplements or antacids)
  • Lithium
  • Thiazide diuretics
  • Thyroxine
  • Vitamin D

Drinking too much milk (two or more quarts a day or having an equivalent 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 sensation. Afterward, there may be some throbbing or slight bruising. These soon go 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:

  • Certain bone diseases
  • Certain cancers, such as multiple myeloma, a cancer of the breast, lung, neck, and kidney
  • Chronic kidney disease
  • Chronic liver disease  
  • Disorders of the parathyroid gland
  • Disorders that affect how your intestines absorb nutrients
  • Overactive thyroid gland or taking too much thyroid hormone medication

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.

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.

Higher than normal levels may be due to a number of health conditions. Common causes include:

Lower than normal levels may be due to:

  • Disorders that affect absorption of nutrients from the intestines
  • Hypoparathyroidism
  • Kidney failure
  • Low blood level of albumin
  • Liver disease
  • Magnesium deficiency
  • Osteomalacia
  • Pancreatitis
  • Vitamin D deficiency

Calcium blood test Risks

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient 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:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)
  • Multiple punctures to locate veins

References

Pincus MR, Abraham NZ Jr. Interpreting laboratory results. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 8.

Wysolmerski JJ, Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 253.

Review Date: 10/29/2013
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, Bethanne Black, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2014 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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