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Calcium (Ca) in Blood

(continued)

Results continued...

An ionized calcium test checks the amount of calcium that is not attached to protein in the blood. The level of ionized calcium in the blood is not affected by the amount of protein in the blood.

**Ionized calcium**
Adults:	4.65-5.28 mg/dL or 1.16-1.32 mmol/L
Children:	4.80-5.52 mg/dL or 1.20-1.38 mmol/L

High values

High values of calcium may be caused by:

Hyperparathyroidism.
Cancer, including cancer that has spread to the bones.
Tuberculosis.
Being on bed rest for a long time after a broken bone.
Paget's disease.

Low values

Low values of calcium may be caused by:

A low level of the blood protein albumin (hypoalbuminemia).
Hypoparathyroidism.
High levels of phosphate in the blood, which can be caused by kidney failure, laxative use, and other things.
Malnutrition caused by diseases such as celiac disease, pancreatitis, and alcoholism.
Osteomalacia.
Rickets.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking calcium or vitamin D in any form including milk, antacids, or supplements right before the test.
Taking medicines, such as diuretics. Many medicines can affect calcium levels in the blood.
Having dialysis.
Having a high volume blood transfusion or many blood transfusions in a short period of time.

What To Think About

More than one blood test may be needed to see if blood calcium levels are too high.
Low blood levels of calcium may be caused by low levels of protein (albumin) in the blood, because about half of all calcium in the blood is attached to albumin. For this reason, an ionized calcium level (which is not attached to albumin) and a blood albumin level may also be measured. For more information, see the topic Total Serum Protein.
Other tests that may be done to find the cause of abnormal blood calcium levels include blood tests for parathyroid hormone (PTH), chloride, acid phosphatase, alkaline phosphatase, and vitamin D. For more information, see the topics Parathyroid Hormone and Alkaline Phosphatase.
Calcium levels can also be checked in the urine. For more information, see the topic Calcium (Ca) in Urine.

Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

By	Healthwise Staff
Primary Medical Reviewer	E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer	Philip Belitsky, MD, FRCSC - Urology
Last Revised	September 20, 2010

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WebMD Medical Reference from Healthwise

Last Updated: September 20, 2010

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.