Ionized Calcium Test

Definition

Ionized calcium is a test that measures the amount of free calcium (Ca++, Ca +2) in the blood. (See also serum calcium.) Ionized or free calcium is the metabolically-active portion of calcium and is not bound to proteins in the blood.

Blood test

Alternative Names

How the test is performed

Blood is drawn from a vein (venipuncture) or capillary. The laboratory centrifuges the blood to separate the cells from the serum. The ionized calcium test is done on serum.

How to prepare for the test

Fast for at least 6 hours before the test. Your medical provider may instruct you to withhold drugs that can affect the test.

Drugs that can increase ionized calcium measurements include calcium salts (found in nutritional supplements or antacids), hydralazine, lithium, thiazide diuretics, and thyroxine.

Normal Values

• Children: 4.4 - 6.0 mg/dl
• Adult: 4.4 - 5.3 mg/dl

Note: mg/dl = milligrams per deciliter

Normal values may vary slightly from laboratory to laboratory.

What abnormal results mean

Greater-than-normal levels may indicate:

• Hyperparathyroidism
• Metastatic bone tumor
• Milk-alkali syndrome
• Multiple myeloma
• Paget's disease
• Sarcoidosis
• tumors producing a PTH-like substance
• Vitamin D intoxication

• Hypoparathyroidism
• Malabsorption
• Osteomalacia
• Pancreatitis
• Renal failure
• Rickets
• Vitamin D deficiency

Special considerations

An excess ingestion of milk or vitamin D as a dietary supplement can increase calcium levels.

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Review Date:6/13/2005
Reviewed By: Debbie Cohen, M.D., Renal and Electrolyte Division, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.