Also known as: Free calcium and Ionized calcium
- Your health care provider will tell you if you need to stop taking any medicines before you have this test.
- Do not stop or change your medications without talking to your doctor first.
- Children: 4.4 - 6.0 milligrams per deciliter (mg/dL)
- Adults: 4.4 - 5.3 mg/dL
- Decreased levels of calcium in the urine from an unknown cause
- Milk-alkali syndrome
- Multiple myeloma
- Paget's disease
- Thiazide diuretics
- Thrombocytosis (high platelet count)
- Vitamin A excess
- Vitamin D excess
Ionized calcium is calcium in your blood that is not attached to proteins. It is also called free calcium.
All cells need calcium in order to work. Calcium helps build strong bones and teeth. It is important for heart function. It also helps with muscle contraction, nerve signaling, and blood clotting.
This article discusses the test used to measure the amount of ionized calcium in blood.
How the test is performed
A blood sample is needed. Most of the time blood is drawn from a vein located on the inside of the elbow or the back of the hand.
How to prepare for the test
You should not eat or drink for at least 6 hours before the test.
Many medicines can interfere with blood test results.
Why the test is performed
Your doctor may order this test if you have signs of kidney or parathyroid disease. The test may also be done to monitor progress and treatment of these diseases.
Most of the time, blood tests measure your total calcium level. This looks at both ionized calcium and calcium attached to proteins. You may need to have a separate ionized calcium test if you have factors that increase or decrease total calcium levels. These may include abnormal blood levels of albumin or immunoglobulins.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What abnormal results mean
Higher-than-normal levels of ionized calcium may be due to:
Lower-than-normal levels may be due to:
Wysolmerski JJ, Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 253.
- Review date:
- May 5, 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 A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.
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. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.