Calcium Test

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At a Glance

Why Get Tested?

To determine if the concentration of calcium in your blood is at normal levels.

When to Get Tested?

In persons with kidney, bone, or nerve disease, or when symptoms of abnormal calcium are present.

Sample Required?

A blood sample taken from a vein in your arm; a timed urine collection may be used when blood calcium is abnormal; urine calcium measurements may also be requested if you have kidney stones

Test Preparation Needed?

Current practices do not require fasting or any other test preparation.

The Test Sample

What is being tested?

Calcium is one of the most important minerals in the body. About 99% of it is found in the bones, and most of the rest circulates in the blood. Roughly half of the calcium is referred to as 'free' (or 'ionized'), and is active within the body; the remaining half, referred to as 'bound' calcium, is attached to protein and other compounds and is inactive.

Most commonly, doctors measure the total amount of calcium in the blood (called total calcium); this measures both the active and inactive forms of calcium. If measurement of the active form of calcium (ionized calcium) is needed, special sample handling is required. Urine calcium tells how much calcium is being excreted by the kidneys.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm. A urine specimen may be required if your blood calcium is abnormal or if you have kidney stones, a timed collection is then preferred.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

Current practices do not require fasting or any other test preparation.

The Test

Common Questions

Ask a Laboratory Scientist

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.