Calcium

Also known as: Total calcium; Ionized calcium

Formal name: Calcium

The Test Sample

What is being tested?

Calcium is one of the most important minerals in your body. It is essential for the proper functioning of muscles, nerves, and the heart and is required in blood clotting and in formation of bones. About 99% of calcium is found in the bones while the remainder circulates in the blood. Roughly half of the calcium in the blood is "free" and is metabolically active. The remaining half is "bound" calcium. It is attached to albumin and other compounds and is metabolically inactive.

There are two tests to measure blood calcium. The total calcium test measures both the free and bound forms. The ionized calcium test measures only the free, metabolically active form.

Some calcium is lost from your body every day, filtered from the blood by the kidneys and excreted into the urine. Measurement of the amount of calcium in the urine is used to determine how much calcium is being eliminated by the kidneys.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm. If a urine collection is required, a timed collection is best.

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?

No special preparation is needed for this test.