Calcium

Alternate Names
serum calcium
total calcium
Ca++

Definition of Calcium

This test measures the amount of calcium in the blood or serum. Calcium is one of the important electrolytes or minerals that is found in the body. Ninety-nine percent of all of the calcium that is found in the body is in the bone. The remaining 1% of the calcium helps the body work. Calcium is needed for the proper functioning of the nerve, heart, and skeletal muscle cells. The right amount of calcium is also vital for the control of hormones. In addition, it helps chemicals called neurotransmitters to send nerve impulses through the body.

Who is a candidate for the test?

This test is ordered to help in the diagnosis of any of several different conditions directly linked with calcium imbalances, such as those involving the parathyroid glands. Calcium is also checked when certain other conditions have been diagnosed that may indirectly affect the level of calcium in the body. These may include kidney disease, cancer, or sarcoidosis.

How is the test performed?

In order to measure the amount of calcium in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube called a tourniquet is tied around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them.

A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

What is involved in preparation for the test?

No preparation is generally needed for this test.

What do the test results mean?

Normal values for the total amount of calcium in the blood range from 8.6-10.0 milligrams per deciliter (mg/dL).

Abnormally high levels of calcium can be seen in the following instances:

• certain cancers
• use of diuretics
• hyperparathyroidism
• kidney disorders
• dehydration
• high protein levels in the blood

Abnormally low levels may be a sign of:

• low protein in the blood
• hypoparathyroidism
• kidney disease
• vitamin D deficiency
• alcoholism
• pancreatitis
• reactions to certain medicines