Preparation and Procedure
Preparation may be necessary for some patients. Certain drugs may increase the level of calcium in the blood, therefore, may need to be temporarily discontinued before having this test. These may include calcium salts, thiazide diuretics, vitamin D, lithium, and thyroxine. Consuming more than two quarts or milk everyday may also increase blood-calcium levels.
The serum calcium blood test is done by drawing blood from a vein. This involves gently inserting a needle into one of the patient's veins and then allowing the blood to collect into a vial. A tourniquet will be tied around the arm a few inches above the intended puncture site. The health care provider will feel for a vein and then gently insert the needle. Once enough blood is collected, the tourniquet is untied and removed, the needle is removed, and a small bandage is placed over the puncture site. Some slight bruising or soreness may occur after this is done.
Infants and young children will typically have their blood drawn using a lancet. The lancet will puncture the skin and then the blood will collect onto a test strip or slide, or into a pipette.
How the test feels will vary among patients. Patients have reported a slight prick to moderate pain. For most patients any discomfort experienced is tolerable.