This test measures the amount of potassium that is in the blood or serum. Potassium is one of the main minerals called electrolytes that are found in the blood and in all of the cells of the body.

Who is a candidate for the test?

If a doctor suspects one of the conditions that results from too high or too low a level of potassium, he or she may order this test.

How is the test performed?

In order to measure the amount of potassium 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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.