Serum Phosphorus

Alternate Names : Phosphorus, PO4

Serum phosphorus measures the amount of phosphorus in the blood or serum. Phosphorus is a mineral that is found in all cells in the body. It is also found in proteins and enzymes. Phosphorus is obtained through the digestion of food in the small intestine. Most of the phosphorus is then removed from the blood by the kidneys.

Who is a candidate for the test?

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

How is the test performed?

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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.