Phosphate in Blood

Blood Phosphate (PO4), PO4 (Phosphate), Blood

Test Overview

A phosphate test measures the amount of phosphate in a blood sample. Phosphate is a charged particle (ion) that contains the mineral phosphorus. The body needs phosphorus to build and repair bones and teeth, help nerves function, and make muscles contract. Most (about 85%) of the phosphorus contained in phosphate is found in bones. The rest of it is stored in tissues throughout the body.

The kidneys help control the amount of phosphate in the blood. Extra phosphate is filtered by the kidneys and passes out of the body in the urine. A high level of phosphate in the blood is usually caused by a kidney problem.

The amount of phosphate in the blood affects the level of calcium in the blood. Calcium and phosphate in the body react in opposite ways: As blood calcium levels rise, phosphate levels fall. But this relation between calcium and phosphate may be disrupted by some diseases or infections. For this reason, phosphate and calcium levels are usually measured at the same time.

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Author:	Maria G. Essig, MS, ELS Ralph Poore	Last Updated: January 29, 2008
Medical Review:	Anne C. Poinier, MD - Internal Medicine Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
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