Phosphate in Blood
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.
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
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. A hormone called parathyroid hormone (PTH) regulates the levels of calcium and phosphorus in your blood. When the phosphorus level is measured, a vitamin D level, and sometimes a PTH level, is measured at the same time. Vitamin D is needed for your body to take in phosphate.
The 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.
Why It Is Done
A test to measure phosphate in blood may be done to:
- Check phosphate levels if you have kidney
disease or bone disease.
- Help find problems with certain glands,
such as the
- Find a reason for abnormal vitamin D levels.
How To Prepare
Many medicines can change the results of this test. Be sure to tell
your doctor about all the nonprescription and prescription medicines you
take, including vitamin D supplements.
Talk to your doctor about any concerns you have regarding the need
for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).