Phosphate in Blood

A phosphate in blood test measures the amount of phosphate in a sample of your blood. Phosphate contains the mineral phosphorus. So, a phosphate test is sometimes called a phosphorus test.

Phosphate is a type of electrolyte. Electrolytes are electrically charged minerals. They help control the amount of fluid and the balance of acids and bases (pH balance) in your body.

Your body also needs phosphates for many other important processes, such as: Building strong bones and teeth. Most of the phosphate in your body is found in your bones where it is combined with the mineral calcium.; Making energy.; Helping your nerves and muscles work properly.; The phosphorus in phosphate comes from the foods you eat, including nuts and seeds, dairy products, dried beans, meats, poultry, and eggs. Your body tightly controls the amount of phosphate in your blood mainly through your: Kidneys.

They filter extra phosphate from your blood and get rid of it through urine (pee). If your phosphate level is low, your kidneys limit the amount lost through urine.; Intestines. They control how much phosphorous you absorb from the foods you eat.; The amount of phosphate in your blood is also linked to your levels of: Calcium.

When blood calcium levels increase, phosphate levels decrease. And when calcium levels decrease, phosphate levels increase.; Vitamin D. It helps your body use phosphate.; Parathyroid hormone (PTH).

This hormone is made by parathyroid glands in your neck. It helps balance phosphate and calcium levels in your blood.; Abnormal phosphate levels may be a sign of problems with the systems in your body that control phosphate levels. To help understand the cause of abnormal levels, the test is often done with blood tests that measure calcium, vitamin D, and PTH.

Why this test is done

Phosphate levels that are either high or mildly low usually don't cause any symptoms on their own. But you may need a phosphate test with other tests if you:

• Have had an abnormal result on a calcium blood test. A calcium test may be part of a routine exam. Abnormal levels are often linked to abnormal phosphate levels.
• Have symptoms of low calcium levels. High levels of phosphate can lower calcium levels in your blood, which can cause symptoms, such as:
• Nails that break easily, and/or hair that becomes coarse
• Rash and/or itchy skin
• Muscle cramps
• Bone pain
• Seizures
• Irregular heartbeat (arrhythmia)
• Have symptoms of severely low phosphate levels. This condition can become life-threatening and needs immediate treatment. Symptoms may include:
• Muscle pain and/or weakness
• Bone pain
• Changes in your mental condition, such as feeling confused or very irritable
• Seizures
• Coma

You may also need to have your phosphate levels checked if you have or may have a condition that can cause abnormal phosphate levels, such as:

• Kidney disease
• Malnutrition
• Malabsorption syndrome
• A parathyroid gland disorder
• Using certain medicines

How to prepare

Your health care provider will tell you how to prepare for your test. You may need to fast (not eat or drink) for several hours before you give your blood sample.

Certain medicines, vitamins and supplements can affect the accuracy of your test results. So tell your provider about everything you take, including over-the-counter medicines. But don't stop taking any prescription medicines unless your provider tells you to.

Sample type

Blood

Other names for this test

phosphorus test, PO4, phosphorus-serum, phosphate, inorganic phosphorus