Phosphorus

Does this test have other names?

Phosphorus blood test, phosphate test

What is this test?

This test measures the level of phosphorus in your blood. Phosphorus is a common mineral found in the food you eat. It's also found in teeth and bones.

Having a high or low level of phosphorus in your bloodstream can signal a number of health conditions. Most commonly, a high level of phosphorus is related to a kidney disorder. It shows that your kidneys are having difficulty clearing phosphorus from your blood. A high level of phosphorus can also mean uncontrolled diabetes and other endocrine disorders.

Why do I need this test?

You may need this test if your health care provider suspects that you have a kidney disorder. You may also need this test if you are having trouble controlling your diabetes. You may need this test if you have symptoms of kidney disease, including bone problems, fatigue, and weakness, but you may not have any symptoms at all.

What other tests might I have along with this test?

Phosphorus levels are closely related to calcium levels, so your health care provider will probably test your calcium level as well. Additional tests depend on which condition your provider suspects.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your provider what your test results mean for you.

Results of this test are given in milligrams per deciliter (mg/dL). A normal phosphorus is between 3 and 4.5 mg/dL, but normal ranges may vary. A number that is either higher or lower than that could mean a possible kidney problem.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Certain foods and drinks that are high in phosphorus can affect your test results. Talk with your health care provider about your diet and how it might affect your test results. A few examples of high phosphorus foods and drinks include:

• Chocolate.

• Cheese.

• Fish.

• Many types of beans.

• Beer.

• Cola.

Some medicines and medical procedures, such as dialysis, can also affect phosphorus levels.

How do I get ready for this test?

You may need to fast starting at midnight before the test. Ask your health care provider for specific directions. Be sure your provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.