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 healthcare 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 healthcare provider will probably test your calcium level as well. Additional tests depend on which condition your healthcare provider suspects.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
Results of this test are given in milligrams per deciliter (mg/dL). A normal phosphorus reading is between 2.7 and 4.6 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?
Phosphorus levels can be affected by what you eat and drink, including:
Many types of beans
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 healthcare provider for specific instructions. Be sure your healthcare 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.
December 16, 2017
Causes of hypophosphatemia. UpToDate., Disorders of calcium, magnesium, and phosphate balance. Brenner and Rector's The Kidney. Taal MW. 2012, 9th ed., pp. 689-725., Evaluation and treatment of hypophosphatemia. UpToDate, Overview of the causes and treatment of hyperphosphatemia. UpToDate, Phosphate (serum). Ferri's Best Test: A practical guide to laboratory medicine and diagnostic imaging. Ferri FF. 2015, 3rd ed., pp. 103-90.
Freeborn, Donna, PhD, CNM, FNP,Haldeman-Englert, Chad, MD