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Phosphate in Urine

What is a phosphate in urine test?

A phosphate in urine test measures the amount of phosphate in your urine. Phosphate is an electrically charged particle that contains the mineral phosphorous. Phosphorous works together with the mineral calcium to build strong bones and teeth. It also plays an essential role in nerve function and how the body uses energy.

Your kidneys control the amount of phosphate in your body. If you have a problem with your kidneys, it can affect your phosphate levels. Phosphate levels that are too low or too high can be a sign of a serious health problem.

Other names: phosphorous test, P, PO4

What is it used for?

A phosphate in urine test may be used to:

  • Help diagnose kidney problems
  • Find the cause of a kidney stone, a small, pebble-like substance that can form in the kidneys
  • Diagnose disorders of the endocrine system. The endocrine system is a group of glands that release hormones into your body. Hormones are chemical substances that control many important functions, including growth, sleep, and how your body uses food for energy.

Why do I need a phosphate in urine test?

Most people with high phosphate levels don't have any symptoms.

You may need a phosphate in urine test if you have symptoms of a low phosphate level. These include:

  • Fatigue
  • Muscle cramping
  • Loss of appetite
  • Joint pain

You may also need a phosphate in urine test if you've had abnormal results on a calcium test. Calcium and phosphate work together, so problems with calcium levels can mean problems with phosphate levels as well. Calcium testing in blood and/or urine is often part of a routine checkup.

What happens during a phosphate in urine test?

You'll need to collect all your urine during a 24-hour period. This is called a 24-hour urine sample test. Your health care provider or a laboratory professional will give you a container to collect your urine in and instructions on how to collect and store your samples. A 24-hour urine sample test generally includes the following steps:

  • Empty your bladder in the morning and flush that urine down. Do not collect this urine. Record the time.
  • For the next 24 hours, save all your urine in the container provided.
  • Store your urine container in a refrigerator or a cooler with ice.
  • Return the sample container to your health provider's office or the laboratory as instructed.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a phosphate in urine test. Be sure to carefully follow all the instructions for providing a 24-hour urine sample.

Are there any risks to the test?

There is no known risk to having a phosphate in urine test.

What do the results mean?

The terms phosphate and phosphorous can mean the same thing in test results. So your results may show phosphorous levels rather than phosphate levels.

If your test shows you have high phosphate/phosphorous levels, it may mean you have:

  • Kidney disease
  • Too much vitamin D in your body
  • Hyperparathyroidism, a condition in which your parathyroid gland produces too much parathyroid hormone. The parathyroid gland is a small gland in your neck that helps control the amount of calcium in your blood.

If your test shows you have low phosphate/phosphorous levels, it may mean you have:

  • Kidney disease
  • Liver disease
  • Malnutrition
  • Alcoholism
  • Diabetic ketoacidosis
  • Osteomalacia (also known as rickets), a condition that causes bones to become soft and deformed. It's caused by a vitamin D deficiency.

If your phosphate/phosphorous levels are not normal, it doesn't necessarily mean you have a medical condition needing treatment. Other factors, such as your diet, can affect your results. Also, children often have higher phosphate levels because their bones are still growing. If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about a phosphate in urine test?

Phosphate is sometimes tested in the blood instead of urine.

References

  1. Hinkle J, Cheever K. Brunner & Suddarth’s Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Calcium, Serum; Calcium and Phosphates, Urine; 118–9 p.
  2. Johns Hopkins Medicine [Internet]. Johns Hopkins Medicine; Health Library: Kidney Stones [cited 2018 Jan 19]; [about 3 screens]. Available from:
  3. Lab Tests Online [Internet]. Washington D.C.; American Association for Clinical Chemistry; c2001–2018. Glossary: 24-Hour Urine Sample [updated 2017 Jul 10; cited 2018 Jan 19]; [about 3 screens]. Available from:
  4. Lab Tests Online [Internet]. Washington D.C.; American Association for Clinical Chemistry; c2001–2018. Glossary: Hyperparathyroidism [updated 2017 Jul 10; cited 2018 Jan 19]; [about 3 screens]. Available from:
  5. Lab Tests Online [Internet]. Washington D.C.; American Association for Clinical Chemistry; c2001–2018. Glossary: Hypoparathyroidism [updated 2017 Jul 10; cited 2018 Jan 19]; [about 3 screens]. Available from:
  6. Lab Tests Online [Internet]. Washington D.C.; American Association for Clinical Chemistry; c2001–2018. Parathyroid Diseases [updated 2017 Oct 10; cited 2018 Jan 19]; [about 3 screens]. Available from:
  7. Lab Tests Online [Internet]. Washington D.C.; American Association for Clinical Chemistry; c2001–2018. Phosphorous [updated 2018 Jan 15; cited 2018 Jan 19]; [about 3 screens]. Available from:
  8. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2018. Overview of Phosphate’s Role in the Body [cited 2018 Jan 19]; [about 2 screens]. Available from:
  9. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: endocrine system [cited 2018 Jan 19]; [about 3 screens]. Available from:
  10. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: osteomalacia [cited 2018 Jan 19]; [about 3 screens]. Available from:
  11. National Kidney Foundation [Internet]. New York: National Kidney Foundation Inc., c2017. A to Z Health Guide: Phosphorous and Your CKD Diet [cited 2018 Jan 19]; [about 3 screens]. Available from:
  12. University of Maryland Medical Center [Internet]. Baltimore: University of Maryland Medical Center; c2018. Phosphorous [cited 2018 Jan 19]; [about 5 screens]. Available from:
  13. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2018. Health Encyclopedia: Kidney Stone (Urine) [cited 2018 Jan 19]; [about 2 screens]. Available from:
  14. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. Phosphate in Urine: How It is Done [updated 2017 May 3; cited 2018 Jan 19]; [about 4 screens]. Available from:
  15. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. Phosphate in Urine: Results [updated 2017 May 3; cited 2018 Jan 19]; [about 8 screens]. Available from:
  16. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. Phosphate in Urine: Test Overview [updated 2017 May 3; cited 2018 Jan 19]; [about 2 screens]. Available from:
  17. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. Phosphate in Urine: What To Think About [updated 2017 May 3; cited 2018 Jan 19]; [about 10 screens]. Available from:
  18. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2018. Phosphate in Urine: Why It is Done [updated 2017 May 3; cited 2018 Jan 19]; [about 3 screens]. Available from:

The medical information provided is for informational purposes only, and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.

In the event of a medical emergency, call 911 immediately.