Phosphorus - blood

The serum phosphorus test measures the amount of phosphate in the blood.

How is the Test Performed?

A blood sample is needed. For information on how this is done, see: Venipuncture

Preparation for the Test

The health care provider may advise you to stop taking drugs that may affect the test.

How will the Test Feel?

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why is the Test Performed?

This test is performed to see how much phosphorus in your blood. Kidney, liver, and certain bone diseases can cause abnormal phosphorus levels.

Normal Results for Phosphorus - blood

Normal values range from 2.4 - 4.1 milligrams per deciliter (mg/dL).

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Higher than normal levels (hyperphosphatemia) may be due to many different health conditions. Common causes include:

Lower than normal levels (hypophosphatemia) may be due to:

Phosphorus - blood Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Considerations

The following can affect phosphorous levels:

  • Antacids
  • Enemas containing sodium phosphate
  • Excess vitamin D supplements
  • Glucose through a vein (intravenous)
  • Laxatives containing sodium phosphate

References

 

Yu SLA. Disorders of magnesium and phosphorous. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 121.

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Review Date: 11/17/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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