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Phosphorus - blood

Definition

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

Alternative Names

Phosphorus - serum; HPO4, PO4; Inorganic phosphate; Phosphorus blood test; Serum phosphorus

How the test is performed

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

How to prepare for the test

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

How the test will 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 the test is 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 Values

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:

What the risks are

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)

Special 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. . 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 121.

Encyclopedia content is provided as information only and not intended to replace the advice and instruction from your personal physician.