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Ammonium ion

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Definition:

Ammonium ion test measures the amount of ammonium ions in a blood sample.

Alternative Names:

NH4+ test

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test:

Fast for 8 - 12 hours. The health care provider may advise you to withhold drugs that may affect test results.

Drugs that can interfere with the test include thiazide or loop diuretics, barbiturates, acetazolamide, neomycin, and oral kanamycin. Consult the health care provider before this test if you are taking any of these medications.

How the test will feel:

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

Why the test is performed:

This test may be performed when a condition that may cause toxic accumulation of ammonia is present or suspected.

Ammonia (NH4+) is produced by cells throughout the body, especially the intestines, liver, and kidneys. In the kidneys, ammonia plays a minor role in the acid/base balance, but is otherwise a metabolic waste product (primarily the result of protein metabolism ).

Most of the ammonia produced in the body is used by the liver in the production of urea. Urea is also a waste product but is much less toxic than ammonia.

Ammonia is especially toxic to the brain and can cause confusion, lethargy, and sometimes coma.

• Review Date: 1/17/2007
• Reviewed By: Frank A. Greco, M.D., Ph.D., Director, Biophysical Laboratory, The Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network.

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