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Ammonia blood test

Serum ammonia; Encephalopathy - ammonia; Cirrhosis - ammonia; Liver failure - ammonia

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Definition

The ammonia test measures the level of ammonia in a blood sample.

How the Test is Performed

A blood sample is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

How to Prepare for the Test

Your health care provider may ask you to stop taking certain drugs that may affect test results. These include:

  • Alcohol
  • Acetazolomide
  • Narcotics
  • Valproic acid

You should not smoke before your blood is drawn.

Normal Results

The normal range is 15 to 45 µ/dL (11 to 32 µmol/L).

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.

Risks

Veins and arteries vary in size from one person 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)

What Abnormal Results Mean

Abnormal results may mean you have increased ammonia levels in your blood. This may be due to any of the following:

A high-protein diet can also raise the blood ammonia level.

Why the Test is Performed

Ammonia (NH3) is produced by cells throughout the body, especially the intestines, liver, and kidneys. Most of the ammonia produced in the body is used by the liver to produce urea. Urea is also a waste product, but it is much less toxic than ammonia. Ammonia is especially toxic to the brain. It can cause confusion, low energy, and sometimes coma.

This test may be done if you have, or your provider thinks you have, a condition that may cause a toxic buildup of ammonia. It is most commonly used to diagnose and monitor hepatic encephalopathy, a severe liver disease.

Review Date: 2/13/2017
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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