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An ammonia test measures the amount of ammonia in the blood. Results are usually available within 12 hours.


The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Ammonia 1


9.5-49 micrograms per deciliter (mcg/dL)

7-35 micromoles per liter (mcmol/L)


40-80 mcg/dL

28-57 mcmol/L


90-150 mcg/dL

64-107 mcmol/L

High values

High levels of ammonia in the blood may be caused by:

High ammonia values in a baby may be present when the blood types of a mother and her baby do not match (hemolytic disease of the newborn).

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

What To Think About

  • Ammonia levels do not always reflect the severity of a person's symptoms. For example, a person with severe cirrhosis may have only slightly elevated blood ammonia levels and yet may not be thinking clearly or may be sleepy or in a coma. Other people with very high ammonia levels may think and act normally.
  • Symptoms of a high ammonia level, such as confusion or extreme sleepiness, may be treated with a medicine called lactulose, a laxative that works by reducing ammonia production in the intestines camera.gif.
  • It is common for newborns to have slightly high levels of ammonia in their blood. But the levels are temporary and usually do not cause symptoms.

WebMD Medical Reference from Healthwise

Last Updated: /2, 14 1
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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