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.
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:
- Eating a high-protein or a low-protein diet.
- Using medicines that increase blood ammonia levels, such as acetazolamide, valproate, and some diuretics (such as furosemide).
- Using medicines that decrease ammonia levels, such as diphenhydramine, isocarboxazid, lactulose, neomycin, phenelzine, tetracycline, and tranylcypromine.
- Strenuous exercise just before the test.
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 .
- 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.