Top of the page
An ammonia test measures the amount of ammonia in the blood. Most ammonia in the body forms when protein is broken down by bacteria in the intestines. The liver normally converts ammonia into urea, which is then eliminated in urine.
Ammonia levels in the blood rise when the liver is not able to convert ammonia to urea. This may be caused by cirrhosis or severe hepatitis.
For this test, a blood sample may be taken from either a vein or an artery.
An ammonia test is done to:
Do not eat, drink anything other than water, or smoke for 8 hours before having an ammonia blood test. And avoid strenuous exercise just prior to having this test.
A health professional uses a needle to take a blood sample, usually from the arm.
A sample of blood from an artery is usually taken from the inside of the wrist (radial artery). But it can also be taken from an artery in the groin (femoral artery) or on the inside of the arm above the elbow crease (brachial artery).
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
Collecting blood from an artery is more painful than collecting it from a vein. That's because the arteries are deeper and are protected by nerves.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
There is little chance of a problem from having a blood sample taken from an artery.
Don't lift or carry objects for about 24 hours after you have had blood taken from an artery.
Results are usually available within 12 hours.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
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).
Adaptation Date: 2/24/2022
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
To learn more about Healthwise, visit Healthwise.org.
© 1995-2022 Healthwise, Incorporated. All rights reserved. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.