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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). You will be seated with your arm extended and your wrist resting on a small pillow. The health professional drawing the blood may rotate your hand back and forth and feel for a pulse in your wrist.
To prevent the chance of damaging the artery of the wrist when the blood sample is taken, a procedure called the Allen test may be done to make sure that blood flow to your hand is normal. An ammonia test will not be done on an arm used for dialysis or if there is an infection or inflammation in the area of the puncture site.
The health professional taking a sample of your blood will:
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.
Though problems are rare, be careful with the arm or leg that had the blood taken. Do not 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: 11/16/2021
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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