What is an ammonia levels test?

This test measures the level of ammonia in your blood. Ammonia, also known as NH3, is a waste product made by your body during the digestion of protein. Normally, ammonia is processed in the liver, where it is changed into another waste product called urea. Urea is passed through the body in urine.

If your body can't process or eliminate ammonia, it builds up in the bloodstream. High ammonia levels in the blood can lead to serious health problems, including brain damage, coma, and even death.

High ammonia levels in the blood are most often caused by liver disease. Other causes include kidney failure and genetic disorders.

Other names: NH3 test, blood ammonia test, serum ammonia, ammonia; plasma

What is it used for?

An ammonia levels test may be used to diagnose and/or monitor conditions that cause high ammonia levels. These include:

• Hepatic encephalopathy, a condition that happens when the liver is too diseased or damaged to properly process ammonia. In this disorder, ammonia builds up in the blood and travels to the brain. It can cause confusion, disorientation, and coma. It can sometimes be fatal.
• Reye syndrome, a serious and sometimes fatal condition that causes damage to the liver and brain. It mostly affects children and teenagers who are recovering from viral infections such as chickenpox or the flu and have taken aspirin to treat their illnesses. The cause of Reye syndrome is unknown. But because of the risk, children and teens should not take aspirin unless specifically recommended by their health care provider.
• Urea cycle disorders, rare genetic defects that affect the body's ability to change ammonia into urea.

The test may also be used to monitor the effectiveness of treatment for liver disease or kidney failure.

Why do I need an ammonia levels test?

You may need this test if you have liver disease and are showing symptoms of a brain disorder. Symptoms include:

• Confusion
• Excessive sleepiness
• Disorientation, the condition of being confused about time, place, and/or your surroundings
• Mood swings
• Hand tremors

Your child may need this test if he or she has symptoms of Reye syndrome. These include:

• Vomiting
• Sleepiness
• Irritability
• Seizures

Your newborn baby may need this test if he or she has any of the above symptoms. The same symptoms may be a sign of a urea cycle disorder.

What happens during an ammonia levels test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

To test a newborn, a health care provider will clean your baby's heel with alcohol and poke the heel with a small needle. The provider will collect a few drops of blood and put a bandage on the site.

Will I need to do anything to prepare for the test?

You should not exercise or smoke cigarettes for about eight hours before an ammonia test.
Babies do not need any special preparations before the test.

Are there any risks to the test?

There is very little risk to having a blood test. You or your child may have slight pain or bruise at the spot where the needle was put in, but most symptoms go away quickly.