Ammonia Levels

What is an ammonia levels test?

An ammonia levels test measures the amount of ammonia (also called NH3) in a sample of your blood. Ammonia is a normal waste product in your body made by healthy bacteria in your intestines whenever they help you digest proteins in the foods you eat.

High levels of ammonia (also called hyperammonemia) in your blood can cause serious health problems. This is because ammonia is toxic (poisonous) to your brain. Even small increases in the level of ammonia in your blood can cause brain damage. If levels stay high for too long, it can even lead to death.

The most common cause of hyperammonemia is liver disease. This can include cirrhosis, hepatitis, or liver failure. Your liver processes ammonia. Liver diseases damage your liver's ability to do this job. So, if you have liver disease, especially if it's severe, you may have higher ammonia levels. Your levels can also go up if you have liver disease and experience something called a “triggering event.” These are events that can suddenly worsen your liver's health and include:

• An infection
• Bleeding in the digestive system
• Dehydration

Other causes of high ammonia levels include kidney failure or kidney disease and genetic disorders called urea cycle disorders.

If you have a urea cycle disorder, you lack enzymes in your liver that change ammonia into another waste product called urea. Enzymes are proteins that speed up certain chemical reactions in your body. The process of turning ammonia into urea is called the urea cycle. Once the enzymes in your liver turn ammonia into urea, your kidneys can get rid of it in your urine (pee).

Without these enzymes in your liver to turn ammonia into urea, ammonia will build up in your blood.

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

What is an ammonia levels test used for?

An ammonia levels test checks how well your body can get rid of ammonia. The results can then be used to help diagnose hyperammonemia (high ammonia levels) in people who have symptoms. They can also help a health care provider diagnose conditions that could be causing hyperammonemia. These include:

• Hepatic encephalopathy. This condition happens when toxins, including ammonia, build up in your brain because your liver is unable to break them down. It can cause memory loss, confusion, loss of consciousness, and coma.
• Reye syndrome. This rare disease damages the brain and liver. Without treatment, it causes death. It mostly happens in children younger than 15 who have had a viral infection that causes a fever, such as chickenpox or the flu. Taking aspirin during a viral illness may increase the risk of Reye syndrome.
• Urea cycle disorders (UCDs). This is a group of rare genetic conditions that you inherit from your parents. If you have a UCD, you lack the enzymes that help change ammonia into urea. Symptoms may show up shortly after birth or later in life. Newborns are tested for certain UCDs as part of routine newborn screening. Your child's provider can explain more about which UCD screening tests are used in your state.

Ammonia levels tests alone can't diagnose conditions that increase the amount of ammonia in your blood. But they may be used with other tests to help find the cause.

These tests can also help a provider monitor treatment for conditions that cause high ammonia levels, such as liver failure and hepatic encephalopathy.

Why do I need an ammonia levels test?

You may need this test if you have:

• Symptoms that could be from too much ammonia in your blood
• A family history of genetic urea cycle disorders (even if you don't have symptoms)
• Been diagnosed with high ammonia levels, and your provider wants to see how well your treatment is working

The symptoms of hyperammonemia (high ammonia levels) depend on your age and how high your ammonia levels are. Symptoms in children and adults may include:

• Feeling irritable
• Lack of energy and mental alertness or being very sleepy
• Vomiting
• Headache
• Loss of muscle coordination that may cause difficulties with walking or speech
• Changes in behavior
• Confusion, including not being sure about the time and/or where or who you are
• Mood swings
• Seizures

Other symptoms in children may include:

• Not growing taller or gaining weight as expected
• Lack of muscle tone (limp muscles)
• Developmental delays in children or infants

Newborn babies may develop symptoms of high ammonia levels within three days after birth. Symptoms in newborns include the above symptoms and may also include fast breathing or grunting while breathing.

If you or your baby or child has any symptoms of high ammonia levels, call 911 or go to your local emergency room.

What happens during an ammonia levels test?

In most cases, 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.

In certain cases, the blood sample may be taken from an artery, which is a blood vessel that carries blood from your heart to the rest of your body. Some providers think blood from an artery may provide more accurate results. The blood is taken from an artery in your wrist, arm, or groin using a needle attached to a syringe.

Taking blood from an artery tends to be more uncomfortable than blood tests that use a vein. So, numbing medicine may be applied to your skin first. Afterwards, the site will be bandaged, and pressure will be applied for at least five minutes to stop bleeding. You may be told to avoid lifting heavy objects for 24 hours after the test.

To get a blood sample from a newborn, a provider will clean the baby's heel with alcohol. Then the provider will stick the baby's heel with a small needle to collect a few drops of blood. The heel will then be bandaged.

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

Your provider will give you specific instructions about how to prepare for an ammonia levels test. You may be asked to:

• Not smoke for several hours before the test.
• Avoid strenuous exercise and alcohol.
• Fast (not eat or drink) for several hours.
• Stop taking certain medicines, including diuretics (water pills) and opioid pain medicines. However, you should never stop taking any prescription medicines without talking with your provider first.

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 may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

If your blood sample was taken from an artery, you may also have some bleeding where the needle was put in. Very rarely, the needle may damage a nerve or the artery.

There is also very little risk to your baby having a heel stick test. Your baby may feel a little pinch when the heel is poked, and a small bruise may form at the site.

What do the results mean?

Your provider will use your test results, symptoms, and medical history to understand what your ammonia levels say about your health.

If your test results are within or below a healthy range, your provider will order other tests to find out what's causing your symptoms. Healthy levels vary with age, and in general low levels aren't a sign of any health problems.

If your test results show ammonia levels that are above a healthy range, it usually means that your body or your child's body is having trouble getting rid of ammonia. This can mean you or your child have a condition, such as liver disease or hepatic encephalopathy, that can cause high ammonia levels. It may also mean certain medicines are causing the problem. A provider will usually order other tests to make a diagnosis.

If you or your child has a condition that causes high ammonia levels, treatment will depend on the condition that's causing the problem. If you have questions about your test results or treatment, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.