Ammonia Levels

An ammonia levels test measures the amount of ammonia in a sample of your blood. Ammonia is also called NH3. It is a normal waste product in your body.

Healthy bacteria in your intestines make ammonia when you digest protein in the foods you eat. Normally, your liver changes ammonia into another waste product called urea. Your kidneys get rid of urea in urine (pee).

This process is called the urea cycle. When you're healthy, the urea cycle prevents ammonia from building up in your blood. This is very important because ammonia is toxic (poisonous) to your brain.

Even small increases in the level of ammonia in your blood can cause permanent brain damage, coma, and even death. Liver disease is the most common cause of high ammonia levels. Other causes include kidney failure and genetic disorders called urea cycle disorders.

The medical term for high ammonia levels is hyperammonemia.

Why this test is done

You may need this test if you have symptoms that could be from too much ammonia in your blood. The symptoms depend on how high your ammonia levels are and your age. 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 and/or making grunting sounds when breathing. If your baby or child has any symptoms of high ammonia levels, contact their provider right away.

If you have a family history of genetic urea cycle disorders, you or your child may need this test even if you don't have symptoms.

If you've been diagnosed with high ammonia levels, you may need this test to see how well your treatment is working.

How to prepare

Your provider will give you specific instructions about how to prepare for an ammonia levels test. You should not smoke for several hours before the test. You may be asked to avoid strenuous exercise and alcohol for a period of time.

You may also need to fast (not eat or drink) for several hours. Your provider may tell you to stop taking certain medicines, including diuretics (water pills) and opioid pain medicines. But never stop taking any prescription medicines without talking with your provider first.

Babies do not need any special preparations before the test.

Sample type

Blood Urine

Other names for this test

NH3 test, blood ammonia test, serum ammonia, ammonia; plasma