Ammonia

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 important because ammonia is toxic (poisonous) to the brain. Very high ammonia levels, especially when they rise quickly (such as in newborns with urea cycle disorders, in Reye syndrome, or in sudden severe liver failure), can cause confusion, coma, and even permanent brain damage if not treated. In adults with long-standing liver disease, blood ammonia levels often go up and down without closely matching how a person feels, so the level alone does not predict how serious symptoms will be.

Liver disease is the most common cause of high ammonia levels. Other causes include kidney failure and genetic disorders called urea cycle disorders.

Your provider will use your test results, symptoms, and medical history to understand what your ammonia levels say about your health. Normal levels vary with age, but in general, low levels are normal and healthy.

If your test results are normal, your provider will order other tests to find out what's causing your symptoms.

If your test results show ammonia levels that are higher than normal, it usually means that your body is having trouble getting rid of ammonia. Many types of health conditions can cause high ammonia levels, including severe liver problems such as hepatic encephalopathy, cirrhosis, severe hepatitis, Reye's syndrome, and liver injury from medicines. Heart failure, advanced kidney problems, and severe lung disease such as emphysema can also raise ammonia. The level of ammonia in your blood doesn't always match how severe brain symptoms from liver disease are.

If the results of an ammonia levels test are high, more tests will usually be done to diagnose the cause. 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.