High Ammonia Levels: Symptoms, Causes, Treatment

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Ammonia is a toxic waste product produced by bacteria in the intestines during protein digestion. Under normal circumstances, ammonia is processed in the liver, where it is turned into a less toxic chemical called urea and eliminated through the urine.

When a person cannot process ammonia, it can build up in the bloodstream. High ammonia levels (hyperammonemia) can lead to symptoms including headache, vomiting, coma, and, in some cases, even death.

High ammonia levels are most commonly caused by liver disease. The problem can also be caused by kidney failure and certain genetic disorders.

This article discusses the symptoms and treatment of high ammonia levels.

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Ammonia Levels

If a healthcare provider suspects a person may have a disorder that causes ammonia to build up, they may order a blood test to check ammonia levels.

Test results are often given in micrograms per deciliter (mcg/dL) or micromoles per liter (mcmol/L). If your results fall outside the normal range, it may not necessarily mean that an underlying health condition is present.

Ranges for lab values may vary slightly by the testing method used by the lab. Some labs may also use different measurements. It is important to speak with your provider to understand the meaning of your specific results.


Generally speaking, the normal ranges of blood ammonia levels are as follows:

  • Newborns: 85–271 mcg/dL (50–159 mcmol/L)
  • Infants and children: 41–82 mcg/dL (24–48 mcmol/L)
  • Female adults: 19–82 mcg/dL (11 –48 mcmol/L)
  • Male adults: 26–94 mcg/dL (15–55 mcmol/L)

This may vary by different laboratories and testing methods.


Higher than normal ammonia levels suggest that a person's liver cannot effectively excrete or process ammonia as it should, resulting in a buildup of toxic waste.

Because ammonia is toxic to the brain, there is no safe upper level of blood ammonia concentrations. However, a blood concentration above 150 to 200 mcmol/L is considered to be high. It can cause loss of brain function and even death.

Symptoms of High Ammonia Levels

Symptoms of high ammonia levels include:

When to See a Doctor

If you or someone you know is experiencing symptoms of high ammonia levels, call 911 or go to your nearest emergency room for evaluation.

Causes of High Ammonia Levels

High ammonia levels are commonly associated with kidney disease and liver disease.

Other causes include:

Hepatic encephalopathy: A condition that occurs when a person's liver is too damaged to process ammonia as it should. This causes a buildup of ammonia in the blood that eventually travels to the brain, causing confusion and disorientation. Sometimes, it may also result in a coma or death.

Urea cycle disorders: The urea cycle is a metabolic pathway that converts toxic ammonia into urea. A group of rare genetic disorders causes a partial or complete deficiency in one of the enzymes in the urea cycle. Without enough enzymes, the urea cycle isn't as effective at processing ammonia into urea.

Reye's syndrome: A rare disorder of childhood and adolescence that causes damage to the brain and liver. Although the exact cause of Reye's syndrome is unknown, it appears to affect children with viruses such as chickenpox or the flu who use aspirin (salicylates) to treat their symptoms.

Several other things can also cause elevated ammonia levels. These include:

  • Gastrointestinal bleeding
  • Parenteral nutrition (feeding through a vein)
  • Ureterosigmoidostomy (surgery to create a new way for urine to pass)
  • Salicylate poisoning
  • Elevated body temperature
  • Muscle exertion
  • Consuming a high-protein diet

Ammonia Levels Testing

The blood ammonia test, or NH3 test, is used to check ammonia levels in the blood. It is also commonly used to diagnose hepatic encephalopathy.

Testing involves taking a blood sample with a needle from a vein in your arm and sending it to a laboratory. The entire process is usually completed within five minutes.

Individuals are instructed not to exercise or smoke cigarettes for at least eight hours before the test.

Who Should Get Tested?

People who experience symptoms of high blood ammonia levels, such as sudden confusion, fatigue, or unconsciousness, should have their ammonia levels tested.

Additionally, your healthcare provider may also check your ammonia levels to assess the effectiveness of treatment for kidney failure or liver disease.


Lactulose (a laxative to treat constipation, with brand names including Generlac, Enulose, and others) is a first-line therapy often prescribed to decrease ammonia levels in patients with hepatic encephalopathy. It works by pulling ammonia from the blood into the colon, where it is removed through the stool.

Xifaxan (rifaximin), an antibiotic, is often prescribed for high ammonia levels because it can help reduce ammonia made in the intestines and improve brain function. If hepatic encephalopathy improves while taking Xifaxan, it should be taken until your doctor recommends that you discontinue it.

People who have urea cycle abnormalities may also require a low-protein diet to reduce the amount of ammonia produced by the body. In more severe cases, protein may be temporarily restricted.

Specialty low-protein formulas are available for toddlers and infants who require a protein restriction.

Dialysis, a procedure to remove waste products from the blood when the kidneys stop working, may also be used when ammonia levels are extremely high, to remove excess buildup.

If medical management is not successful, some people may also require a liver transplant.


Ammonia is a toxic waste product made by the body during digestion. Without proper treatment, high ammonia levels can lead to confusion, disorientation, and even death.

Although a higher than normal ammonia level does not always mean a medical condition is present, it is commonly caused by liver disease, urea cycle disorders, and kidney failure.

Treatment often involves medications such as lactulose and Xifaxan, which work to reduce ammonia levels. In more severe cases, dialysis or a liver transplant may be necessary.

If you or someone you know is experiencing symptoms of high ammonia levels, seek emergency medical attention.

A Word From Verywell

High levels of ammonia in the blood can lead to health problems. Because different laboratories can use different measurements and testing samples, it is important to always discuss your lab results with a qualified healthcare professional before self-diagnosing. Fortunately, with proper management and treatment, ammonia levels can be managed to avoid dangerous complications.

Frequently Asked Questions

  • What happens when your ammonia levels are too high?

    Elevated ammonia levels can cause serious health problems, including confusion, fatigue, coma, and even dealth.

  • How do high ammonia levels make you feel?

    Elevated ammonia levels can cause a person to feel confused, disoriented, or sleepy.

  • What is a critical ammonia level?

    There is no safe upper level of blood ammonia concentrations. However, concentrations above 200 mcmol/L are considered to be high and can result in loss of brain function and even death.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Science Direct. Hyperammonemia.

  2. Gupta S, Fenves AZ, Hootkins R. The role of RRT in hyperammonemic patients. Clin J Am Soc Nephrol. 2016;11(10):1872-1878. doi:10.2215/CJN.01320216

  3. MedlinePlus. Ammonia levels.

  4. Science Direct. Urea cycle disorder.

  5. National Organization for Rare Disorders. Reye syndrome.

  6. MedlinePlus. Ammonia blood test.

  7. MedlinePlus. Lactulose.

  8. MedlinePlus. Loss of brain function - liver disease.

  9. MedlinePlus. Hereditary urea cycle abnormality.

By Lindsey DeSoto, RD, LD
Lindsey Desoto is a registered dietitian with experience working with clients to improve their diet for health-related reasons. She enjoys staying up to date on the latest research and translating nutrition science into practical eating advice to help others live healthier lives.