Hyperammonemia is a condition in which a person has elevated levels of ammonia. Typical symptoms include irritability, vomiting, confusion, and other effects of swelling in the brain.

People of all ages can develop hyperammonemia. Newborn babies may have it due to genetic defects, while adults can develop the condition as a result of liver disease.

Hyperammonemia can be a serious and potentially life threatening condition. A person with symptoms of hyperammonemia should contact their doctor for a diagnosis and prompt treatment.

This article discusses the symptoms and causes of hyperammonemia, as well as treatment options, risk factors, and more.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Hyperammonemia is a medical term used to describe abnormally high levels of ammonia. This can disrupt bodily functions, particularly the nervous system and kidneys.

The human body normally produces ammonia, most often as a byproduct of digesting protein. A healthy body reuses ammonia or processes ammonia in the liver, where it is turned into urea and excreted.

Hyperammonemia develops when this process breaks down, and ammonia levels rise beyond healthy levels.

Hyperammonemia can be acute, which means it has a sudden onset, or chronic. It has many potential causes, which also makes it difficult to determine how common it is. Roughly 1 in 250,00 infants born in the United States has a urea cycle disorder, which is one of the potential causes of hyperammonemia.

Ammonia is neurotoxic, which means it is poisonous to the nervous system. It should be identified and treated as soon as possible.

Symptoms of hyperammonemia can differ depending on who is affected.

Symptoms in adults

Symptoms in adults can include:

  • changes in sleep patterns
  • headache
  • lack of appetite
  • vomiting
  • confusion
  • slurred speech
  • shaking hands
  • poor concentration
  • poor muscle control
  • changes in walking
  • seizures
  • coma

Symptoms in children

Children may develop symptoms of Reye’s syndrome, which is a serious condition that causes damage to the brain and liver.

Symptoms may include:

  • vomiting
  • irritability
  • sleepiness
  • seizures

Learn more about Reye’s syndrome.

Symptoms in newborns

Newborns can show signs of hyperammonemia in their first 24–72 hours. These can include:

  • lethargy
  • irritability
  • vomiting
  • hyperventilation
  • grunting

Hyperammonemia can be due to genetic disorders or acquired health problems, such as liver disease or kidney failure. Around 90% of hyperammonemia cases in adults are related to cirrhosis of the liver.

Learn more about cirrhosis.

Other causes of hyperammonemia include:

  • urea cycle disorders (UCD)
  • disorders of the blood or blood-forming organs, such as acute leukemia or multiple myeloma
  • infections, such as urinary tract infections in children with congenital defects or older adults
  • urea cycle defects that become apparent due to stressors such as seizures, starvation, or gastrointestinal bleeding

A UCD is a genetic condition that prevents the body from breaking down ammonia, converting it into urea, and eliminating it. This results in ammonia building up in the body.

A person with underlying problems with their urea cycle may develop hyperammonemia when their bodies are put under serious stress or due to certain situations, such as:

Cirrhosis and genetics are significant risk factors for hyperammonemia.


Since most cases of hyperammonemia in adults are due to cirrhosis, identifying factors that may contribute to the development of cirrhosis can shed light on risk factors for hyperammonemia.

Some risk factors for cirrhosis of the liver include:

  • obesity
  • diabetes
  • excessive alcohol consumption, which is more than 1–2 alcoholic beverages per day for females or more than 2–3 alcoholic beverages per day for males
  • having had chronic viral hepatitis

Obesity and diabetes are listed as risk factors for cirrhosis because nonalcoholic fatty liver disease (NAFLD) is more common in people who have diabetes or obesity. NAFLD causes swelling in the liver, which can lead to scarring, or cirrhosis.

Learn more about NAFLD.


Genetics are a risk factor for hyperammonemia. The most common type of UCD is due to a problem with the X chromosome.

If a male inherits this deficiency, they are likely to have UCD symptoms. If a female inherits the deficiency, they may or may not have symptoms, but they can pass the faulty gene along to their future children.

A person can also inherit a UCD through mutation or by receiving copies of the malfunctioning gene from both parents.

Diagnosing hyperammonemia varies according to the age of the person involved.

Measuring levels of ammonia with blood tests is one of the key methods for diagnosing hyperammonemia. Normal levels vary with age, as noted for the following age groups:

  • Preterm infants: 71 micromoles per liter (mcmol/L) plus or minus 26 mcmol/L, dropping to levels for infants born at term within around 7 days
  • Full-term infants: 45 mcmol/L plus or minus 9 mcmol/L (80–90 mcmol/L is the upper limit for a typical level)
  • Children older than 1 month: less than 50 mcmol/L
  • Adults: less than 30 mcmol/L

Ammonia levels above 100–150 mcmol/L can lead to hyperammonemia symptoms in newborns.

In adults, tests to measure levels of liver enzymes, bilirubin, and prothrombin time help physicians assess liver function.

Additional tests are required for preterm infants with hyperammonemia symptoms to rule out other conditions, such as sepsis, gastrointestinal bleeding, meningitis, and intracranial hemorrhage.

Treating hyperammonemia focuses on lowering ammonia levels and managing any complications the condition may cause.

Treatment is adjusted according to a person’s age and what causes their hyperammonemia. Possible treatments include:

  • hemodialysis, hemofiltration, and intravenous medications for preterm infants with serious complications
  • intravenous glucose solutions and medications, as well as dialysis if needed for adults with underlying urea cycle defects
  • oral antibiotics and medication to decrease ammonia production for adults with liver-related neurological problems
  • supplements of essential nutrients in adults with urea cycle defects and liver-related neurological problems

Researchers are also exploring the possibility of working with the gut microbiota to treat hyperammonemia and other diseases attacking the nervous system.

Learn more about treatments for high levels of ammonia.

Hyperammonemia is a medical term used to describe abnormally high levels of ammonia. Ammonia is neurotoxic, which means it is poisonous to the nervous system. The condition should be identified and treated as soon as possible, as it can lead to life threatening complications if left untreated.

Hyperammonemia can be due to genetic disorders or acquired health problems, such as liver disease or kidney failure. Treatment for hyperammonemia focuses on lowering ammonia levels and managing the complications the condition causes.

Treatment may depend on the underlying cause but can include intravenous medications and glucose solutions, hemodialysis, hemofiltration, oral antibiotics, and nutrition supplements.