Ammonia Levels

Ammonia is a waste product that’s normally processed in your liver and removed through your urine. Sometimes, ammonia can build up in your blood, which can be very dangerous. Several conditions can cause high ammonia levels in your blood, including liver disease, kidney failure and certain congenital conditions.

What is ammonia?

Ammonia, also known as NH3, is a waste product that bacteria in your intestines primarily make when digesting protein. Normally, ammonia is processed in your liver, where it’s transformed into another waste product called urea. The urea is then carried to your kidneys, where it’s eliminated in your urine (pee).

If any part of this process, known as the urea cycle, is not working, ammonia builds up in your blood and can pass from your blood into your brain. The level of ammonia in your blood must remain very low. Even slightly elevated levels (hyperammonemia) are toxic to your central nervous system (CNS).


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What are normal ammonia levels?

Normal blood levels of ammonia vary according to age and are higher in newborns compared to older children or adults. In newborns, gestational and postnatal ages also affect the levels of ammonia.

  • Healthy term infants: 45±9 micromoles per liter (micromol/L); 80 to 90 micromol/L is considered to be the upper limit of normal.
  • Preterm infants: 71±26 micromol/L, decreasing to term levels in about seven days.
  • Children older than one month: Less than 50 micromol/L.
  • Adults: Less than 30 micromol/L.

Normal value ranges may vary slightly among different laboratories. Be sure to check your lab report’s reference range on your results. If you have any questions about your results, ask your healthcare provider.

What ammonia level is toxic?

Ammonia is highly toxic. Blood ammonia levels are usually less than 50 micromoles per liter (micromol /L), but this can vary depending on age. An increase to only 100 micromol /L can lead to changes in consciousness. A blood ammonia level of 200 micromol /L is associated with coma and convulsions.


How do you test ammonia levels in the body?

Your healthcare provider can measure the level of ammonia in your blood with a blood test. A healthcare provider will take a blood sample from a vein in your arm using a small needle and test tube to collect the blood.

To test a newborn, a healthcare provider will clean your baby's heel and poke their heel with a small needle. They will collect a few drops of blood and put a bandage on the site.

What are the symptoms of high ammonia levels?

Symptoms of high ammonia levels in your blood include:

  • Confusion and disorientation.
  • Excessive sleepiness.
  • Changes in consciousness.
  • Mood swings.
  • Hand tremors.
  • Coma.

If you or a loved one experiences these symptoms, call 911 or go to the nearest emergency room as soon as possible. High ammonia levels are life-threatening and require immediate medical treatment.

A healthcare provider may order an ammonia levels test may if your newborn has the following symptoms in the first few days after birth:

  • Irritability.
  • Vomiting.
  • Lethargy.
  • Seizures.


What causes high ammonia levels?

Causes of high blood ammonia levels include:

  • Liver disease: Damage to your liver limits its ability to process ammonia. This often happens in severe liver disease, but you can have spikes in ammonia blood levels with stable liver disease, especially following a triggering event such as gastrointestinal bleeding or an electrolyte imbalance. Liver disease is the most common cause of high ammonia levels.
  • Decreased blood flow to your liver: If there’s a lack of blood flow to your liver, your body can’t transfer ammonia to it to be processed. This causes ammonia to build up in your blood.
  • Hepatic encephalopathy: This is a condition that happens when your liver is too diseased or damaged to properly process ammonia, leading to a buildup of ammonia in your blood that travels to your brain. It can cause confusion, disorientation and coma. It can sometimes be fatal.
  • Reye’s syndrome: Reye’s syndrome is a rare condition that affects your blood, brain and liver that usually causes an increase in blood ammonia levels and a decrease in blood glucose. It mainly affects children and teenagers who are recovering from viral infections, such as chickenpox or the flu (influenza) and have taken aspirin to manage their symptoms. The cause of Reye’s syndrome is unknown, but because of the risk, children and teens should not take aspirin unless specifically recommended by their healthcare provider.
  • Kidney (renal) failure: If your kidneys are unable to effectively get rid of urea due to kidney failure, it leads to a buildup of ammonia in your blood.
  • Genetic diseases of the urea cycle: Certain rare genetic disorders can cause a deficiency in one of the enzymes necessary to complete the conversion of ammonia to urea, which is part of the urea cycle. This is usually discovered in infancy.
  • Hemolytic disease of the newborn: This disorder happens when a pregnant person develops antibodies to their baby's blood cells. This condition can be prevented. If you're Rh-negative and haven’t been sensitized, you can receive medication that stops your antibodies from reacting to your baby’s Rh-positive cells.

How are high ammonia levels treated?

The treatment for high ammonia levels depends partly on what’s causing it, such as liver disease or hepatic encephalopathy in adults or a congenital condition that disrupts the urea cycle in newborns.

Treatment of acute hyperammonemia focuses on decreasing the level of ammonia and controlling specific complications, including brain swelling (cerebral edema) and pressure around the brain (intracranial hypertension).

For newborns with high ammonia levels, healthcare providers stop protein intake (since protein digestion produces ammonia) and provide calories by using glucose solutions. Healthcare providers also use hemodialysis, a procedure where a dialysis machine and a special filter called an artificial kidney clean your blood, to remove ammonia from the newborn’s blood.

Medical treatment for hepatic encephalopathy involves decreasing the production of ammonia in your gut. The first-line therapy for encephalopathy is an oral medication that includes lactulose and lactitol. These sugars decrease the production and absorption of ammonia in your intestines.

When should I see my doctor about my ammonia levels?

If you or a loved one have symptoms of high blood levels of ammonia, such as confusion and excessive sleepiness, call 911 or go to the nearest emergency room.

If you have liver disease, you’ll need to see your healthcare provider regularly to make sure your liver is properly processing ammonia.

A note from Cleveland Clinic

While your body naturally produces ammonia as a waste product, it can be very dangerous if too much builds up in your blood. If you or a loved one have symptoms of high ammonia levels, such as confusion and excessive sleepiness, get to the nearest hospital as soon as possible. It’s especially important to be aware of these symptoms if you have liver disease since it can lead to elevated ammonia levels. If you have questions about your risk of developing high ammonia levels, talk to your healthcare provider. They’re there to help you.

Medically Reviewed

Last reviewed on 04/11/2022.

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