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What is ammonia blood test?

An ammonia blood test measures the amount of ammonia in your blood. Ammonia is a waste product made by your body during the digestion of protein. Your body normally converts ammonia into urea, which is expelled from your body in urine. However, if there is too much ammonia in your blood, it could indicate a problem with your liver or kidneys.

Why do doctors order ammonia blood tests?

There are several reasons why your doctor may order an ammonia blood test:

  • To check liver function – The liver converts ammonia into urea. Liver diseases like cirrhosis or hepatitis can reduce the liver’s ability to rid the body of ammonia. Increased blood ammonia levels may indicate liver dysfunction.
  • To monitor severe liver disease – Ammonia levels are frequently monitored in people with severe liver disease to help guide treatment and prevent complications like hepatic encephalopathy (brain dysfunction due to liver failure).
  • To evaluate kidney function – The kidneys also play a role in removing ammonia from blood. Kidney dysfunction can lead to increased ammonia.
  • To investigate urea cycle disorders – The urea cycle is the process that converts ammonia into urea. Genetic disorders that affect enzymes involved in the urea cycle cause ammonia to accumulate.
  • To monitor people in comas – Increased ammonia seen in some unconscious patients can cause brain swelling and coma. Checking ammonia levels helps identify this issue.
  • To diagnose Reye’s syndrome – Increased ammonia is one of the hallmarks of Reye’s syndrome, a rare but life-threatening condition that can affect children after viral infections.

Doctors may order ammonia testing in infants with vomiting and lethargy to screen for urea cycle disorders or organic acidemias that can cause dangerously high ammonia levels.

What is normal range for ammonia level?

Normal ammonia levels can vary somewhat from lab to lab. A normal range is typically between 10-50 micromoles per liter (μmol/L).

Newborns can have higher values up to 80 μmol/L. Levels typically decrease throughout infancy and childhood.

In adults, ammonia levels above 50 μmol/L are generally considered elevated. Levels above 100 μmol/L usually indicate more severe liver dysfunction.

Dangerously high levels above 150 μmol/L can lead to brain swelling and coma. However, there is no definitive ammonia level that causes symptoms. Some individuals experience brain symptoms like confusion at lower levels while others tolerate higher values without issues. The timeline of how quickly ammonia rises also plays a role.

How is the ammonia blood test performed?

Before the test:

– No special preparations are required.

– Medicines and supplements are usually continued as normal, but your doctor will provide instructions if you need to hold or change doses.

– Strenuous exercise is avoided right before the test as it can temporarily raise ammonia levels.

During the test:

– A small sample of blood is drawn from a vein, usually in your arm.

– In infants or young children, blood may be obtained by a heel prick.

– The procedure takes just a few minutes.

After the test:

– Pressure is applied on the puncture site to avoid bruising.

– You can resume normal activities.

How to interpret ammonia blood test results?

Some key things to know when interpreting your ammonia test results:

  • Higher levels typically reflect greater severity of liver dysfunction. However, symptoms do not always correlate with ammonia levels.
  • Levels between 50-100 μmol/L are usually investigated further to determine the cause.
  • Levels above 100 μmol/L often indicate advanced liver disease. Hospitalization may be needed to treat high ammonia.
  • Very high levels above 150 μmol/L can lead to cerebral edema (brain swelling). This is a medical emergency requiring intensive treatment.
  • Trends in ammonia levels over time provide more useful information than a single value. Doctors monitor ammonia to see how it changes with treatment.
  • Falsely low ammonia levels can sometimes occur if the sample was not processed quickly enough. Falsely high levels may result from hemolysis (ruptured red blood cells) in the sample.
  • Ammonia level alone does not provide enough information for diagnosis. Other lab tests and clinical information are also considered.

Discuss your results thoroughly with your doctor to understand what they mean for your health situation.

What causes high ammonia levels?

Some potential causes of elevated blood ammonia include:

  • Liver disease – Cirrhosis, viral hepatitis, Wilson’s disease, alpha-1 antitrypsin deficiency
  • Medications – Valproic acid, chemotherapy drugs
  • Gastrointestinal bleeding – Blood in the GI tract is digested, releasing ammonia
  • Infection – Sepsis, urinary tract infections
  • Kidney disease – Acute kidney injury or chronic kidney disease
  • Genetic disorders – Urea cycle defects, organic acidemias
  • Toxic ingestions – Methanol, ethylene glycol
  • Prolonged fasting or vigorous exercise – Causes breakdown of amino acids and increased ammonia
  • Ammonia-producing intestinal bacteria – Certain bacterial overgrowth syndromes

Identifying the underlying cause is crucial for guiding appropriate treatment to lower ammonia.

What causes low ammonia levels?

While high ammonia is more concerning clinically, causes of lower than normal ammonia include:

  • Malnutrition or protein deficiency
  • Pregnancy
  • Overhydration
  • Amyloidosis
  • Rare genetic deficiencies affecting ammonia production

Mildly low ammonia is typically not dangerous. Very low levels may be investigated for underlying causes.

How is high ammonia treated?

The goal of treating elevated ammonia is to:

1. Lower ammonia production

2. Support pathways that convert ammonia to urea

3. Enhance ammonia excretion

This is achieved through a combination of medications, diet changes, and treating any underlying diseases:

  • Medications – Lactulose decreases ammonia absorption from intestines. Rifaximin decreases ammonia production by gut bacteria. Sodium benzoate and sodium phenylacetate help excrete ammonia.
  • Dietary changes – Restricting protein intake to minimum requirements avoids excess ammonia from protein breakdown. High carbohydrate intake promotes ammonia excretion.
  • Treating underlying conditions – This may include antibiotics for infections, dialysis for kidney failure, or medications to manage liver disease.
  • Liver transplant – For people with advanced liver failure and recurrent episodes of very high ammonia, a liver transplant may be life-saving.

When ammonia levels are acutely and severely elevated, dialysis can rapidly clear ammonia from the bloodstream.

Can you lower ammonia levels through diet?

Diet can have a significant impact on ammonia levels. Some tips for an “ammonia-lowering” diet include:

  • Limit protein intake to approximately 0.8 grams per kilogram of body weight per day.
  • Avoid high protein foods like meats, eggs, and dairy. Get protein from plant sources like beans and nuts.
  • Eat small, frequent meals instead of large ones to steady protein absorption.
  • Increase carbohydrates through fruits, vegetables, whole grains and sweetened foods. Carbs help eliminate ammonia.
  • Avoid foods high in amino acid content like spinach, nuts, and soy products as these create more ammonia when digested.
  • Avoid processed and fermented foods that contain ammonia compounds.
  • Stay well hydrated with non-caffeinated beverages like water and juices to flush out ammonia.

Consult a nutritionist or registered dietician to formulate a balanced, low protein diet tailored to your condition. Carefully monitor ammonia levels to see if dietary changes help reduce the values.

What are symptoms of high ammonia?

Ammonia is neurotoxic, meaning it damages the brain. The severity of symptoms tends to correlate with the height of the ammonia level.

Mild symptoms of elevated ammonia may include:

– Headache, lightheadedness
– Lethargy, sleepiness
– Vomiting
– Difficulty concentrating
– Mood changes like irritability

More severe symptoms indicating very high ammonia levels can include:

– Disorientation, confusion
– Slurred speech
– Combativeness, bizarre behavior
– Hallucinations
– Seizures
– Somnolence leading to coma

Rapidly rising blood ammonia causes cerebral edema (brain swelling), which can have life-threatening consequences if not treated urgently.

Symptoms like headache and nausea may start around the 50-100 μmol/L range. Changes in consciousness, cognition and behavior typically occur at levels above 100-150 μmol/L. However, there is no set threshold when symptoms start. The timeline of how quickly ammonia rises also influences the effects.

Can you feel symptoms of high ammonia?

Many people with mildly or moderately elevated ammonia have no symptoms at first. Often, ammonia is checked as part of laboratory workup for another condition, and is found to be high.

However, as ammonia climbs above 100-150 μmol/L, most people will experience recognizable symptoms like:

– Confusion, difficulty thinking
– Drowsiness, sleepiness
– Lack of coordination (ataxia)
– Slurred speech (dysarthria)

Severe symptoms will present suddenly once ammonia is very highly elevated, usually above 150 μmol/L. These include:

– Disorientation, inability to focus thoughts
– Combativeness, agitation
– Hallucinations, delusions
– Lethargy leading to coma

Ammonia encephalopathy (brain dysfunction due to high ammonia) can resemble drunkenness with bizarre behavior, stupor and eventual coma.

Seek emergency medical help if you or a loved one develop these types of mental status changes which may signify dangerously high ammonia. The longer hyperammonemia persists, the higher the risk of permanent brain damage.

What are ammonia poisoning symptoms?

Ammonia poisoning is rare but can occur from swallowing or inhaling concentrated ammonia products. Symptoms include:

– Burning pain in mouth, throat, nose, eyes and skin
– Difficulty swallowing
– Wheezing, shortness of breath
– Hypersalivation (excessive drooling)
– Nausea and vomiting
– Abdominal pain

If ammonia poisoning is suspected:

  • Call 911 or emergency medical services immediately
  • Avoid further exposure by leaving the area if ammonia gas or liquid is still present
  • Remove any contaminated clothing and rinse skin and eyes thoroughly with water
  • Inhaling ammonia can cause life-threatening swelling in the throat and airways

With severe exposure, respiratory failure can occur along with chemical burns to the skin and eyes. Seek medical attention even if initial symptoms seem mild, as damage can progress over the hours following exposure.

Takeaway messages about ammonia blood testing

  • Ammonia blood testing measures the amount of ammonia in the bloodstream.
  • Elevated ammonia may indicate liver or kidney dysfunction. It is commonly seen in advanced liver disease.
  • Normal ammonia levels are around 10-50 μmol/L. Levels above 100-150 μmol/L often cause neurologic symptoms.
  • Diet changes, medications, dialysis and treating underlying diseases can help lower high ammonia.
  • Rapidly rising blood ammonia above 150 μmol/L is a medical emergency requiring intensive treatment.
  • Symptoms like confusion, combativeness and coma should prompt urgent evaluation for hyperammonemia.

Ammonia testing provides vital information to help diagnose conditions leading to impaired ammonia metabolism, monitor their severity, and guide treatment to normalize levels. Work closely with your doctor to understand the role of ammonia in your health situation.


The ammonia blood test is an important tool to evaluate liver and kidney dysfunction which impair the body’s ability to eliminate ammonia. Elevated levels can have serious neurological consequences if left untreated. Doctors utilize ammonia testing to help diagnose conditions causing hyperammonemia, monitor disease severity, and determine if treatments are effectively lowering levels. Prompt evaluation of symptoms like disorientation and coma is crucial, as rapidly rising ammonia can quickly turn life-threatening. With a measured approach and proper medical care, steps can be taken to regulate ammonia and prevent further complications.