Updated: Oct 21, 2013
  • Author: Sridevi Devaraj, PhD, DABCC, FACB; Chief Editor: Thomas M Wheeler, MD  more...
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Reference Range

The lower limit of the reference range is 10-20 μmol/L.

The upper limit of the reference range is 35-65 μmol/L.



Conditions Associated with “high” ammonia levels include the following:

“High” ammonia levels when combined with decreased glucose levels include the following:

Conditions associated with “low” ammonia levels include the following:

Other states associated that can affect ammonia levels include the following:

Drugs that can increase ammonia levels include the following:

  • Alcohol
  • Barbiturates
  • Diuretics
  • Valproate
  • Narcotics
  • Smoking

Collection and Panels

Specifics regarding collection and panels are as follows:

  • Specimen type: Blood plasma; serum not acceptable, urine ammonia
  • Container: Vacutainer (chilled heparin tube)
  • Collection method: Venipuncture

Blood should be brought on ice within 10 minutes to the laboratory for testing.

  • Panels: Urine analysis
  • Related test: Liver panel



Ammonia is a compound produced by intestinal bacteria and cells during the digestion of protein. It is transported through the portal vein to the liver, where the ammonia is converted to glutamine, which is metabolized by the kidneys into urea to be excreted. If the liver is diseased, the ammonia is not broken down and builds up in the blood. It can pass through the blood/brain barrier, where it can accumulate and cause hepatic encephalopathy. This condition causes mental changes that can lead to mental and neurological changes that manifest themselves as confusion, disorientation, and sleeplessness. If not treated, patients may experience seizures, difficulty in breathing, and lapse into a coma. [2, 3, 4, 5]


The test is used to help determine the cause of changes in behavior and consciousness, to confirm a diagnosis of Reye syndrome or hepatic encephalopathy caused by liver disease, or to evaluate a urea cycle defect or to investigate the cause of coma of unknown origin

Indications for test in newborns include the following:

  • Irritability
  • Vomiting
  • Lethargy
  • Seizures in the first few days following birth

Indications for the test in children in whom Reye syndrome is suggested include the following:

  • Irritability
  • Vomiting
  • Lethargy
  • Seizures following a viral illness
  • Infection
  • Cold

Indications for the test in adults include the following:

  • Mental changes
  • Sleepiness
  • Coma
  • An acute change for the worse in patients with liver disease
  • To check levels in a person receiving high-calorie IV nutrition (hyperalimentation)

Causes of problems in metabolizing/breaking down ammonia include the following:

  • Liver disease
  • Decreased blood flow to the liver
  • Reye syndrome (increased ammonia and decreased glucose)
  • Renal failure
  • Inherited defects in the urea cycle enzyme deficiency
  • Hemolytic disease of the newborn

Causes of increased ammonia levels in patients with advanced liver disease include the following:

  • High protein intake
  • Gastrointestinal bleeding
  • Hypokelemia
  • Metabolic alkalosis
  • High-dose chemotherapy
  • Parenteral nutrition
  • Renal insufficiency
  • Shock
  • Ureterosigmoidostomy

Note: In hepatic encephalopathy, brain levels of ammonia may be much higher than blood ammonia levels.


The test measures the amount of ammonia in the blood. Patients should not smoke before collection of the sample.

Because other waste products can result in changes in mental and neurological performance, the ammonia level may not correlate accurately with the patient's symptoms.

Glucose levels over 500 mg/dL may interfere with the test.