What causes elevated ammonia levels?

An elevated ammonia level (or hyperammonaemia) in the blood is usually due to liver dysfunction, either because of a genetic problem with the enzymes that metabolise ammonia, or because of acquired liver disease, for example from alcoholic cirrhosis or hepatitis.

Symptoms of elevated ammonia levels

An elevated ammonia level produces non-specific symptoms such as:

  • Decreased appetite
  • Lethargy
  • Rapid or heavy breathing
  • Irritability
  • Altered mental state.

This may occur because of decreased breakdown of ammonia in the body from two main causes:

  • Liver disease, especially liver failure
  • Genetic metabolic defects – the family of related conditions known as ‘urea cycle defects’

Usually these congenital enzyme abnormalities are diagnosed early in life because of severe metabolic consequences. A clue may be exaggerated lethargy or vomiting with episodes of minor illness, such as those due to viral infections.

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How are ammonia levels tested?

Ammonia level (NH3) is a blood test and requires a few millilitres of blood from a vein. The specimen is usually transported on ice to the laboratory to be analysed.

Related specialists

Related procedures

  • Blood Test (venesection)

Related tests

Also known as

  • Plasma Ammonia level
  • Serum Ammonia level

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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.

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