Other names: Plasma Ammonia

Ammonia is a waste product, which is produced by intestinal bacteria; ammonia is also produced when the cells break down proteins during digestion. Ammonia is usually converted into urea by the liver and then taken to the kidneys, where it is expelled from the body in the urine. If ammonia is not broken down and excreted, it starts to build up in the blood.

What is the test used for?

The ammonia test is used to assess the levels of ammonia in the blood; the test is used to diagnose genetic urea cycle disorders, Reyes Syndrome and severe liver disease. The test is usually recommended for those who have fallen into a coma without any known reason; the test is also used for infants and children who vomit repeatedly without an apparent cause.

How is the test performed?

The test is done using a sample of blood, which is collected from a vein in the arm. The veins will be encouraged to swell by placing a tourniquet on the upper arm; this will make it easier for the doctor or nurse to get the needle into the vein and collect the sample. Once the sample has been collected, it will be bottled and the patient’s name will put on the bottle; it will then be sent off to the laboratory for analysis.

It is important that the patient does not smoke for a set period of time before the test is carried out; your doctor will discuss with you when you arrange to have the test done.

What do the results show?

High levels of ammonia in the blood show that the body is not effectively breaking down and excreting ammonia; however, the results do not show the cause of this. In very young babies, high levels of ammonia usually show an inherited deficiency in the urea cycle; however, this may also be caused by haemolytic disease of the newborn.

If ammonia levels are high and glucose levels are low, this may indicate that an individual has Reye’s syndrome, a rare but very serious condition which affects the brain.

High levels of ammonia may also indicate kidney or liver damage or may be caused by the following factors:

  • Smoking
  • Physical exertion (the muscles produce ammonia when they are contracting)
  • Certain types of drug, including narcotics, barbiturates and alcohol

Specific Blood Tests

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