A high blood ammonia level occurs due to the failure of the liver to convert the ammonia in the blood to urea, as stated by WebMD. This may be caused by different conditions, such as severe hepatitis and cirrhosis. This can also be associated with hepatic encephalopathy, an infection that occurs when the liver fails to perform its functions.
The main function of the liver is to get rid of toxins from the blood, which are then removed from the body through the urine. If the liver is damaged, toxins are accumulated in the bloodstream. Ammonia buildup may also be caused by an urea cycle disorder, as stated by the University of Rochester. Ammonia is made in the body during the digestion of proteins. Its accumulation in the body together with other toxins may cause a damage to the nervous system if the liver is damaged, as stated by MedlinePlus.
Undergoing a test to determine the level of ammonia in blood can help detect a childhood disorder called Reyes Syndrome, which affects the liver's function, as stated by WebMD. During the test, a doctor will take a blood sample from a person and send it out to be lab tested.