The sources of blood ammonia are: i. ammonia produced by the decomposition and metabolism of amino acids in various tissues of the body, which is the main source of ammonia in the body; ii. ammonia absorbed from the intestine, which is produced by the decomposition of nitrogenous compounds by intestinal bacteria, so excessive protein intake can lead to excessive ammonia production in the body; iii. renal tubular epithelial cells can secrete a small amount of ammonia; iv. ammonia produced from the decomposition and metabolism of other nitrogenous compounds. The main routes of blood ammonia are: i) most of the ammonia is synthesized in the liver as urea, which is the main route of ammonia metabolism; ii) non-essential amino acids such as glutamine are synthesized; iii) a small amount of ammonia is excreted in the kidney as amine salts; iv) it is transformed into other nitrogenous compounds, and the balance of blood ammonia is also a dynamic balance.