What reason would cause the ammonia level in your body to go up to 120? Is it due to kidney failure this is a question about my 81 year old father

Ammonia level. Ammonia level is moat likely due to kidneys not working effectively, but there are other rare causes. Your dad needs to see a doctor very soon.
An . An elevated blood ammonia level is usually due to liver failure. High blood ammonia levels can cause serious symptoms including severe confusion and even coma. Patients with severe liver problems can also have kidney failure as well due to the so-called hepatorenal syndrome.