How can I predict behavior changes in my father, who has hepatitis?

Reading your question, you do not say if your father has dementia or other serious medical problems, other than his hepatitis. If he is already sick or has dementia, and his behaviors are getting worse over time, it may just be due to his health failing or an increase in his dementia.

If your father's change in behavior is new, and he has otherwise been healthy, I would let his health care provider know right away. This may be a sign that something is going on with him. Since he has hepatitis, perhaps he is having some issues with his liver. Sometimes, the liver is unable to help detoxify the blood, and some harmful things can build up (like ammonia). There are meds that can help with liver diseases, so I would get him checked as soon as you can. Medications can certainly cause behavior changes, especially if someone is already frail at baseline. It is also possible that something happened to his brain, like a small stroke, or perhaps a dementia is starting. The best way to assess this is to get him an appointment to see his health care provider as soon as you can. Good luck!