Is it safe to have protein powder if i have autoimmune hepatitis (liver disease)?

You shouldn't experience any negative effects from taking the protein powder in relation to your liver disease. Most liver conditions actually put you at an increased need for protein (but you don't want too much either), since the impaired liver function can result in a difficulty in synthesizing/utilizing protein. One of the few exceptions is if you have hepatic encephalopathy, which sometimes indicates a lower protein diet. Most autoimmune disorders are managed medically though.

However, if you have any medical conditions, you should consult with your physician before starting any supplement.