i have the flu and want to go out for birthday dinner with some friends and I tell my friend i tell my friend I might not be able to go my friend won’t take no for an answer what is the decision i should make?

I think you shouldn't go. If you care about your friend(s) health, then you shouldn't be going out, especially with the flu. You might get them sick, and others as well. It's important that you should take care of yourself, rather than going out and probably, with a high chance, catch the virus. Please stay safe, even if your friend(s) gets upset I'm sure they will forgive you. <3