I would not go out of my way to volunteer the info. In my case, I was pointedly asked why I wanted to start giving blood now, being that I am middle aged and had not donated before. So I said that my doctor prescribed hormone treatments might make it a good idea to donate.
I didn't really want to go there, but I like to be completely honest whenever possible, and I think they can figure it out anyway.
As long as you don't take finasteride, or your hematocrit is already too high, or you are unable to state that you have never injected something not prescribed by your doctor, you should be ok to donate.