Do you ask for finasteride first visit?

Hello, I had my first visit with my PCP. We talked about my transition goals, informed consent, etc. When I mentioned hair loss as one of my concerns they brought up finasteride. I asked if I could have a script for Fin but she said it was more effective at treatment than prevention and I guess I just want some more advice for those already on it? I accept that MPB is going to be a risk factor while being on T but if I can take precautions early on then that’s even better. I love my hair and will go lengths to try and protect it especially this early on.