it takes a loooong time to build up. i felt a little something in 2 weeks, but only felt a serious reduction in symptoms (i took it for panic disorder and ocd symptoms, labeled unofficially by the practitioner) after 3 months.
taking it also made me realize i have depression, because all of a sudden i had what i felt was an immense amount of energy to do everything people are generally 'supposed to.' 4+ hours of housework a day, the whole shower and oral care routine people normally follow, personal projects, my daily steps went from like, 200, to 7k unintentionally. i actually cooked and made meals, felt hunger. i really thought all that daily to-do crap was performative and no one actually did it without someone else to spectate or impress.
after 8 (?) months, i stopped unintentionally. i had noro for 2 weeks which had me convinced i'd just puke it up again, and so i got out of the habit of taking it. despite stopping and being inconsistent when i tried to take it again, the panic disorder and such didn't come back. figured i didn't need it anymore, though the depressive symptoms came back. suicidality came about recently once i was well off the medication; can't comment on how effect prozac is for that specifically since i only took it because of the disabling panic disorder. i don't feel the need to get rid of my suicidal ideation or depressive symptoms, so i wouldn't even try getting back on it just for that.
also, i stuck to 10mg. my provider tried to push me to 20, then 30, but it aggravated my anxiety badly and i insisted on staying at 10 which had been working fine.