How long does it take the birth control shot to go in effect?

talking about the 3 month shot specifically. ??How long does it take the birth control shot to go in effect?
It works within a few days. Although so much is said as to why you shouldn't take this, I've never had a problem. I was on it for 10 years, I never had my period for the whole 10 years, I gained about 10 lbs, but so does everyone on any kind of birth control. I never had pms, no mood swings, no more headaches, caught less colds and flus, and never had to time trips or sex based on my period. When I stopped taking it, it took 2 months to get my period back and 8 months to get pregnant. I'm now 2 1/2 months pg. How long does it take the birth control shot to go in effect?
Right away...but don't take that ****. I will never forgive the doctors for letting me take that poison. 60 pounds, and massive heart problems later...here I am, off it for 7 months and still no period or baby. They say I may be infertile.
please i urge you to not take that shot i was on it once i gained alot of weight on it and i never stopped being on my period for 97days straight PLEASE TRY A DIFFERENT BIRTH CONTROL!!!
For all birth control, the first week you are advised to use a back-up method of birth control (condom or spermicide).





The shot really messed me up too though, I'm on the patch now and it's working much better. With the shot, the first year or so was ok (though I never got rid of my period like they said I would, I would start it about a week before I was due to get the next shot). After a year though, I started bleeding nonstop from about 4 weeks after each shot until I got my next 8 weeks later. I became anemic. I also had heart palpitations and asthma symptoms after never having asthma my whole life. Now that I'm on the patch, my periods are very very regular (every 28 days precisely) and not having these other problems.