I had the shot injected in my bum, it’s meant to last for 3 months in your system, so you have to renew it every 3 months. It begins to work immediately after the shot has been injected in you. Oh baby there is no return with this one, so you basically have to live with all the side effects for 3 months. It’s was a hell of a 3 months for me as I experience almost all it side effects lol (I’m laughing now but I wasn’t laughing before). Personally I wouldn’t advise anyone to go on this pill because if this was the only birth control method on planet, I will just abstain from sex. It takes time for your body to adjust to it’s normal state again. Got it done for free at the clinic.