Depo effectiveness

[Cjh01]

I got my first depo shot on Wednesday 11/28 in order to stop my period that lasted for 47 days. By Thursday my period had stopped. On 12/1 I had unprotected sex and am not sure if the depo is effective yet. I know that if it’s taken within the first 5-7 days of a period it’s immediately effective, but since mine was for so long I’m not sure how it works. Should I take a plan B just to be safe or should I be protected? It seems to me that the depo shot started working right away since my period stopped within 24 hours of the shot, but I just want to be sure since my period has been so crazy. Please help!

[Sam W]

Hi Cjh01,

If an appointment is scheduled at the correct time by a healthcare provider, a back-up method of birth control is only needed for the first 24 hours after the shot. If you're unsure as to whether that's what your healthcare provider did, it would be sound to give them a call and ask.

Just to check, since unprotected sex occurred, are you and your partner up to date on your STI tests?

[Cjh01]

My partner and I are recently married and we have both had normal STD/STI screenings. It wouldn’t be a huge deal to get pregnant, but we’re still young and don’t feel ready yet. I’ve never had the depo shot before 11/28. The only reason I got it was to stop my period. My husband and I have always used protection before, but since I am now on a type of birth control didn’t feel it was necessary. I’m just not sure what my risk for pregnancy is at this point. My primary doctor is out until Monday, so by then it would be too late to take a plan B.

[Siân]

Hi Cjh01,

If the shot was not scheduled at the correct time (e.g. because it's primarily to control your periods) then it may take up to 7 days to be fully effective. Did you discuss how long you'd need a backup method for with your doctor at the time?

Taken within 24 hours of unprotected sex, emergency contraceptive pills can reduce the risk of pregnancy by up to 98%; taken with 120 hours (5 days) after a risk, they may still be as much as 75% effective. This means that you could take emergency contraception on Monday after checking with your primary doctor, but it would be less effective than taking it today. More here: Emergency Contraception (Plan B or the Morning-After-Pill)