PETOGEN 150 MG INJECTION starts working immediately if given within the first 5 days of beginning of your periods. But, if you receive the dose at another time of your menstrual cycle then it may take about 7 to 10 days to show effectiveness.

How long does it take for a prevention injection to be active?

When it starts to work

If you have the injection during the first 5 days of your menstrual cycle, you'll be immediately protected against becoming pregnant. If you have the injection on any other day of your cycle, you'll need to use additional contraception, such as condoms, for 7 days.

Can you fall pregnant while on the 3 month injection?

If you're using the birth control shot correctly, which means getting it every 12-13 weeks (3 months), it's highly unlikely that you'll get pregnant. Only 6 out of 100 people get pregnant each year while using the shot.