How does Plan B® work?

Plan B helps prevent pregnancy by temporarily delaying ovulation. That is, it works by stopping the release of an egg from the ovary, so there’s no egg to meet the sperm. No egg, no fertilization, no pregnancy.

Home / How Plan B® works

When did you have sex

without a contraceptive or have a contraceptive accident?

Please select a time earlier than the present.

You have hours remaining to take Plan B®.

The sooner you take Plan B®, the better it works. Plan B® can help prevent pregnancy if taken within 72 hours, and preferably within 12 hours, after a contraceptive accident or unprotected sex.

It has been more than 72 hours since you had unprotected sex or a contraceptive accident. Please contact a healthcare professional for advice.

Back Find a pharmacy

It’s called Plan B for a reason

Unlike regular birth control methods, which are used before or during sex, Plan B® is used to prevent pregnancy after unprotected sex or following a contraceptive accident.

Plan B® is available as a single pill (levonorgestrel 1.5 mg). It must be taken within 72 hours after unprotected sex or birth control failure. The sooner you take it, the better it works.

Available for all women who need it

Plan B® is the best-selling brand of emergency contraceptive in Canada.* Find it on the shelf at your local pharmacy.†

Find a pharmacy

How does Plan B®
prevent pregnancy?

Each Plan B® tablet contains 1.5 mg of levonorgestrel—an ingredient that is also commonly found in birth control pills.

When taken correctly (within 72 hours of a contraceptive accident or unprotected sex), Plan B® works by:

  • Temporarily stopping the release of an egg from the ovary (ovulation)

Plan B® is not an abortion pill—it will not work if you are already pregnant & will not affect an existing pregnancy.

*SDM Nielsen sales data, 2022.
†Except in Québec (where you will need to speak to the pharmacist).