Also known as “Plan B,” it can be taken up to 3 days (72 hours) after unprotected sex or contraception failure. The sooner you take it, the better it is at preventing pregnancy. Levonorgestrel pills are available over-the-counter, without a prescription (you may need to ask for them at the pharmacy counter), for people of all ages.
This one-dose pill blocks the hormones your body needs to conceive. It can be taken up to 5 days after unprotected sex or contraception failure. Ella requires a prescription from your healthcare provider.
Emergency contraception pills like levonorgestrel-based pills and Ella prevent pregnancy in several ways. It works mainly by preventing ovulation (when the ovary releases an egg) and thickens cervical mucus so sperm cannot reach an egg. Taking either of these does not protect you from sexually transmitted infections (STIs) or another possible pregnancy if you have unprotected sex again.
Learn how exactly emergency contraception works in this video by AsapScience.
Emergency contraception is most effective when taken as soon as possible after unprotected sex or contraception failure. The number of people who will become pregnant after using emergency contraception:
- Plan B (levonorgestrel-based pills): 15-26 out of 1,000 people
- Ella (ulipristal acetate): 12-18 out of 1,000 people
- Hormonal IUD: 3 out of 1,000 people
- Copper IUD: 1 out of 1,000 people.
There are no serious long-term side effects of using emergency contraception. In the short-term, it can cause:
- Plan B and Ella: nausea, vomiting, earlier or later menstruation (periods), heavier or irregular bleeding, or spotting
- Hormonal IUD: pain or discomfort with IUD placement, cramping after placement, breast tenderness, mood changes, irregular bleeding or spotting
- Copper IUD: pain or discomfort with IUD placement, cramping after placement, increased menstrual cramping, irregular bleeding or spotting
Emergency contraception pills are only recommended as a backup and should not be used as a primary method of birth control.
To learn more about the birth control methods available, visit our Family Planning and Birth Control page.
For more information about emergency contraception:
A quick note about emergency contraceptives and body weight: Some research has found that levonorgestrel (Plan B) is less effective for those who weigh more than 165 pounds or have a BMI of 25 or more (calculate your BMI here). Because the data isn’t clear, the FDA does not believe a change in labeling to exclude the use of Plan B in any person, regardless of how much they weigh, is needed at this time.
Other options for emergency contraceptives for those with larger bodies include ulipristal acetate (Ella) or a copper or hormonal IUD. Ella may not be as effective if the patient’s BMI is 35 or more, but the copper and hormonal IUDs do not seem to be affected by weight.