Answers to Frequently Asked Questions About...
How to Use Emergency Contraception
What if I take the second dose of emergency contraceptive pills late?
Two-dose levonorgestrel EC pills are no longer sold in the United States, although they are still available in many other countries. The instructions for 2-pill progestin-only emergency contraceptive products may say that you should take two doses 12 hours apart (that’s one pill followed 12 hours later by another pill.) However, research shows that progestin-only emergency contraceptive pills (also called "morning after pills" or "day after pills") are equally effective if you take the two doses at the same time, take them 12 hours apart as recommended, or wait as long as 24 hours to take the second dose.
Plan B One-Step, Take Action, Next Choice One Dose and My Way are single-pill products that contain 1.5 mg levonorgestrel. Take the pill as soon as possible after sex. Similarly, ella (ulipristal acetate) is just one pill that you take as soon as possible after sex (in clinical studies, the effectiveness of ella doesn't decline over a 5-day period, but for each individual woman, what's important is where she is in her own cycle; emergency contraceptive pills don't appear to work after ovulation has occurred).
Research about “combined” emergency contraceptive pills (those are pills containing both estrogen and progestin, such as regular birth control pills used in different doses as EC), in contrast, has focused on taking the two doses 12 hours apart. Even so, taking the second dose a little early or a little late (like a difference of two hours) will probably not make a difference in how effective the pills are.
A thorough and up-to-date academic review of research about how and when to take emergency contraceptive pills, as well as other medical and social science literature about emergency contraception is available here .