Emergency contraception can prevent pregnancy, but the sooner you take it, the better.

By Lead writer: Louise Sloan
April 11, 2013
Plan B works best to prevent pregnancy if you take it up to 24 hours after unprotected sex.

Plan B works best to prevent pregnancy if you take it up to 24 hours after unprotected sex.(ANTHONY WEST/CORBIS)The morning-after pill, or Plan B, was FDA-approved in 2006 to be sold without a prescription as emergency contraception. It's available at most pharmacies, although you may need to ask the pharmacist for it. Once available only to women 17 or older, a 2013 court ruling overturned the age limit. Now anyone can buy Plan B without a prescription.

"Just ask the pharmacist and he'll give it to you," says Hilda Hutcherson, MD, an ob-gyn professor at Columbia University.

Plan B, which contains the same synthetic hormones found in birth control pills but in a higher dose, can prevent pregnancy from occurring if taken within 72 hours of unprotected sex. It may work up to five days after sex, but it works best when taken within 24 hours.

Since Plan B is more effective the sooner you take it, some health-care providers recommend having it on hand "just in case."

In 2010, the FDA approved ella, a contraception that is effective up to five days after sex. Ella blocks the hormones that are needed to conceive. Unlike Plan B, it is available only by prescription.

Emergency contraception should not be used as primary birth control, however. "Don't think, 'I'm only having sex four times a month, so I'll just take the morning-after pill every time,'" says Dr. Hutcherson. It's more expensive than other methods, may cause nausea, and will throw your cycles off. "Your body won't know what's going on," says Dr. Hutcherson.

More about that morning after

Note: Plan B is not the same as RU-486, the abortion pill. In fact, if you take Plan B and you're pregnant already, says Hutcherson, "You're gonna stay pregnant. Not gonna help you."