Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. For regularly updated information on a variety of health topics, please visit, the AAFP patient education website.

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Am Fam Physician. 2004;70(4):717-718

What is emergency birth control?

Emergency birth control is a method of birth control that you can use to keep from getting pregnant if you have unprotected sex. You can use this method if your regular birth control fails (for example, if you are using a condom and it breaks during sex) or if you have sex without using any birth control.

There are two kinds of emergency birth control. The first kind is two doses of birth control pills. The other kind is an intrauterine device (also called an IUD) that is placed in your uterus (or womb).

How do I use emergency birth control?

Emergency birth control (sometimes called the “morning-after pill”) is taken in two doses. You can start taking the pills right away after having unprotected sex. You should take the first dose within 72 hours of having unprotected sex. The sooner you take it, the better it works. You take the second dose 12 hours later. Your doctor may tell you about other ways of taking this medicine.

Two brands of pills have been made just for emergency birth control. The pill called Preven contains the hormones estrogen and progestin. The pill called Plan B contains only progestin.

The U.S. Food and Drug Administration also has said that 13 brands of regular birth control pills are safe for emergency use. The number of pills you take in each dose depends on which brand of pills you are using. To learn more about which pills are safe for emergency use, visit

An IUD that is placed in your womb within five days of unprotected sex also can prevent pregnancy. An IUD is a small device that can be left in your womb for up to 10 years. It will protect you from pregnancy during that time.

How does emergency birth control work?

Emergency birth control works differently depending on which day of your period cycle you start using it. It can stop your ovaries from releasing an egg, stop the egg from being fertilized by sperm, or stop the fertilized egg from attaching itself to the wall of the uterus.

No studies have shown that taking hormones while you are pregnant can hurt your baby. But, if you know you are pregnant, you should not take emergency birth control pills.

Are there any side effects?

Some women feel sick to their stomach after they take emergency birth control pills. This feeling should go away in about two days. Your doctor can give you medicine that may help you feel better.

Progestin-only pills may not make you feel as sick as pills containing estrogen and progestin. If you throw up within one hour of taking the pills, you may need to take another dose. Talk to your doctor.

A possible side effect of an IUD is bleeding between periods. Talk to your doctor to find out more about how IUDs work.

Who can use emergency birth control?

If you can take regular birth control pills, you can most likely take emergency birth control pills. If you are pregnant, have breast cancer, or have had blood clots, you should not use emergency birth control pills.

You should not use an IUD if you have an STD (sexually transmitted disease) or if you have been raped. Talk to your doctor about other options.

When do I need to start taking my regular birth control again?

After you take emergency birth control pills, your period may come a little earlier or a little later than usual. Call your doctor if you do not get your period within 21 days of taking the pills.

If your regular form of birth control is condoms, spermicides, or a diaphragm, you may go back to using it right away after taking emergency birth control pills.

If your regular form of birth control is the pill, shot, patch, or ring, talk to your doctor about when to start using it again.

Where can I get emergency birth control?

Talk to your doctor about how to get emergency birth control, or about having a prescription on hand in case you need it. You also may be able to get emergency birth control from university and women’s health centers, health departments, Planned Parenthood centers, and hospital emergency departments.

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