The morning-after pill: What is emergency contraception?

Emergency contraceptive pills approved by the Food and Drug Administration (FDA) have been used for more than 25 years by millions of women.^1,2,3,4,5 These medications use synthetic versions of the body’s natural hormones to help prevent a pregnancy from happening after unprotected sex.⁶

Emergency contraception is an option to consider depending on individual needs and health situations. Emergency contraception is available over the counter at local pharmacies. It can also be prescribed by a provider. Always read product labels and consult a health care provider to discuss contraception options.

In this article:

• What is the morning-after pill?
• How does the morning-after pill work?
• What are the side effects of the morning-after pill?
• How often can someone use emergency contraception?
• Other types of emergency contraception

What is the morning-after pill?

Despite its “morning-after” nickname, emergency contraception should be taken as soon after unprotected sex as possible. It is effective if taken within three days of unprotected sex.  There are two formulations of emergency contraction. Depending on how soon they are taken after unprotected sex, they differ in how effective they are in preventing pregnancy. Neither is effective if you are already pregnant.^7,8,9,10

There are two types of morning-after pills:

• Levonorgestrel pills contain only a progestin, a synthetic form of the hormone progesterone. It can be bought at drugstores without a prescription, as a generic or under brand names like Aftera, Julie and Plan B.¹¹ It protects best if taken as soon as possible within three days.^12,13 Remember to consult product labels and use as directed.
• Ulipristal acetate pills are the most effective emergency contraceptive in oral form.¹⁴ Available only with a prescription, one pill can be taken up to five days after unprotected sex.¹⁵ However, it is more effective the sooner it is taken.¹⁶

How does the morning-after pill work?

Levonorgestrel works by temporarily stopping or delaying ovulation, preventing the ovaries from releasing eggs for sperm to fertilize.¹⁷ Ulipristal acts the same way and may also thin the lining of the uterus to reduce the chance that an egg implants in the womb.¹⁸ Note that these medications will not abort an already established pregnancy (i.e., if the egg has already been fertilized).^19,20,21

What are side effects of the morning-after pill?

Common side effects associated with emergency contraception pills include the following: 

• Abdominal pain
• Breast pain^22,23
• Dizziness
• Headache
• Nausea
• Tiredness

After a person takes the pill, their next period may come early or late or they may have light bleeding in between.²⁴

In any case, read the package labeling carefully. It’s also important to talk with a health care provider if side effects continue or if someone hasn’t gotten their period within three weeks after taking the morning-after pill.²⁵

If a person vomits within two hours after taking the levonorgestrel pill, their doctor may recommend another dose.²⁶ Ulipristal acetate may require another dose if vomiting occurs within three hours. It may help to take an anti-nausea medication 30 minutes before taking the pill again.^27,28,29

How often can someone use emergency contraception?

The morning-after pill should not take the place of traditional pills or other birth control methods, which are more effective at preventing pregnancy.^30,31,32 It is also not recommended to use repeatedly as a replacement for other types of contraception. Repeated use may increase side effects and cause irregular periods. It also costs more and may be less convenient than other birth control methods.^33,34

If someone wants to start or resume taking typical birth control pills, they can do that any time after taking emergency contraception. They must also use a barrier method along with their regular birth control for seven days after starting their regular birth control method.³⁵

With ulipristal, wait five days after taking the pill before beginning regular birth control pills. Also use condoms or another barrier method until the next menstrual cycle begins in order to prevent pregnancy in the meantime.^36,37

Remember that emergency contraception does not protect against sexually transmitted infections (STIs). Condoms are an effective way to prevent STIs.

As always, anyone considering these options should check all package instructions for directions and warning information.

Other types of emergency contraception

Beyond an oral pill, a copper intrauterine device (IUD) is another option. It works by making sperm less able to fertilize the egg. It’s the most effective, lowering the risk of pregnancy to nearly zero.^38,39,40 A health care professional must insert the IUD within five days after unprotected sex. It can stay in place for up to 10 years or until a person is ready to try for a pregnancy.^41,42

This content is for informational purposes only and is not medical advice. Consult your health care provider before taking any vitamins or supplements and prior to beginning or changing any health care practices.