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Patient education: Emergency contraception (morning after pill) (Beyond the Basics)

Andrew M Kaunitz, MD
Section Editor
Robert L Barbieri, MD
Deputy Editor
Kristen Eckler, MD, FACOG
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Women who forget to take their birth control pills, have a condom break during intercourse, or have unprotected sex for other reasons (including victims of sexual assault) have a back-up method of protecting against pregnancy. This is called "emergency contraception" and goes by several other names, including "postcoital contraception," "the morning after pill," and "Plan B," which is the brand name of one of the medications used for emergency contraception. Using emergency contraception should not be confused with taking medicine to induce an abortion, which is a very different medication and process.

Emergency contraception is a method of birth control to be used occasionally, in specific emergency situations, not as a primary form of birth control. Other forms of birth control are discussed separately.

(See "Patient education: Barrier methods of birth control (Beyond the Basics)".)

(See "Patient education: Hormonal methods of birth control (Beyond the Basics)".)

(See "Patient education: Long-term methods of birth control (Beyond the Basics)".)

(See "Patient education: Permanent sterilization procedures for women (Beyond the Basics)".)

(See "Patient education: Vasectomy (Beyond the Basics)".)


Any woman who has had unprotected sex for any reason can use emergency contraception. This includes women who have been raped. (See "Patient education: Care after sexual assault (Beyond the Basics)".)

Below are the different circumstances in which you might need emergency contraception:

If you had unprotected vaginal intercourse any time within the last five days (120 hours).

If you used your regular method of birth control incorrectly (and had intercourse), or if your regular method of birth control might have failed (and you had intercourse) within the last five days (120 hours). Reasons why a regular method of birth control could fail include:

A condom breaks, slips off, or is not used the whole time a couple is having sex

A woman who normally takes birth control pills containing both estrogen and progestin forgets to take her birth control pills two days in a row

A woman who normally takes birth control pills containing just progestin (called the "minipill") takes her pill more than three hours late

A woman who normally uses injections of depot-medroxyprogesterone acetate (also called Depo-Provera; Depo-Provera Contraceptive; depo-subQ Provera 104; and Provera) is more than two weeks late for her injection (some providers recommend emergency contraception if the woman is more than four weeks late for her injection)

A diaphragm or cervical cap moves, breaks, tears, or is removed too soon

A birth control skin patch comes off, is removed too early, or is put on too late

A birth control vaginal ring comes out, is removed too early, or is inserted too late

A man fails to "pull out" or withdraw in time and comes or ejaculates either inside the woman or on her genitals

A sperm-killing tablet or film fails to melt before sexual intercourse

A woman who uses the rhythm method makes a mistake figuring out the "safe time" in her cycle, or she has intercourse during the days she is likely to conceive

An intrauterine device (IUD) accidentally comes out

Is emergency contraception safe? — The pills used in hormonal emergency contraception contain the same hormones found in hormonal birth control methods (birth control pills, skin patches, vaginal rings, and one type of intrauterine contraceptive device). These hormones have been used safely for years.

Even women who cannot use estrogen-containing hormonal birth control as their primary method of contraception (such as those with a history of heart attack, stroke, clotting disorders, migraine headaches, or liver disease, or who are breastfeeding) can use emergency contraception because the hormones are taken for only one day.

Some types of emergency contraception do not contain any hormones. These types are the copper intrauterine device (IUD) and a product, ulipristal acetate, which is sold under the brand names ella or ellaOne.


Researchers are not certain how emergency contraception works, but they do know that it probably works differently depending on where a woman is in her cycle. It also depends on the type of emergency contraception that she uses. Most of the time, emergency contraception works by reducing the chance that the egg will be fertilized by sperm; intrauterine devices (IUDs) and ella may also reduce the chance that a fertilized egg will implant and begin a pregnancy.

However it works, one thing is clear: hormonal or intrauterine emergency contraception cannot reverse a pregnancy that has already happened. In other words, if a fertilized egg has already implanted itself in the uterus, emergency contraception will not interfere with the pregnancy or harm the baby. Hormonal or intrauterine emergency contraception is not the same as the "abortion pill", which contains very different medications.


There are two main types of emergency contraception, each of which is discussed below.  

Oral emergency contraception — Oral emergency contraception involves the use of pills that contain hormones or interfere with hormones.

There are two different regimens of hormone pills, based on the hormones they contain:

The most common regimen contains a form of the hormone progesterone called levonorgestrel.

The other is a combination regimen containing forms of two hormones: progesterone and estrogen. Pills in this regimen are really just the pills used in oral contraception, but you must take more than one for them to work as emergency contraception.

The levonorgestrel regimen is slightly more effective than the combination estrogen-progesterone pills, and less likely to cause nausea and vomiting, the most common side effect of pills used for emergency contraception (see 'Side effects of emergency contraception' below).

Levonorgestrel is available in the United States in two different formulations. The brand name for the single-dose regimen is Plan B One-Step, but generic versions are also available. The brand name for the two-dose regimen is Plan B, and it also has generic equivalents.

Even though levonorgestrel has advantages over estrogen-progesterone, some women find the combination regimen is easier to find. The combination estrogen-progesterone regimen is available by using many commonly prescribed birth control pills in different doses (table 1). Birth control pills require a prescription.

Ulipristal acetate (ella, ellaOne) is another form of oral emergency contraception. This pill works by preventing the hormone progesterone from having its normal effect on ovulation and the inside of the uterus. It is not a hormone.

Copper IUD for emergency contraception — An intrauterine device (IUD) can also be used for emergency contraception. The copper IUD is a plastic and copper device that must be inserted into the uterus by a healthcare provider. It is much more effective at preventing pregnancy than the pill methods, but requires an office visit, is more costly in the short-term, and is usually used by women who want to keep the IUD as an ongoing method of birth control. (See "Patient education: Long-term methods of birth control (Beyond the Basics)".)


There are a lot of factors that affect how well emergency contraception will work, including where a woman is in her cycle, how soon after unprotected sex the woman takes emergency contraception, what type of emergency contraception she uses, and her weight.

A woman in her mid-twenties who has sex one to two days before she ovulates, when she is most fertile, has about a one in three chance of getting pregnant without contraception. Meanwhile, a woman of the same age who has sex one to two days after she ovulates has a near zero chance of getting pregnant. This makes it hard to give concrete numbers to indicate how effective emergency contraception is. Overall, using emergency contraception reduces the chance of pregnancy by at least 50 percent. Of the different methods, the copper IUD is the most effective. After unprotected sex, the chance of pregnancy is less than 1 in 500 in women who have a copper IUD placed.

Emergency contraceptive pills less effective in overweight women — Studies indicate that emergency contraceptive pills, including both levonorgestrel and ulipristal acetate pills, may not work as well in overweight or obese women as they do in normal weight women. For this reason, women who weigh 165 pounds (75 kilograms) or more may want to consider a copper IUD instead of emergency contraceptive pills if they need emergency contraception. The copper IUD works well in woman of any weight. If an overweight woman chooses to use oral emergency contraception, ulipristal seems to be more effective than levonorgestrel.


Levonorgestrel — In the United States, Plan B One-Step is available on store shelves without a prescription for anyone to purchase without age restrictions. Generic single-dose (1.5 mg) tablets of levonorgestrel and brand and generic two-dose (0.75 mg) tablets of levonorgestrel are also available, but the rules addressing the age and prescription requirements for these are in flux. Some versions may require a prescription, others may be sold only to people who can prove they are at least 17 years of age. Also, the labels for some for these formulations may specify that levonorgestrel emergency contraception is for use in women 17 years of age and older. Despite what these labels say, studies show that levonorgestrel can be used safely and effectively for emergency contraception in women younger than 17 years of age.

Get it before you need it — Even though emergency contraception may be available without a prescription, it is not always easy to get to a pharmacy when you need to take the pills. What’s more, not all pharmacies carry the medications or make them easily available on the shelf. As a result, healthcare providers recommend that women who are having sex get the pills needed for emergency contraception ahead of time, before they need them, and keep them at home. That is important because the pills are most effective when they are used shortly after unprotected sex. If you would like to buy some emergency contraception, call Planned Parenthood or your local pharmacy to find out if you can get it there. If cost is a concern, ask if you can get a generic version.

Other forms of emergency contraception — Ulipristal (brand names: ella, ellaOne) and standard birth control pills (estrogen and a progestin) require a prescription, regardless of age. The copper intrauterine device (IUD) must be inserted by a healthcare provider.


You do not need to have a physical exam or any lab tests to take nonprescription emergency contraception. However, if you need emergency contraception because you were raped, you should seek the help of a counselor or other healthcare professional. Your doctor should rule out pregnancy by history, physical exam, and/or laboratory testing before giving you a prescription for ulipristal for emergency contraception (nonhormonal emergency contraception). (See "Patient education: Care after sexual assault (Beyond the Basics)".)

Timing — You can take emergency contraceptive pills any time during your menstrual cycle. It does not matter when you had your last period.

Both the levonorgestrel pills and estrogen-progesterone pills are most effective when taken as soon as possible after unprotected sex. You can take them up to 120 hours (5 days) after sex, although the treatment become less effective as more time goes by.

Ulipristal acetate is effective up to 120 hours (five days) after unprotected sex.

The intrauterine device (IUD) can also be inserted up to 120 hours (five days) after unprotected sex.

Emergency contraception medication and dose

Levonorgestrel — Levonorgestrel is available in the United States as Plan B, which contains two 0.75 mg tablets to be taken 12 hours apart. However, many healthcare providers suggest taking the two tablets together, rather than 12 hours apart, because it is more convenient, works as well as taking the two pills separately, and is not harmful. Alternately, you can take Plan B One-Step, My Way, or Next Choice One Dose, which contains one 1.5 mg tablet that you take once.

Ulipristal acetate — Ulipristal acetate is available as ella or ellaOne, which consists of a single 30 mg tablet.

Estrogen-progesterone pills — No estrogen-progesterone pill is available in pill packets specifically for emergency contraception. However many birth control pills contain these two hormones. The table provides information on which birth control pills you can take as emergency contraception, and how many pills to take for each dose (table 1).

Copper IUD — The best way to prevent pregnancy is to have a copper IUD inserted. This makes the most sense if you would like to leave the IUD in place and use it as your ongoing method of birth control, or if you are obese. Copper IUDs are discussed in detail separately. (See "Patient education: Long-term methods of birth control (Beyond the Basics)".)

Side effects of emergency contraception — Nausea and vomiting are the most common side effects of the emergency contraceptive pills. These side effects are more common with the combination regimen using pills that contain both estrogen and levonorgestrel than those that contain levonorgestrel alone. Emergency contraception is very safe, which is why some types are now available without a prescription.

The table shows the percentages of women who experience nausea and vomiting, depending on which type of emergency contraception they take (table 2).

Side effects for ulipristal acetate are similar to those for levonorgestrel.

The copper IUD sometimes causes heavier periods. This often gets better with time.

Preventing nausea and vomiting — If you are worried about developing nausea and vomiting, you can take a medication to prevent these side effects.

Meclizine is a non-prescription medication that helps prevent nausea and vomiting; it is sold under the brand names Antivert, Bonine, Dramamine, and Medi-Meclizine. It is important to follow the dosing instructions on the box or bottle.

Metoclopramide (Reglan) is another medication that helps prevent nausea and vomiting, but you'll need to get a prescription for it from your healthcare provider.

What to do if you vomit — If you vomit within an hour after taking levonorgestrel pills, you should take medication for nausea and vomiting and then take then another full dose of levonorgestrel.

If you vomit within an hour of taking oral contraception pills (estrogen-progesterone pills), you have two choices:

You can either take medication to prevent nausea and vomiting and take the full dose of oral contraceptive pills (estrogen-progesterone pills) again; or

You can switch to levonorgestrel pills in the hopes that they will not cause the same side effects as the combination pills.


If you take emergency contraception, you will need to use some form of birth control until you get your period. You can still get pregnant if you have unprotected sex again after you take emergency contraception.

If you normally use birth control pills, a patch, or a vaginal ring, but you missed some doses, you should resume those methods the day following your emergency contraception, although you will need to use a backup form of birth control (such as a condom) for at least seven days. However, if you took ulipristal, and you normally use birth control pills, wait at least five days before starting your regular pills again. This is because ulipristal can interfere with the way birth control pills work. Even after you start taking your pills again, you should still use a condom every time you have sex until your next period. (See "Patient education: Hormonal methods of birth control (Beyond the Basics)".)

If you normally use condoms, a diaphragm, or a cervical cap, go back to using those methods right away. (See "Patient education: Barrier methods of birth control (Beyond the Basics)".)

If you have unprotected sex again, you can take emergency contraception again.


Your period should come within a week of when it normally comes. Some women have their period a little sooner than expected; others have it a little later than expected. However, if you do not get your period within three or four weeks of taking emergency contraception, you should have a pregnancy test, either at home or in a medical office.

If your pregnancy test is negative, wait for your menstrual period for one more week. If you still have not had a menstrual period by this time, call your doctor or nurse for further instructions.

If you are using a hormonal method of birth control (pill, skin patch, vaginal ring, injection), be sure to take the next dose (or apply a new patch or insert a new ring) on schedule, even if you have not had your menstrual period. Call you healthcare provider for further instructions.

In addition, call your doctor or nurse if you develop stomach pain or unexpected vaginal bleeding.


Emergency contraception is appropriate for any woman who has had recent unprotected sex for any reason. This includes women who have been raped, and women whose normal method of birth control may have failed.

Women who can't take birth control pills for routine contraception because of medical conditions such as migraine or history of blood clots in the leg or lung can safely take emergency contraception.

A woman does not need a physical exam or any lab tests to get emergency contraception.

Women who need emergency contraception should take it as soon as possible after unprotected sex. Emergency contraception is most effective within the first day of unprotected sex, but it can work up to five days (120 hours) later. Women can take emergency contraception at any time during their menstrual cycle.

The most effective emergency contraceptive is the copper intrauterine device (IUD), and therefore it is the preferred method of emergency contraception. It also has the advantage of ongoing contraception.

For women who prefer to take a pill, doctors recommend levonorgestrel pills rather than estrogen-progesterone pills because they are more effective and cause less nausea and vomiting. Doctors also recommend taking levonorgestrel as a single dose of 1.5 mg (2 pills at the same time) rather than as one dose of 0.75 mg followed by a second dose of 0.75 mg 12 hours later (even though that is what the label Plan B recommends). Plan B One-Step, My Way, and Next Choice One Dose come as a single 1.5 mg pill. Ulipristal acetate, where available, can be taken instead of levonorgestrel pills, and may be more effective than levonorgestrel pills for women 72 to 120 hours after unprotected intercourse.

Women who weigh 165 pounds (75 kilograms) or more may want to consider a copper IUD for emergency contraception because pills may be less effective.

Women who use emergency contraception do not need to see a healthcare provider after taking it. However, they should have a pregnancy test if their period does not occur within three or four weeks, or if they develop unusual vaginal bleeding or abdominal pain.

Women can still get pregnant if they have unprotected sexual intercourse again after taking emergency contraception pills. If necessary, they can repeat a course of emergency contraception, but a much more effective way to prevent pregnancy is to consistently use normal birth control methods.

It's a good idea for women to have a supply of emergency contraction available at home "just in case."


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Emergency contraception (The Basics)
Patient education: Care after rape or sexual assault (The Basics)
Patient education: Hormonal birth control (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Barrier methods of birth control (Beyond the Basics)
Patient education: Hormonal methods of birth control (Beyond the Basics)
Patient education: Long-term methods of birth control (Beyond the Basics)
Patient education: Permanent sterilization procedures for women (Beyond the Basics)
Patient education: Vasectomy (Beyond the Basics)
Patient education: Care after sexual assault (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Intrauterine contraception: Devices, candidates, and selection
Contraception: Overview of issues specific to adolescents
Emergency contraception
Evaluation and management of adult sexual assault victims

The following organizations also provide reliable health information.

National Library of Medicine


National Institute of Child Health and Human Development (NICHD)

     Toll-free: (800) 370-2943

National Women's Health Resource Center (NWHRC)

     Toll-free: (877) 986-9472

Planned Parenthood Federation of America

     Phone: (212) 541-7800

The Hormone Foundation


The Emergency Contraception Website, Princeton University



Literature review current through: Sep 2016. | This topic last updated: Apr 21, 2015.
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