What is emergency contraception?
Emergency contraception is a way to prevent pregnancy if:
- You had sex without using birth control.
- Your birth control method failed. Maybe you forgot to take your pill or get your shot, the condom broke or came off, or your diaphragm slipped.
- You were sexually assaulted. Even if you were using birth control, emergency contraception can help decrease your chance of getting pregnant.
If you had sex without birth control, there is a chance that you could get pregnant. This is true even if you have not started having periods yet or you are getting close to menopause. You could also get pregnant if you used a birth control method that is not very reliable or if you didn't use it the right way.
Using emergency contraception right away can prevent an unwanted pregnancy and keep you from worrying while you wait for your next period to start.
What are the types of emergency contraception?
There are two main types of emergency contraception: pills and the copper intrauterine device (IUD). Most women choose pills because they work well, don't cost a lot, and are usually easy to get. The IUD works very well, but it has to be inserted by a doctor.
- Emergency contraception pills: Pills used for emergency contraception are sometimes called "morning-after pills." They can be used up to 5 days after unprotected sex.
- The most common option contains a progestin hormone called levonorgestrel. Progestin is a synthetic version of the hormone progesterone.
- Another option is a medicine called ulipristal acetate (for example, ella) that affects the progesterone in your body.
- Some birth control pills are also used. These often contain a combination of the hormones estrogen and progestin. If you already take birth control pills, you may be able to use the pills you have as emergency contraception. Talk to your doctor or check the websites listed below for the correct doses.
- IUD: The copper IUD is a small, T-shaped plastic device that is inserted into your uterus. It can be placed up to 5 days after unprotected sex to prevent pregnancy. (Note: The hormonal IUD, such as the Mirena, is not used for emergency contraception.)
How does it work?
Emergency contraception pills work by preventing ovulation.
Emergency contraception hormones may prevent fertilization by stopping the ovary from releasing an egg (ovum). They also make the fallopian tubes less likely to move an egg toward the uterus. Emergency contraception is also thought to thin the lining of the uterus, or endometrium. The thickened endometrium is where a fertilized egg would normally implant and grow.
The copper IUD for emergency contraception may prevent fertilization or implantation.
Where can you get emergency contraception?
Emergency contraception. You can get emergency contraception without a prescription at most drugstores.
Some types of emergency contraception, such as ulipristal acetate (for example, ella) are available only with a prescription from a doctor.
Birth control pills. If you already have birth control pills on hand, you may be able to use them for emergency birth control. To find out which brands of pills work and how to take them, go to www.plannedparenthood.org or https://ec.princeton.edu for emergency contraception information.
Some pharmacists will not sell emergency contraception or fill prescriptions for birth control pills. If this happens to you, ask for the location of a pharmacist who will, or go to or call the Planned Parenthood clinic nearest you.
IUD. You can get an IUD from many doctors, from college and public health clinics, or in most hospital emergency rooms. An IUD has to be inserted by a doctor or other health professional.
How do you use it?
Emergency contraception pills
The pills come in 1-pill or 2-pill packages. Follow the directions in the package or take them as your doctor directs you to.
You can take emergency contraception up to 5 days after unprotected sex.
Birth control pills as emergency contraception
For most regular birth control pills, you take one dose of 2 to 5 pills as soon as you can. Then you take a second dose 12 hours later. The dose depends on the type of pill.
If you use birth control pills for emergency contraception, keep the following in mind:
- Birth control pills can cause nausea. Take an antinausea medicine such as Dramamine with the first dose and again 1 hour before the second dose.
- If you vomit within 2 hours of taking the pills, call your doctor for advice. You may need to repeat the dose.
- Be sure you take the active hormone pills. In a 28-day pack, the first 21 pills contain hormones. The last 7 pills (the ones you take during your period) do not contain any hormones. If you use 21-day packs, all of the pills contain hormones.
A doctor or other health professional has to insert an IUD.
How well does it work?
The sooner you use emergency contraception, the more likely it is to prevent pregnancy. Overall:
- The copper IUD is the most effective form of emergency contraception. It is inserted by a doctor and can prevent almost all pregnancy.
- A prescription pill with ulipristal acetate (such as ella) works better for most woman to prevent pregnancy than the pill with levonorgestrel. If you have used hormonal birth control in the last week or have been using the shot, the prescription pill may not work well for you.
- Emergency contraceptive pills with levonorgestrel are not as effective as the copper IUD or ulipristal. But they are available without a prescription at most drugstores.
If you are overweight or obese, emergency contraception pills may not work as well to prevent a pregnancy. Talk with your doctor about methods that aren't affected by your weight, such as the copper IUD.
If you haven't started your period within 3 weeks after using emergency contraception, get a pregnancy test.
Does it cause side effects?
Emergency contraception may cause some side effects.
- Emergency contraception may cause spotting or mild symptoms like those of birth control pills. It usually doesn't cause nausea.
- Birth control pills can cause nausea or vomiting. In some women, they can also cause sore breasts, fatigue, headache, belly pain, or dizziness.
- An IUD may cause cramping and bleeding during the first few days after insertion.
Call your doctor if you have a headache, dizziness, or belly pain that is severe or that lasts longer than 1 week.
If you are already pregnant, most pills won't harm the fetus. But some pills, such as ulipristal, may cause problems with the pregnancy. More research is needed to know for sure. An IUD could cause problems with the pregnancy.
What else should you think about?
- Emergency contraception pills won't protect you for the rest of your cycle. Use condoms or another barrier method of birth control until you start your period. If you usually use a hormonal method of birth control, such as birth control pills, the vaginal ring, or the patch, check with your doctor about when to start using them again.
- If you are overweight or obese, emergency contraception pills may not work as well to prevent a pregnancy. Talk with your doctor about methods of emergency contraception that aren't affected by a woman's weight, such as the copper IUD.
- Unless you get an IUD, emergency contraception does not take the place of regular birth control. Find a good method of birth control you can use every time you have sex.
- Emergency contraception does not prevent sexually transmitted infections (STIs). If you are worried you might have been exposed to an STI, talk to your doctor.
- Accidents can happen. It is a good idea to keep a set of the pills on hand in case you ever need it.
Other Works Consulted
- Stewart F, et al. (2007). Emergency contraception. In RA Hatcher et al., eds., Contraceptive Technology, 19th ed., pp. 87–112. New York: Ardent Media.
Current as of: February 11, 2020
Author: Healthwise Staff
Sarah Marshall MD - Family Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine