A stressful moment after unprotected sex or a birth control slip can leave you wondering what to do next. Understanding what emergency contraception is, how it works, and how to use it safely can give you back a sense of control.
In this guide, you will learn what emergency contraception is, the types available, how effective they are, and what to expect if you decide to use it.
Understand what emergency contraception is
Emergency contraception is any method you use after sex to reduce your chance of getting pregnant. It is a backup plan for situations like:
- You had sex without any birth control
- A condom broke or slipped
- You missed pills, patches, or rings
- You were forced to have sex and did not consent
Emergency contraception does not protect you from sexually transmitted infections (STIs), including HIV. For STI protection, you still need condoms or other prevention methods such as PrEP, as the Centers for Disease Control and Prevention (CDC) notes (CDC).
You can use emergency contraception within 5 days of unprotected sex, but every major health organization agrees that the sooner you take it, the better it works (WHO).
Know the main types of emergency contraception
When you ask “what is emergency contraception,” you are really asking about a few different options that work in different ways. As of 2024 in the United States, there are four main methods (CDC).
1. Copper IUD (intrauterine device)
The copper IUD is a small, T-shaped device that a health care provider places in your uterus. It is the most effective form of emergency contraception, with effectiveness over 99 percent when inserted within 5 days of unprotected sex (WHO).
According to the American College of Obstetricians and Gynecologists (ACOG), the copper IUD works mainly by preventing sperm from fertilizing an egg. It can stay in place as a highly effective birth control method for up to 10 years, and you can ask to have it removed at any time (ACOG).
2. Ulipristal acetate pill
Ulipristal acetate is a prescription-only emergency contraceptive pill, often sold under brand names like ella. It changes how progesterone works in your body and delays or prevents ovulation, which means an egg is not released for sperm to fertilize (ACOG).
Ulipristal pills:
- Can be taken up to 5 days (120 hours) after unprotected sex
- Do not lose effectiveness during that 5 day window (ACOG)
- Are more effective than levonorgestrel pills if you are between 3 and 5 days after sex (CDC)
Because a prescription is required, you may need to call your provider, an urgent care clinic, or a telehealth service quickly if you want this option.
3. Levonorgestrel pill
Levonorgestrel emergency contraception is often what people mean when they say “the morning after pill.” It contains a progestin hormone and is available without a prescription in the United States, so you can usually buy it directly from a pharmacy shelf (Cleveland Clinic).
Key points about levonorgestrel pills:
- Work best within 72 hours (3 days) after unprotected sex
- Can be taken up to 5 days, but effectiveness drops over time (Mayo Clinic)
- Mainly prevent or delay ovulation, so no egg is released (Mayo Clinic)
The CDC notes that levonorgestrel and ulipristal are similarly effective in the first 3 days, but ulipristal works better if you are closer to the 5 day mark (CDC).
4. Combined estrogen and progestin pills
Some regular birth control pill packs can be used in specific doses as emergency contraception. This is called a combined regimen and includes both estrogen and progestin.
However, the CDC states that this combined method is less effective and causes more side effects, especially nausea and vomiting, compared with dedicated pills like ulipristal or levonorgestrel (CDC). Because of that, it is usually considered a backup option when other forms are not available.
Learn how emergency contraception works in your body
All modern emergency contraception methods work by preventing pregnancy from starting. They do not end an existing pregnancy and they do not cause abortion, a point highlighted by the World Health Organization (WHO) and several medical bodies (WHO).
Here is what is happening in your body:
- Emergency contraceptive pills (levonorgestrel and ulipristal) mainly delay or block ovulation, so there is no egg available for sperm to fertilize (WHO)
- The copper IUD releases copper ions that are toxic to sperm and prevent fertilization before sperm and egg meet (WHO)
Once an embryo has implanted in the uterus, emergency contraception cannot disrupt it and will not harm a developing embryo (WHO).
Compare effectiveness and timing
Timing is one of the most important pieces of emergency contraception. The same method can be very effective if you use it early and less helpful if you wait.
| Method | When you can use it | Overall effectiveness |
|---|---|---|
| Copper IUD | Within 5 days after sex | Over 99% effective (WHO) |
| Ulipristal pill | Within 5 days after sex | Most effective pill, no drop off over 5 days (ACOG) |
| Levonorgestrel pill | Best within 72 hours, up to 5 days | Effective, but less so each day you wait (Mayo Clinic) |
| Combined pill regimen | Within 5 days after sex | Less effective, more side effects (CDC) |
If you have a higher body weight or BMI, pills may not work as well. ACOG notes that overweight or obesity can reduce the effectiveness of emergency contraceptive pills, and in that case the copper IUD is recommended as the most reliable option (ACOG).
Know who can use emergency contraception
According to WHO, any woman or girl of reproductive age can use emergency contraception. There are no absolute medical contraindications and no minimum age limit for emergency contraceptive pills (WHO).
To use a copper IUD, you still need to meet the usual medical criteria for IUD insertion. Your provider will review your health history and do a pelvic exam before placing one.
Emergency contraception is meant for occasional use, when something goes wrong or you did not plan to have sex. It is not designed to replace a regular birth control method, something both the Cleveland Clinic and Mayo Clinic emphasize (Cleveland Clinic, Mayo Clinic).
Understand side effects and safety
Emergency contraception is considered safe, even if you use it more than once. It does not affect your future fertility and does not increase your risk of birth defects if you happen to get pregnant later (Cleveland Clinic).
You might notice short term side effects, especially with pills:
- Nausea or upset stomach
- Headache or dizziness
- Breast tenderness
- Fatigue
- Mild abdominal pain
- Light spotting or changes in your next period
ACOG notes that these side effects are usually mild and go away on their own (ACOG). Your next period may come a little earlier or later than usual. Mayo Clinic explains that your period can be delayed by up to one week after taking the morning after pill. If you do not get your period within 3 weeks, you should take a pregnancy test (Mayo Clinic).
If you have a copper IUD inserted, you might feel cramping during and shortly after the procedure. Some people also notice heavier or more painful periods, especially in the first few months.
Decide which option fits your situation
When you are choosing an emergency contraception method, think about your timing, access, and long term needs.
If you want to prevent pregnancy and also get a long acting method, the copper IUD is usually the best fit. It works extremely well as emergency contraception and then keeps working as your regular birth control for years (ACOG).
If you prefer a pill and you are within 5 days of unprotected sex, a prescription for ulipristal gives you the strongest pill option, especially if it has already been a few days (ACOG, CDC).
If you need something quickly and do not have easy access to a doctor, an over the counter levonorgestrel pill is available at most pharmacies without a prescription (Cleveland Clinic). Take it as soon as you can.
If you only have access to combined birth control pills and no dedicated emergency contraception, you can talk to a clinician or pharmacist about using a combined regimen. Just know that it may cause more nausea and is less effective than the other methods (CDC).
Use emergency contraception as part of a bigger plan
Emergency contraception is a powerful backup, but it is not meant to be your main form of birth control. Regular methods like IUDs, implants, pills, patches, rings, condoms, or injections are more effective and less stressful over time.
After you use emergency contraception, it can help to:
- Schedule a follow up with a health care provider to talk about ongoing birth control options
- Get tested for STIs if there is any risk, since EC does not protect against infections (CDC)
- Take a pregnancy test if your period is more than a week late or does not come within 3 weeks (Mayo Clinic)
Knowing what emergency contraception is, how it works, and when to use it can make a frightening moment feel more manageable. You deserve information that is clear and tools that help you protect your health, so you can make choices that align with your life and your plans.
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