Originally published March 10, 2010. Updated October 6, 2026, to reflect current contraceptive options, effectiveness rates and terminology.
The morning-after pill is a form of emergency contraception that can help prevent pregnancy after unprotected sex or when a regular birth control method fails. You might consider emergency contraception if a condom breaks, you miss birth control pills, or you have sex without using contraception.
Despite its name, the morning-after pill does not have to be taken the morning after sex. Depending on the type, emergency contraceptive pills can be used for up to five days after unprotected sex, although taking them as soon as possible generally provides the best chance of preventing pregnancy.
How Does the Morning-After Pill Work?
Emergency contraceptive pills primarily work by preventing or delaying ovulation, so an egg is not available to be fertilized.
They do not end an existing pregnancy and are not the same as medication abortion.
Plan B One-Step and its generic equivalents contain levonorgestrel, a synthetic progestin also used in many regular birth control methods. Another emergency contraceptive pill, ella, contains ulipristal acetate.
How Long After Sex Can You Take the Morning-After Pill?
The sooner emergency contraception is used, the better.
Levonorgestrel emergency contraceptive pills, such as Plan B One-Step and generic versions, are intended to be taken as soon as possible after unprotected sex. FDA labeling recommends taking Plan B within 72 hours, although research shows levonorgestrel emergency contraception may still provide some protection for up to five days. Effectiveness decreases with time.
Ulipristal acetate, sold under the brand name ella, can be taken within five days (120 hours) after unprotected sex and tends to be more effective than levonorgestrel during days three through five.
A copper IUD can also be inserted by a healthcare professional within five days of unprotected sex and is one of the most effective forms of emergency contraception. It can then continue to provide ongoing birth control.
Types of Emergency Contraception
There are several emergency contraception options:
Levonorgestrel Pills
Plan B One-Step and generic equivalents contain levonorgestrel. In the United States, these pills are available over the counter without an age restriction or prescription.
Ulipristal Acetate
Ulipristal acetate, sold as ella, is another emergency contraceptive pill. It requires a prescription in the United States and can be taken for up to five days after unprotected sex.
Copper IUD
A copper IUD can be inserted within five days of unprotected sex and provides highly effective emergency contraception as well as long-term pregnancy prevention.
Certain combined birth control pills can also be used as emergency contraception using a specific dosing regimen, but this method is less effective and more likely to cause nausea and vomiting than levonorgestrel or ulipristal. Talk to a healthcare professional before using regular birth control pills this way.
What Are the Side Effects of the Morning-After Pill?
Emergency contraceptive pills are generally well tolerated, but temporary side effects can occur.
These may include:
- Nausea
- Headache
- Dizziness
- Fatigue
- Breast tenderness
- Abdominal discomfort
- Spotting or irregular bleeding
- Changes in the timing of your next period
Your next period may arrive earlier or later than expected.
If you vomit soon after taking an emergency contraceptive pill, contact a pharmacist or healthcare provider because another dose may be necessary.
Does Body Weight Affect the Morning-After Pill?
Body weight may affect how well some forms of emergency contraception work.
Research suggests that levonorgestrel emergency contraception may be less effective in women with obesity. Ulipristal acetate may be more effective than levonorgestrel for some women with a higher body weight, although effectiveness may also decrease with increasing weight.
A copper IUD remains a highly effective emergency contraception option regardless of body weight.
If you are unsure which option is best for you, a pharmacist or healthcare provider can help.
What Happens After You Take Emergency Contraception?
If you take a levonorgestrel emergency contraceptive such as Plan B, you can generally start or resume your regular hormonal birth control immediately. Use condoms or avoid sex for the next seven days while your regular contraception becomes effective.
The advice is different after taking ella. Because hormonal contraception may reduce the effectiveness of ulipristal acetate, the CDC recommends waiting at least five days before starting or restarting hormonal birth control. You should then use condoms or avoid sex for seven additional days after restarting your regular method.
Take a pregnancy test if you do not get your expected period or withdrawal bleed within about three weeks after using emergency contraception.
Is the Morning-After Pill the Same as the Abortion Pill?
No.
Emergency contraception works before pregnancy is established, primarily by delaying or preventing ovulation. It will not end an existing pregnancy.
Medication abortion is a different treatment involving different medications that are used after pregnancy has begun.
Can You Use the Morning-After Pill More Than Once?
Emergency contraceptive pills can be used when needed, including more than once if necessary. However, they are generally less effective than using a regular contraceptive method consistently and are not intended to replace ongoing birth control.
If you find yourself needing emergency contraception frequently, consider speaking with a healthcare provider about a regular contraceptive method that may be easier or more reliable for you.
The Bottom Line
The morning-after pill can reduce the chance of pregnancy after unprotected sex or birth control failure, but timing matters. Levonorgestrel pills such as Plan B work best when taken as soon as possible, while ella can be taken for up to five days and may be more effective later in that window.
A copper IUD is another highly effective emergency contraception option and can provide continued birth control afterward.
Emergency contraception does not cause abortion, does not terminate an existing pregnancy and does not protect against sexually transmitted infections.
