Yes. Plan B can be used after a contraceptive failure, such as a condom breaking or missed birth-control pills. It contains levonorgestrel, which helps prevent pregnancy mainly by delaying the release of an egg. Take it as soon as possible, ideally within 72 hours. It does not work every time, does not end an existing pregnancy, and does not protect against sex later in the cycle.
When Can Plan B Help After Birth Control Fails?
Plan B is an emergency contraceptive, often called a morning-after pill. It is designed to reduce the chance of pregnancy after unprotected sex or when a regular contraceptive method may not have worked. You do not need to wait for a missed period or pregnancy symptoms before considering emergency contraception.
Emergency contraception may be appropriate in situations such as:
- A condom breaks, slips off, or leaks during sex.
- Several birth-control pills are missed, or pills are taken incorrectly.
- A contraceptive method is not used according to its instructions, creating a risk of pregnancy.
- A vaginal contraceptive method is used incorrectly or a scheduled contraceptive dose is missed or delayed, depending on the method.
- Sex occurs without contraception, or the withdrawal method does not prevent semen from entering the vagina.
Whether emergency contraception is needed after a missed dose depends on the type of birth control, how long it was delayed, and when sex occurred. Checking the method's instructions or speaking with a pharmacist can help clarify the next step. When pregnancy prevention is a concern, do not delay seeking emergency contraception while trying to calculate the exact risk.
How Does Plan B Work After a Contraceptive Failure?
Plan B contains levonorgestrel, a hormone that helps prevent pregnancy by delaying or preventing ovulation, which is the release of an egg from an ovary. This delay may prevent sperm from meeting an egg. The pill works before pregnancy is established; it does not terminate an existing pregnancy.
According to the U.S. Food and Drug Administration (FDA), Plan B One-Step contains a single 1.5 mg dose of levonorgestrel and should be taken as soon as possible after unprotected sex or contraceptive failure. It may not prevent pregnancy if ovulation has already occurred, which is one reason emergency contraception cannot guarantee that pregnancy will be avoided.
How Soon Should You Take Plan B?
Timing matters. Take Plan B as soon as possible after a contraceptive failure rather than waiting until the next day or until a period is late. The FDA recommends using levonorgestrel emergency contraception within 72 hours, or three days, of unprotected sex. Taking it earlier gives it a better chance of working.
However, passing the 72-hour mark does not mean that every emergency contraception option is no longer available. The Centers for Disease Control and Prevention (CDC) states that emergency contraceptive pills should be taken as soon as possible within five days of unprotected sex. Levonorgestrel may still reduce pregnancy risk on days four and five, but it becomes less effective with time. If more than three days have passed, ask a healthcare professional promptly about the most suitable available option.
Is Plan B the Best Emergency Contraception Option?
Plan B is a convenient option for many people, particularly when it can be taken soon after a contraceptive failure. However, other methods may provide better protection in some circumstances, especially when several days have passed.
Ulipristal acetate
Ulipristal acetate is another emergency contraceptive pill that can be used within five days after unprotected sex. It is generally more effective than levonorgestrel during the third to fifth day after sex. It may be a useful alternative when more time has passed, although availability and prescription requirements depend on the country.
The copper intrauterine device (IUD)
A copper IUD is the most effective established emergency contraception option. A trained healthcare professional can usually insert it within five days of unprotected sex, and it can continue to provide birth control afterward. The American College of Obstetricians and Gynecologists (ACOG) identifies the copper IUD as the most effective emergency contraception method. It may be worth discussing if avoiding pregnancy is a high priority or if oral emergency contraception may be less suitable.
What if you have a higher body weight?
Some evidence suggests that levonorgestrel emergency contraception may be less effective in people with obesity. This does not mean you should avoid taking it or delay seeking help. A healthcare professional can discuss alternatives, including ulipristal acetate or a copper IUD, based on the time since sex, medical history, and local availability.
How Should You Take Plan B After a Birth-Control Problem?
Plan B One-Step is taken as a single 1.5 mg tablet by mouth. Follow the instructions on the package for the product you have, since brands and formulations can vary. Do not delay taking emergency contraception while waiting for a pregnancy test when recent unprotected sex has created a pregnancy risk.
If vomiting occurs within three hours of taking an emergency contraceptive pill, another dose is generally recommended as soon as possible under CDC guidance. Contact a pharmacist or healthcare professional promptly to confirm what to do and whether another dose is needed.
If you take regular hormonal birth control, you can generally continue or restart it immediately after levonorgestrel emergency contraception. Use condoms or avoid sex for the next seven days while your regular method becomes reliable again, following any method-specific instructions. The guidance is different after ulipristal acetate: hormonal contraception generally needs to be delayed for five days because taking the medicines too close together can reduce effectiveness.
What Should You Expect After Taking Plan B?
Most people do not experience serious problems after taking levonorgestrel emergency contraception. Short-term effects can include nausea, headache, tiredness, dizziness, breast tenderness, or abdominal discomfort. Spotting may occur, and the next period may arrive earlier or later than expected or differ from the usual flow.
According to Planned Parenthood, these changes in the next period can occur after taking Plan B. A change in bleeding does not, by itself, confirm whether the pill worked. If symptoms are persistent, worsening, or concerning, seek medical advice.
When Should You Take a Pregnancy Test?
Plan B reduces the chance of pregnancy but cannot eliminate it. Take a home pregnancy test about three weeks after the contraceptive failure or after taking emergency contraception, especially if you have not had your expected period. Testing too early can give a negative result before a pregnancy is detectable.
If your test is positive, contact a healthcare professional to discuss the next steps. Plan B does not end an existing pregnancy. Seek urgent medical assessment if you develop severe or persistent abdominal pain, particularly with fainting or unusual bleeding, because these symptoms need prompt evaluation.
Does Plan B Protect You During Sex Later in the Cycle?
No. Plan B is intended to address pregnancy risk from sex that has already occurred. It does not provide ongoing protection against pregnancy from later sexual activity. If unprotected sex happens again after taking the pill, another emergency contraception assessment may be needed.
Plan B also does not prevent sexually transmitted infections (STIs). If condom failure may have exposed you to an STI, consider seeking testing or advice about other time-sensitive prevention options. For ongoing pregnancy prevention, using a regular contraceptive method correctly and consistently is more reliable than depending on emergency contraception alone.