Medically reviewed by Jessica Swirble, PharmD
Last updated on April 18, 2025
Drug Information | Side Effects | Use & Dosage | Request an Online Prescription
Plan B is an emergency contraceptive tablet that prevents unwanted pregnancies after unprotected sex or contraceptive failure during sexual intercourse. Contraceptive failure may occur when a daily birth control pill is taken incorrectly, a condom isn’t used correctly, or a condom breaks during sex.
Plan B is an emergency contraceptive that prevents pregnancy after unprotected sexual intercourse or contraceptive failure during intercourse. It should not be used in place of regular birth control.
Plan B pills cannot terminate an existing pregnancy, nor will they provide any protection against sexually transmitted infections. It is strictly used as an emergency measure after unprotected sex or contraceptive failure.
Plan B contains levonorgestrel, which belongs to a classification of birth control medications known as progestins. Progestins contain a synthetic version of the naturally occurring hormone progesterone. The ovaries produce progesterone, which aids in regulating the female reproductive system. Progestins prevent ovulation (the ovaries releasing an egg for fertilization) and thicken cervical mucus, making it harder for sperm to reach an egg. If sperm cannot get to an egg for fertilization, pregnancy is nearly impossible. It also alters the endometrial lining so that implantation cannot occur.
Plan B works more effectively the sooner you take it after intercourse. It is most effective within 72 hours of unprotected intercourse or contraceptive failure.
Plan B tablets are a form of emergency contraception, not a daily birth control pill. This means that you will become fertile again several days after taking them. Once the sex hormones released by Plan B dissipate, the reproductive system will return to working normally. Because of this, you should not use these pills as a substitute for routine contraception. It is also important to note that progestin medications work on the body's reproductive system. They do not protect against sexually transmitted infections or diseases.
Plan B is available as an oral pill.
Plan B is supplied as a single dose that should be taken within 72 hours of unprotected sex. The sooner it is taken after unprotected sex, the more effective it is.
If you vomit within 2 hours after taking Plan B, call your healthcare provider. You may need to take a second dose of Plan B.
Plan B works immediately to prevent unplanned pregnancy.
If you vomit within 2 hours after taking Plan B, call your healthcare provider. You may need to take a second dose of Plan B.
It is recommended that you speak with your healthcare provider 3 weeks after taking Plan B to confirm that you are not pregnant. If your period is late by a week or more after taking Plan B, talk to your healthcare provider to determine if you are pregnant.
While Plan B is primarily used as emergency contraception to prevent pregnancy after unprotected sex or birth control failure, healthcare providers may prescribe it for other uses.
Discuss any alternative uses of Plan B with your healthcare provider.
Plan B is available in the following dosage form:
Plan B is available over the counter. You do not need a prescription from a healthcare provider to obtain this medication.
The use of Plan B can lead to various side effects in some individuals.
Common mild side effects of Plan B use include:
More severe side effects of Plan B use can include:
If you experience any severe or concerning side effects while taking Plan B, contact your healthcare provider right away. Ectopic pregnancies, in particular, are medical emergencies that require immediate attention. If you experience severe abdominal pain several weeks after taking Plan B, seek medical attention.
Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with Plan B. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with Plan B.
Tell your provider if you are taking these medications or supplements:
Do not use Plan B if you are pregnant, planning to become pregnant, or breastfeeding.
Take Plan B exactly as directed on the package or as prescribed by your healthcare provider. It is most effective when taken as soon as possible after unprotected sex or birth control failure.
Plan B may cause side effects such as nausea, fatigue, or headache, so monitor your health and report any severe or persistent symptoms to your doctor.
In case of a Plan B overdose, seek medical attention immediately. Symptoms of overdose may include severe nausea or vomiting, sudden abdominal pain, or extreme tiredness. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.
Plan B is available in the following form:
The typical dose of Plan B is a single tablet of 1.5 mg of levonorgestrel taken as soon as possible after unprotected sex or birth control failure. It is most effective when taken within 72 hours (3 days) but can be taken up to 120 hours (5 days) after.
The dosage does not vary. It is crucial to follow the instructions provided with the medication or as advised by your healthcare provider.
Plan B should be taken exactly as directed. Do not take more than the recommended dose without consulting your provider.
If you have any questions about your dosage or need further guidance, contact your healthcare provider or consider scheduling an online doctor appointment through a telehealth platform like Sesame.
If you do not take Plan B within the optimal 72-hour window, take it as soon as you can. While its effectiveness decreases over time, it still provides some level of protection up to 120 hours after unprotected sex.
Plan B is a single-dose medication, so there is no regular dosing schedule to follow.
Continue monitoring for signs of pregnancy and consider taking a pregnancy test if your period is late by more than a week or if you experience other signs of pregnancy. Consult with your healthcare provider for further advice or if you have any concerns about the effectiveness of the treatment.
Store Plan B at room temperature, away from excessive heat and moisture. Keep the packaging closed when not in use and ensure it is out of reach of children.
Do not use the medication beyond its expiration date. If you have any questions about storage, consult your healthcare provider or pharmacist for guidance.