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Plan B

Generic name: Levonorgestrel

Drug Information

Medically reviewed by Jessica Swirble, PharmD
Last updated on 5/24/2024

Drug Information | Side Effects | Use & Dosage | Request a Prescription

Quick facts:
  • Brand Name: Plan B
  • Generic Name: Levonorgestrel
  • Uses: Emergency contraception to prevent pregnancy after unprotected sex or birth control failure
  • Drug Class: Progestin
  • Availability: Over-the-counter
  • Generic Status: Yes
  • Controlled Substance: No

What is Plan B?

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.

What is Plan B used for?

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.

How does Plan B work?

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.

How do I take Plan B?

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.

How long does it take for Plan B to work?

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.

Are there any other uses for Plan B?

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.

Dosage forms of Plan B

Plan B is available in the following dosage form:

  • Oral tablet: Levonorgestrel tablet

Plan B is available over the counter. You do not need a prescription from a healthcare provider to obtain this medication.