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Plan B One-Step

Generic name: levonorgestrel emergency contraceptiveLEE-voe-nor-jes-trel ]
Dosage form: tablet (1.5 mg)
Drug class: Contraceptives

Medically reviewed by Melisa Puckey, BPharm. Last updated on May 16, 2023.

What is Plan B One-Step?

Plan B One-Step is a morning-after pill (emergency contraceptive pill) used to prevent pregnancy after unprotected sex or failure of other forms of birth control (such as condom breakage, or a missed dose of birth control pills). The Plan B pill works by temporarily delaying the release of an egg from the ovary (ovulation), so it helps to prevent pregnancy before it starts.  Plan B (levonorgestrel, 1.5 mg) should be taken within 72 hours of unprotected sex or birth control failure, and the sooner it is taken, the better it works. 

Any person, regardless of age or gender can purchase Plan B One-Step right off the shelf without a prescription or ID requirement at all major retailers in the U.S.

The Plan B pill is a backup method of preventing pregnancy and should not be used as a regular form of birth control. Talk with your doctor or healthcare professional about the many forms of birth control available.

How effective is Plan B?

In a clinical trial Plan B was effective at lowering the chance of becoming pregnant from 8% on average to 1.1%, after a single act of mid-cycle unprotected sex if it was taken correctly within 72 hours after unprotected sex. In a review of clinical trials Plan B was shown to have an efficiency rate of 89% when taken correctly, as directed.

What is the difference between Plan B and Plan B One-Step?


Do not use this medicine if you are already pregnant. Levonorgestrel will not terminate a pregnancy that has already begun (the fertilized egg has attached to the uterus).

Ask a doctor or pharmacist before taking levonorgestrel if you regularly use medication for seizures, tuberculosis, or HIV/AIDS. Certain medications can make levonorgestrel less effective as an emergency form of contraception.

Before taking this medicine

You should not use Plan B One-Step if you are allergic to levonorgestrel or any of the ingredients in this medicine. A list of all ingredients is near the bottom of this page.


Do not use this medicine if you are already pregnant. This medicine will not terminate a pregnancy that has already begun (the fertilized egg has attached to the uterus).


Levonorgestrel may slow breast milk production. Tell your doctor if you are breastfeeding.

How should I take Plan B One-Step?

Take Plan B One-Step exactly as directed on the label, or as prescribed by your doctor or health professional.

Plan B One-Step is one tablet that is taken once.  It must be taken as soon as possible and no later than 72 hours (3 days) after unprotected sex.  The sooner the tablet is taken, the better it works.

Call your doctor right away if you vomit within 2 hours after taking this medicine, as you may need to take another tablet.

Visit your doctor within 3 weeks after taking this medicine. A doctor should confirm that you are not pregnant and that this medicine has not caused any harmful effects.

If your period is late by 1 week or longer after the expected date, you may be pregnant. Get a pregnancy test and contact your doctor if you are pregnant. Levonorgestrel will not terminate a pregnancy if the fertilized egg has attached to the uterus.

What happens if I miss a dose?

Since this medicine is used as a single dose, it does not have a daily dosing schedule.

What happens if I overdose?

Because this medicine is supplied as a single tablet in an exact strength, an overdose is unlikely to occur when this medicine is used as directed. Do not take more than one tablet at the same time.

What to avoid

This medicine will not protect you from sexually transmitted diseases--including HIV and AIDS. Using a condom is the only way to protect yourself from these diseases. Avoid having unprotected sex.

Plan B One-Step side effects

Serious Plan B One-Step side effects:

Allergic reaction: Get emergency medical help if you have signs of an allergic reaction to this medicines. Symptoms may include hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Tubal (ectopic) pregnancy: Call your doctor or seek emergency medical help if you have severe pain in your lower stomach or side. This could be a sign of a tubal pregnancy (a pregnancy that implants in the fallopian tube instead of the uterus). A tubal pregnancy is a medical emergency that needs medical treatment immediately.

Common Plan B One-Step side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Plan B One-Step?

Certain other medications can make levonorgestrel less effective, which may result in pregnancy. Do not take this medicine without telling your doctor or pharmacist that you are using any of the following medications:

This list is not complete. Other drugs may interact with levonorgestrel, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide, to check for interactions with Plan B click on the link below.


Store tablet at room temperature 20–25°C (68–77°F)

What are the ingredients in Plan B One-Step?

Active ingredient: levonorgestrel 1.5 mg

Inactive ingredients: colloidal silicon dioxide, potato starch, magnesium stearate, talc, corn starch, lactose monohydrate


Teva Women’s Health, Inc.

Popular FAQ

Yes, Plan B (levonorgestrel) may lead to a delayed period or induce bleeding outside the typical menstrual cycle, as it contains a synthetic hormone. In order to prevent pregnancy, Plan B, similar to other contraceptive pills, needs to modify your hormonal levels, which can result in these menstrual alterations. It's worth noting that Plan B is linked to a higher likelihood of menstrual changes compared to regular birth control pills, due to its increased dosage. Continue reading

Yes. After taking the emergency contraceptive Plan B (levonorgestrel), it is considered safe to drink alcohol, and alcohol is not known to alter the efficacy of Plan B. While consuming alcohol after Plan B is not considered dangerous, some of the potential side effects of Plan B may be worsened by alcohol. Continue reading

Plan B (levonorgestrel) is estimated to be 60% to 94% effective at preventing pregnancy when taken within 3 days (72 hours) after unprotected sex. Somewhere between 0.6% to 2.6% of women who take Plan B within this time frame will still become pregnant. Continue reading

Despite what many people believe, there is no official weight limit for Plan B and there is no weight recommendation on the FDA label for Plan B. There is currently no reason or good evidence that women of a higher body weight or BMI cannot use Plan B or other forms of emergency contraception. Continue reading

You can take Plan B (levonorgestrel) as many times as needed for emergency contraception. There is no known limit on the number of times you can safely use Plan B. Plan B can even be taken more than once in the same menstrual cycle. Continue reading

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.