When Do You Take Plan B? Plus, 7 More Plan B FAQs
Key takeaways:
Plan B One-Step (levonorgestrel) is an over-the-counter emergency contraceptive pill. It works by delaying ovulation (the release of an egg).
You should take Plan B as soon as possible. It’s most effective if you take it within 72 hours (3 days) after unprotected sex. But the sooner you take Plan B, the better it will work.
You can take Plan B if you’re already taking other forms of regular hormonal birth control, such as daily birth control pills. Plan B doesn’t interact with them and won’t impact their effectiveness.
Access savings on related medications
Table of contents
Emergency contraception is one of the many forms of birth control available. Plan B One-Step (levonorgestrel) — often called “the morning-after pill” — is one of the most well-known forms of emergency contraception. It’s also one of the most accessible. Plan B is available over the counter (OTC) and can be purchased by anyone of any age.
It’s common to have questions about Plan B, especially if you’ve never taken it before. Top of mind may be when to take Plan B or how it works to prevent pregnancy. Below, you’ll find answers to eight frequently asked questions, so you can make an informed decision regarding this emergency contraception pill.
1. When do you take the Plan B pill?
You should take Plan B as soon as possible. It’s still effective if you take it within 72 hours (3 days) of unprotected sex or birth control failure (such as a broken condom). But the sooner you take Plan B, the better it will work. For example, taking Plan B 12 hours after unprotected sex would be more effective than taking it 2 days after.
Can you take Plan B before sex?
No. You shouldn’t take Plan B before sex. This medication wasn’t studied for safety or effectiveness when taken this way. So experts can’t definitively say if Plan B would work to prevent pregnancy when taken ahead of time.
Other forms of regular birth control, such as daily birth control pills, are also more effective than Plan B is. So it’s recommended to consider other forms of contraception if you’re looking for something to take ahead of time.
Good to know: There are several OTC birth control options available. One of the most effective is Opill (norgestrel), an OTC birth control pill. This is a pill you’d take once daily to prevent pregnancy, just like prescription birth control pills. Consider Opill for daily contraception instead of taking Plan B before sex or multiple times per cycle.
Consider efficacy: Plan B can be up to 89% effective when taken as directed. Learn more about what can lower its efficacy.
OTC birth control pills: Plan B isn’t intended to replace daily contraception. Read about Opill, the first OTC birth control pill that’s meant for daily use.
Possible side effects: Learn about the most common Plan B side effects — from nausea to breakthrough bleeding — and how to manage them.
Lower costs: Generic versions of Plan B are just as effective as the brand name but have a lower cost. See how much generic and brand-name Plan B cost and how to save.
2. What is the active ingredient in Plan B?
Plan B and its generic versions contain 1.5 mg of the progestin levonorgestrel in each tablet. Progestins are a lab-made version of the natural sex hormone progesterone. When you take Plan B, it acts like progesterone in the body.
3. How does Plan B work?
Plan B works by delaying ovulation (the release of an egg). Without an egg present, sperm have nothing to fertilize. And a fertilized egg is necessary for a pregnancy to start.
Plan B is only effective if you take it before you ovulate during your menstrual cycle. Unlike many other contraceptives, Plan B doesn’t thicken cervical mucus to slow sperm’s movement towards an egg. It also doesn’t thin the lining of the uterus to prevent a fertilized egg from implanting. These additional actions allow other birth control methods to provide extra pregnancy prevention.
Because of this difference, Plan B isn’t effective once you ovulate. Ovulation typically happens in the middle of your menstrual cycle (around day 14 if you have a 28-day cycle). But most women don’t know exactly when they ovulate. And Plan B isn’t harmful if you take it during this part of your menstrual cycle. So it’s still recommended to take Plan B if needed after unprotected sex regardless of where in your cycle you are.
Good to know: Plan B isn’t an abortion pill. It works to prevent pregnancy. It won’t stop a pregnancy once it’s begun.
4. How many times can you take Plan B?
You can take Plan B as many times as you need to during one menstrual cycle. There’s no maximum monthly dosage. But you should only take one Plan B tablet at a time. And remember, it’s not intended for daily use in place of other birth control pills.
Taking more Plan B than recommended on the OTC label won’t make it more effective. And keep in mind that side effects are possible with every dose of Plan B you take.
5. Can you take Plan B while on birth control?
Yes. You can take Plan B even if you’re using other forms of birth control. Plan B doesn’t interact with hormonal contraceptives. If you’re going to be starting or restarting hormonal birth control after taking Plan B, you should use a barrier method of protection, such as condoms, for at least 7 days.
One notable exception to this is with ella (ulipristal), a prescription-only emergency contraceptive. Ella works differently from Plan B, and the two interact with each other. If you’ve taken ella in the past 5 days, you shouldn’t take Plan B.
6. Does Plan B cause weight gain or weight loss?
Plan B shouldn’t cause weight gain or weight loss. Body weight changes weren’t reported by people taking Plan B in its original clinical trials. In fact, most forms of birth control don’t cause weight gain.
It’s possible to experience bloating when taking progestin-based birth control. However, this is typically temporary and goes away with time. Keep in mind that this side effect is what’s known to happen with daily contraception. A one-time dose of Plan B is unlikely to cause noticeable bloating.
7. How long does Plan B stay in your system?
Plan B has a half-life of about 27 hours (a little more than 1 day). A half-life is the time it takes your body to clear about half of the medication from your system. In Plan B’s case, its half-life also represents when it has its greatest effects. But small amounts of the medication may be present in your body for about 5 and a half days.
8. Is Plan B safe to take?
For most people, Plan B is safe to take. It’s generally well tolerated, but side effects are possible. These include:
Your next period starting later
Heavier menstrual bleeding during your next period
Spotting or breakthrough bleeding
Nausea or vomiting
Lower abdominal (stomach) pain
Tiredness
Tender breasts
Most of these are mild in nature and resolve on their own within one menstrual cycle. If you throw up within 2 hours of taking Plan B, contact a healthcare professional. They may recommend you take another dose.
Plan B isn’t right for everyone, though. Ask a healthcare professional before taking Plan B if you:
Are allergic to levonorgestrel or other progestins
Are allergic to any of the inactive ingredients listed on Plan B’s label
Are pregnant
Take efavirenz (Sustiva)
Take rifampin (Rifadin)
Take seizure medications, such as carbamazepine (Tegretol, Equetro) or topiramate (Topamax)
Have not started menstruating yet
How to save on Plan B
Plan B is available OTC as a brand-name and generic medication. If a healthcare professional writes you a prescription for Plan B, GoodRx can help you save.
Save with GoodRx. GoodRx can help you save over 65% off the average retail price of the generic version of Plan B. Generic Plan B at certain pharmacies may cost as little as $12.27 with a free GoodRx discount.
Save with a coupon from the manufacturer. If you’re purchasing brand-name Plan B without a prescription, the manufacturer has a $10 coupon available to text or email to yourself or download and print from a computer. Just present it at the register during your purchase.
The bottom line
Plan B One-Step (levonorgestrel) is an over-the-counter emergency contraceptive pill. You should take Plan B as soon as you can after unprotected sex. While it’s still effective up to 72 hours (3 days) after sex, the sooner you take it, the better it works. You can take Plan B even if you take other forms of birth control, such as daily birth control pills. This emergency contraceptive pill doesn’t interact with other hormonal contraceptives.
Why trust our experts?
References
Centers for Disease Control and Prevention. (2023). Emergency contraception.
DailyMed. (2013). Label: Levonorgestrel tablet.
DailyMed. (2023). Label: Plan B One-Step - levonorgestrel tablet.
Haeger, K. O., et al. (2018). State of emergency contraception in the U.S., 2018. Contraception and Reproductive Medicine.
Society for Endocrinology. (2021). Progesterone.
The American College of Obstetricians and Gynecologists. (2021). Emergency contraception.
U.S. Food and Drug Administration. (2022). Decisional memorandum: New drug application 21998, supplement 5, levonorgestrel 1.5 mg tablet emergency contraceptive, labeling supplement for update to mechanism of action information.
