Yes, you can take Plan B during or right after your period, and nothing on the label says bleeding makes it work less well. Pregnancy from sex during a period is not very likely, but the NHS says it is possible, because sperm can survive for up to 7 days and some people ovulate early. If pregnancy would be a problem, the Plan B label says to take it as soon as possible within 72 hours (3 days) after unprotected sex, since the sooner you take it, the better it works.
Can you get pregnant from sex on your period?
It's possible, though not very likely. The NHS says sperm can survive in the fallopian tubes for up to 7 days after sex. In most women, ovulation happens around 10 to 16 days before the next period.
The NHS also says it's possible (although not very likely) to get pregnant soon after your period finishes if you ovulate early or have a short menstrual cycle. Sex late in your period, or just after it, can leave sperm still alive when an early egg is released.
No source we checked calls any part of the cycle safe for sex without contraception. That's why the useful question isn't "was I on my period?" It's "would a pregnancy be a problem right now?"
Does Plan B work if you take it during your period?
The label doesn't list being on your period as a reason not to take Plan B. The FDA says Plan B One-Step (levonorgestrel 1.5 mg) usually stops or delays the release of an egg from the ovary, so it works before ovulation. During or just after a period, ovulation usually hasn't happened yet, so there is still an egg release for it to delay.
The FDA says the most important factor in how well emergency contraception works is how quickly it is taken. The label's directions don't change based on where you are in your cycle.
- Take it as soon as possible within 72 hours (3 days) after unprotected sex. The label says the sooner you take it, the better it works.
- If you vomit within 2 hours of taking it, the label says to call a healthcare professional to find out if you should repeat the dose.
- Check your other medicines. The label says to ask a doctor or pharmacist first if you take efavirenz, rifampin, or seizure medicine, because these may make it less effective.
- It won't end a pregnancy. The FDA says it will not work if you are already pregnant and will not affect an existing pregnancy.
What if you're not sure the bleeding was a normal period?
If the bleeding came at an unexpected time, or was much lighter or shorter than usual, it may not have been a normal period. MedlinePlus lists abnormal vaginal bleeding and no periods as possible signs of an ectopic pregnancy, so unusual bleeding doesn't rule out a pregnancy that started earlier.
The FDA says Plan B will not work if you are already pregnant and will not affect an existing pregnancy. It can still help with the most recent sex. But if you also had unprotected sex earlier in the cycle and the bleeding seems off, ask a clinician or pharmacist whether you should take a pregnancy test too.
What happens to your bleeding after Plan B?
Plan B can change your bleeding for a cycle. The label lists menstrual changes as a possible side effect. MedlinePlus lists heavier or lighter than usual menstrual bleeding, and spotting or bleeding between periods.
MedlinePlus says your next period may come up to a week earlier or later than expected. The CDC says the cycle in which emergency pills are used might be shortened, prolonged, or involve irregular bleeding.
If you take it while you're already bleeding, the sources we checked don't say exactly how that period will be affected. Your next period is the one to watch. The Plan B leaflet says you will know it worked when your next period comes at the expected time or within a week of it.
When should you take a pregnancy test after Plan B?
Use your next expected period as the guide. The Plan B leaflet says that if your period is more than 1 week late, you may be pregnant, and you should get a pregnancy test and follow up with a healthcare professional.
The CDC gives clinicians a similar rule: advise a pregnancy test if there is no bleed within 3 weeks of taking emergency pills. If you're not sure when your period is due, the 3-week mark is a simple date to set a reminder for.
- Period comes on time or within a week: the leaflet says this is how you know Plan B worked.
- Period more than 1 week late: take a pregnancy test.
- No bleed 3 weeks after taking it: take a pregnancy test (CDC).
When should you get care?
In an emergency, call 911Get medical attention right away if you have severe belly pain after taking Plan B. The Plan B leaflet says severe abdominal pain may mean an ectopic pregnancy, and MedlinePlus says to call your doctor right away for severe lower belly pain 3 to 5 weeks after taking it.
Contact a clinician the same day if you have abnormal vaginal bleeding, lower belly or pelvic pain, or think you might be pregnant. MedlinePlus lists these as reasons to contact a provider about a possible ectopic pregnancy.
Call 911 if you have sudden, sharp, severe lower belly pain, feel faint or pass out, or have shoulder pain with belly pain. MedlinePlus lists these as possible signs of a ruptured ectopic pregnancy, which needs emergency help.
How our AI doctor decides when to send you to care ›What should you do for birth control after Plan B?
The label says Plan B is not for regular birth control, and it doesn't protect against HIV or other STDs.
The CDC says any regular birth control method can be started or restarted right after taking levonorgestrel emergency pills. The CDC also says to use condoms or not have sex for the next 7 days.
The CDC lists a copper IUD as another emergency option. It can be placed within 5 days of the first unprotected sex. Ask a clinician if you want to know more about it.
Common questions
Can I take Plan B on my period?
Yes. Nothing on the Plan B label says being on your period makes it work less well, and pregnancy from period sex is unlikely but possible. If pregnancy would be a problem, the label says to take it as soon as possible within 72 hours of unprotected sex.
Do I need Plan B if I had sex on the last day of my period?
It depends on whether a pregnancy would be a problem for you. The NHS says sperm can survive up to 7 days and you can get pregnant soon after a period if you ovulate early or have a short cycle. Late-period sex isn't risk-free.
Will Plan B make my period heavier or longer?
It can. MedlinePlus lists heavier or lighter bleeding and spotting between periods as side effects, and the CDC says the cycle can be shorter, longer, or irregular. Your next period may also come up to a week early or late.
If I get bleeding a few days after Plan B, does that mean it worked?
Not necessarily. Spotting between periods is a listed side effect. The Plan B leaflet says the sign that it worked is your next period arriving on time or within a week of when you expected it.
When should I take a pregnancy test after Plan B?
The Plan B leaflet says to test if your period is more than 1 week late. The CDC advises a test if you have no bleed within 3 weeks of taking it.
Can I start birth control right after taking Plan B?
Yes. The CDC says any regular birth control method can be started or restarted right away after levonorgestrel emergency pills. The CDC also says to use condoms or skip sex for the next 7 days.
Pymander is not a replacement for a physician and does not provide medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with questions about a medical condition. If you think you may have a medical emergency, call 911.