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Emergency contraception (EC) can affect the length of your menstrual cycle, meaning that your next period may come later or earlier than expected.

Getting your period after taking EC, like Plan B, signifies you’re not pregnant. So it’s understandable that you’ll want to know exactly when to expect your period.

But everyone is different, and you may find that your period arrives around a week earlier or later than typical.

The hormones found within Plan B can alter your next period in several ways. While some people may notice no change, others have reported everything from different durations to heavier bleeding.

Here’s what to expect.


It’s hard to predict exactly when your first period after taking Plan B will arrive. Some people have their period at the usual time, while others experience it a few days earlier or later than expected.

Some research suggests that the earlier in your menstrual cycle you take Plan B, the earlier your next period will be.

However, this hasn’t been conclusively demonstrated.


Just as with timing, the duration of your period may change too. However, there’s a chance it may last for the same amount of time as usual.

Research has found that taking EC both before ovulation and later in the menstrual cycle can make a period last longer than normal.

Overall characteristics

You may notice lighter or heavier bleeding than usual after taking Plan B.

Changes to bleeding intensity may be more likely if you’ve used Plan B more than once in a month or more than once in a single menstrual cycle.

Other symptoms

Although Plan B can cause side effects ranging from nausea to headaches, these symptoms usually disappear after 24 hours.

So by the time your period arrives, you may not feel anything different other than the usual cramps and tenderness.

However, if your period is heavier than normal, you may feel tired and notice a lack of energy.

Menstrual products to use

You can use your usual menstrual products during your first period after taking Plan B.

But particularly heavy periods may warrant a double layer of protection, such as a tampon and a pad.

It’s normal to experience light bleeding, or spotting, after taking Plan B. It’s usually nothing to worry about if it happens to you.

Spotting is a side effect of the extra hormones that the EC pill releases inside your body. But it can also be a sign of early pregnancy, so try to keep track of your menstrual cycle and take a pregnancy test if you feel unsure.


Bleeding tends to occur a few days after taking Plan B. But some people may never experience spotting.


It can last a day or two but may stick around for longer. As with everything, the answer depends on the unique way Plan B’s hormones affect your body and cycle.

Overall characteristics

Spotting won’t look like an actual period. Instead, it’s much lighter, often appearing as a few spots of blood on toilet paper or your underwear. The color can be anything from pink and red to brown.

Other symptoms

As Plan B-related bleeding is different from your usual period, it’s unlikely you’ll experience typical menstrual symptoms like severe cramps.

However, it may come with one or more Plan B side effects such as:

  • nausea
  • stomach pain
  • fatigue
  • headache
  • dizziness
  • breast tenderness
  • vomiting
  • diarrhea

These shouldn’t last longer than a couple of days.

Menstrual products to use

The bleeding that can occur after taking Plan B is usually very light, so you won’t need heavy forms of menstrual protection.

But if you’re concerned that it may soak through your underwear, consider wearing a panty liner.

There’s no way to know if Plan B worked other than to wait for your period.

Remember that spotting or light bleeding isn’t the same as a period, so you may have to wait a few weeks before knowing either way.

Plan B uses a synthetic hormone called levonorgestrel to prevent pregnancy by stopping an egg from being released.

Levonorgestrel is found in birth control pills, but Plan B contains a higher dose that can alter your body’s natural hormone levels.

The extra hormones can, in turn, affect the menstrual cycle, leading to an earlier or delayed period as well as heavier or lighter bleeding.

It’s normal for Plan B to affect the timing of your period. But if it’s a week later than usual or still hasn’t arrived within 3 weeks of taking Plan B, there’s a possibility that you’re pregnant.

EC pills containing levonorgestrel can reduce the chance of pregnancy by 95 percent if taken within 24 hours of sex. This lowers to 88 percent if the pill is taken between 24 and 72 hours after sex.

If you’re unsure whether Plan B has worked, take a pregnancy test.

Take one straight away if you keep track of your cycle and know that your period is at least a week late.

But if you’re not sure where you are in your menstrual cycle, wait 3 weeks after taking Plan B before using a pregnancy test.

Pregnancy tests detect a specific type of hormone, human chorionic gonadotropin (hCG), which is only produced a few days after conception. So taking one too early can produce a false result.

If your test comes back negative, wait a couple more weeks to see if your period arrives.

If it doesn’t, take another pregnancy test and visit a doctor for advice on delayed periods if the result comes back negative once again.

If the result is positive, book a doctor’s appointment. They’ll be able to confirm your pregnancy and talk you through all the available options, including both medical and surgical abortions.

Plan B affects people in different ways, so it’s impossible to predict whether your menstrual cycle will change.

But having your first post-Plan B period a week earlier or later than normal is nothing to worry about. And remember that these changes are only temporary, as your cycle should right itself the next time round.

If you’re still experiencing early or late periods or abnormal bleeding levels, talk with a doctor or other healthcare provider.

Lauren Sharkey is a U.K.-based journalist and author specializing in women’s issues. When she isn’t trying to discover a way to banish migraines, she can be found uncovering the answers to your lurking health questions. She has also written a book profiling young female activists across the globe and is currently building a community of such resisters. Catch her on Twitter.