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Plan B —also known as the “morning-after pill” —is a type of emergency contraception (EC).

It’s designed to be taken soon after unprotected penis-in-vagina sex to help prevent pregnancy.

Anyone who can become pregnant can take Plan B when needed —there isn’t an age restriction.

However, it isn’t regular contraception, so it should only be used in emergency situations.

For example:

  • if you had sex without a barrier
  • if the condom broke during sex
  • if you forgot to take your birth control pill the day before or after sex

If taken within 72 hours of unprotected sex, this form of EC can reduce the chance of pregnancy by 75 to 89 percent.

According to Plan B’s manufacturer, the sooner you take the pill, the more effective it is.

Certain medications can alter its effectiveness.

If you take any of the following, speak with a healthcare professional before buying Plan B:

Although the manufacturers advise taking Plan B within 3 days of unprotected sex, you can take it up to 5 days after penis-in-vagina sex.

Research has found that Plan B is “moderately effective” when taken between 72 and 120 hours after sex.

But remember that its effectiveness decreases the longer you wait.

There’s no official weight limit for Plan B.

But the pill may not be as effective for people who have a BMI of 30 or more or weigh 155 pounds or more.

After conflicting results, some researchers have recommended a greater level of counseling for people who fall into those two categories.

But they point out that there’s no reason to restrict Plan B.

More research is needed into whether a higher weight and BMI decreases the effictiveness of Plan B. For now, you’re free to take it, no matter how much you weigh.

However, other forms of EC (mentioned below) may be more effective.

Plan B only works to prevent a pregnancy — it can’t end one.

It helps prevent pregnancy by using a bigger dose of levonorgestrel, the synthetic hormone found in birth control pills.

This mimics the natural hormone, progesterone, delaying the release of an egg from the ovary, thereby preventing ovulation.

If no egg has been released, there’s nothing for sperm to meet, and therefore no fertilization. Plan B also prevents fertilization by making it more difficult for the sperm and egg to meet. Additionally, Plan B may prevent the fertilized egg from sticking to the uterus.

There’s been talk of Plan B also working to prevent a pregnancy after fertilization. But this is near impossible to prove, according to a 2019 review.

Plan B is considered safe. Although it contains a higher hormone dose than birth control pills, the hormone doesn’t remain in the body for a long time.

Of course, you may experience mild side effects, including:

  • headaches
  • abdominal pain or cramps
  • nausea or vomiting
  • dizziness
  • breast tenderness

Your menstrual cycle may also temporarily change.

This means your period could come earlier or later, and it could be heavier or lighter.

Some people even experience spotting in between periods, while some experience no change to their periods at all.

There isn’t much you can do to prevent these side effects.

But anti-nausea medicine and painkillers may help if you do experience any of the above.

If you vomit within 2 hours of taking this morning-after pill, speak with a healthcare professional to see if you need to take a second dose.

Remember that the biggest risk is that the morning-after pill fails. So, if your period is significantly late, take a pregnancy test.

It’s also wise to remember that you can become pregnant soon after taking Plan B, so ensure you use birth control before having penis-in-vagina sex again.

Expect to pay between $40 and $50 for Plan B.

As Plan B is a branded form of EC, it tends to be more expensive. Generic levonorgestrel pills cost less and work in the exact same way.

There are other ways to reduce the cost.

If you have insurance or Medicaid, for example, you may be covered for some form of EC.

No insurance? You may be able to get EC for free or at a much lower cost at a family planning clinic or local health department.

Plan B’s manufacturer also has a coupon and rebate scheme. Get $10 off by printing out this coupon and taking it to a store that stocks Plan B.

Alternatively, if you’ve already bought the morning-after pill, you can upload a picture of your receipt online or mail it in for a rebate.

Plan B is available over the counter at drugstores and pharmacies. So you don’t need a prescription or ID when buying it.

You may find it in the family planning aisle or need to ask the pharmacist to get it if it’s behind the counter.

Family planning clinics and local health departments, as well as Planned Parenthood centers, also offer the morning-after pill.

If you’d rather buy it online, you can buy directly from the manufacturer. Note that delivery takes around 4 to 6 days.

Stores like Walgreens and CVS also sell Plan B online.

Remember to always buy from a reputable retailer and try to buy in advance, as you can’t guarantee when it’ll be delivered.

Plan B can affect the timing of your next period.

But, if you haven’t had a period within 3 weeks of taking Plan B, it’s best to take a pregnancy test.

If you get a positive result, talk with a healthcare professional for advice on the options that are available to you.

Plan B isn’t the only form of EC out there. Here’s the lowdown on other EC options, how often you can use this form of contraception, and more.

Are there other EC pills you can take?


If you’re looking for an EC pill that’s more effective longer after unprotected sex, consider ella.

It’s known as an ulipristal acetate pill. It works by delaying or preventing ovulation.

Most importantly, it is said to remain consistently effective when taken up to 5 days after unprotected sex, reducing the risk of pregnancy by 85 percent.

It’s also more suitable for people with a higher BMI or weight. The only drawback is that you need a prescription to get hold of ella. Plus, it can be pricier than Plan B.

Copper IUD

There’s one other type of EC, but it doesn’t come in the form of a pill.

A copper intrauterine device (IUD) can be inserted into the uterus to prevent fertilization up to 5 days after unprotected sex.

It’s more than 99 percent effective if inserted within a 120-hour timeframe.

Of course, you’ll need to book an appointment with a healthcare professional to get an IUD.

But the best part is that you can use it as a regular form of birth control afterwards.

How often can you take EC?

You can take Plan B and other levonorgestrel pills as often as you need them.

There are no long-term side effects.

But ella does have a limitation: The label says you should only take it once during a single menstrual cycle.

It’s also advised not to take two different kinds of EC pills within 5 days of each other, as there’s a risk that they may not work.

Is there a way to stock up on EC?

It makes sense to buy EC pills in advance, so that you have it on hand if you ever need it.

Remember that the quicker you take some forms (like Plan B), the better they work.

You can stock up by purchasing in drugstores, pharmacies, or online — there are no restrictions.

Will EC affect your period?

EC is known to affect the timing of people’s periods.

Some experience an earlier period, while others find theirs comes later.

You may also notice changes in heaviness or light spotting in between taking the pill and your next period.

There’s also a link between regularly taking EC and irregular periods.

So it’s always better to use regular birth control instead of relying on Plan B, ella, and the like.

How long do I have to take Plan B for?

Plan B One-Step consists of one pill, which should be taken as soon as possible after having unprotected sex, missing a contraceptive pill, or contraception failure.

The pill can be taken with or without food, and should be swallowed whole, preferably with water. Plan B should be taken within 72 hours of unprotected sex, for a higher efficacy rate.

Is Plan B the same as the ‘abortion pill’?

Plan B isn’t an “abortion pill.”

Levonorgestrel works to halt pregnancy before it takes place. “Plan B prevents ovulation, so if you’re already pregnant, it won’t work,” says Dr. Amy Roskin, a practicing OB-GYN and the medical director of The Pill Club.

How will I know if Plan B worked?

Plan B is most effective if taken within 72 hours. However, if ovulation has already occurred, the medication might not be able to prevent pregnancy.

“If your period is more than a week late after taking Plan B, you may be pregnant. You should take a pregnancy test and follow up with a healthcare professional,” says Dr. Betsy Koickel of GoHealth Urgent Care.

There are lots of online resources packed with EC information and advice.

Take a look at the following:

Healthline has also published plenty about EC:

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.