Sexual Health
plan b can remain in your system for a few days after you take it

Here’s How Long Plan B Stays In Your System After You Take It

And what to know about effectiveness and safety.

Originally Published: 
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Long before the Supreme Court overturned Roe v. Wade on June 24, stripping those who can get pregnant of their constitutional right to an abortion, reproductive health care and contraceptive options were already complex. Between IUDs that can be painful to insert, birth control pills that can have extreme side effects, and condoms that are only 98% effective when used correctly, preventing pregnancy is not always an easy task. That’s why, when all else fails, there’s an over-the-counter drugstore fave: Plan B One-Step. But even though Plan B is a popular tool for preventing pregnancy, questions still abound about what it really is and how it works — and how long Plan B stays in your system.

Plan B, also known as emergency contraception or the morning-after pill, isn’t intended to be anyone’s first choice of contraception — hence the name — but it works well in a pinch after unprotected sex or when other forms of birth control crap out on you. (That 10-year-old condom belongs in a museum, not on your partner’s genitals, mmmkay?)

Truth be told, Plan B isn’t 100% effective, either. But it’s most effective when taken within 24 hours of a sexual encounter, and anywhere between 75-89% effective when taken within 72 hours. And even though it’s called the morning-after pill, you don’t necessarily take it the next morning — the sooner you can take it after having sex, the more effective it’s going to be.

So maybe you had unprotected sex last night, and this morning you take emergency contraception as a precaution. Is that Plan B pill staying in your system for a while? And if so, what does that mean for your overall health? Elite Daily spoke with doctors to answer these questions and more about what’s really happening to your body when you take Plan B.

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What Is Plan B, And Why Would I Take It?

Plan B is a pill that you can buy over-the-counter at most major drugstores. It’s packed with a hormone called levonorgestrel, which is a progestin that can “prevent ovulation, block fertilization, or keep a fertilized egg from implanting in the uterus,” according to the Mayo Clinic.

Dr. Jenna McCarthy, M.D., advisor on the WINFertility Medical Board and a reproductive endocrinologist, tells Elite Daily that Plan B is used “when a person is sexually assaulted, has unprotected consensual sex, or experiences a contraceptive failure, like a condom breaking.” It’s there as a backup to help protect you from an unwanted pregnancy if you suspect that a pregnancy is possible.

One thing to note: Plan B is not an abortion pill, and is therefore not impacted by the recent Supreme Court ruling (though it may be in the future). Depending on where you live and your socioeconomic status, Plan B is either super accessible or may be harder to get your hands on. For starters, it’s not cheap — typically hovering around $50 a pack — and because of a “conscience clause” in some state legislatures, pharmacists and pharmacies in those states can refuse to provide contraceptive services on “religious” grounds.

How Long Does Plan B Stay In Your System?

Dr. Adeeti Gupta, founder and CEO of Walk In GYN Care, says Plan B can stay in your system for anywhere from 48 to 72 hrs. “Plan B is simply a longer-acting and higher dose of a specific type of progesterone pill that suppresses ovulation,” she says. Therefore, “it gets metabolized pretty fast.”

But just because it stays in your system for a few days doesn’t mean it’s protecting you from pregnancy all that time. If you have unprotected sex again the next day, yesterday’s Plan B is not going to cut it. You’ll have to take another dose (and cough up another $50) ASAP after each unprotected sexual incident if you’re trying to prevent pregnancy.

On the other hand, if Plan B doesn’t stay in your system long enough, it may not be effective. If you vomit shortly after taking Plan B, which can sometimes cause nausea, your body may not have had time for the pill to work — levonorgestrel takes about two hours to absorb into your system, so it’s possible you may need another dose.

Is Plan B Safe?

Dr. McCarthy says there are no serious health concerns with Plan B, but, as with most forms of contraception, there are a whole lot of potential side effects. Common side effects associated with Plan B include nausea, though taking it with food can help, and mild abdominal pain. If the pain becomes severe or persists for a few days, you should see your doctor.

“Additionally, since Plan B works by delaying ovulation, your next period may be delayed up to a week and may be heavier than usual,” Dr. McCarthy adds. “If your period is more than a week late, you should check a pregnancy test.”

Other potential side effects include hormonal acne flare-ups because of all the progestin.

Even though Plan B is relatively safe to use, Dr. Gupta says most doctors do not recommend using plan B regularly because it can “mess up your cycle and your hormone balance if taken frequently.”

That being said, she adds, “It is OK to use it as a once-in-a-while method.”

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Are There Alternatives To Plan B?

Aside from consistently implementing your regular birth control methods, Dr. Gupta says an alternative to taking the morning-after pill can actually be IUD insertion.

To prevent pregnancy, you can get a copper IUD inserted within five days of unprotected intercourse, she says. “It's a slightly painful and invasive procedure, so many women do not go for it, but it is highly effective.”

There are a handful of other emergency contraceptive brands to choose from, too, including Ella, Take Action, AfterPill, and My Choice, though none of them are effective in people who weigh more than 155 pounds (yikes). Plan B also has been proven less effective in people over 165 pounds. The Paragard copper IUD, however, is a suitable option for someone who exceeds the weight limit for pills.

All in all, your access to Plan B pills remains mostly intact, and it is still a good option for many people to prevent pregnancy when other options have failed. Whether you need Plan B now or just want to prepare for the future, it’s good to keep in mind the effectiveness of the pill at different stages as it makes your way through your system.

If you or someone you know has been sexually assaulted, you can call the National Sexual Assault Telephone Hotline at 1-800-656-HOPE (4673) or visit


Dr. Jenna McCarthy, M.D., advisor on the WINFertility Medical Board and a reproductive endocrinologist

Dr. Adeeti Gupta, founder and CEO of Walk In GYN Care

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