This Is How Plan B ACTUALLY Works

We’re all so damn busy trying to drink enough water, remember other people’s birthdays, fall in love, moisturize, and find personal fulfillment, it’s only natural that on occasion, things don’t go according to plan. The same is true of our sex lives.

Fortunately, when sex is involved, the Plan B One-Step® moniker is as apt as they come. In the realm of contraception, if your standard plan fails you (or is forgotten), it’s a go-to backup option for pregnancy prevention. No, it’s not an all-the-time solution (it's emergency contraception, after all), and it won’t protect against STIs/STDs, but for the moments when you find yourself in need of a "plan B," it may just be your eminent saving grace.

That said, there are still plenty of misconceptions surrounding this particular emergency contraceptive. Thanks to the proverbial peanut gallery, plenty of us have been led to believe that it may become less effective with each use (it won't), that it’s the same as an abortion pill (it isn’t), or that it only works the morning after unprotected sex or a birth control failure (it actually works when taken within 72 hours of said unprotected sex).

So, in an effort to arm you with all of the real, bonafide facts you’ll need to make more confident, informed decisions about your sexual health, we partnered with Plan B One-Step to talk to two experts — Pari Ghodsi, MD, spokesperson for Power To Decide, and June Gupta, MSN, associate director of medical standards at Planned Parenthood — about what actually happens in your body when you use this emergency contraceptive.

On a micro level, each Plan B pill contains a hormone that’s similar to progesterone (your ovaries secrete progesterone each month to help the ovulation process along). If you read the box, you’ll see an ingredient listed as "levonorgestrel." This sounds like an obscure spell incantation, but it’s actually just the scientific name for a form of progesterone that was developed in a lab, rather than in your body. It's also the same hormone used in most popular birth control pills — just at a higher dose.

Once you ingest the pill, the hormone will release — and begin working to halt your ovulation process by preventing your ovaries from releasing any eggs.

Normally, as you begin ovulating, your body experiences a rise in a hormone called Luteinizing Hormone (LH for short). This lets your ovaries know that they should ramp up egg production because it’s baby-making time. In the midst of this process, however, Plan B works to prevent any of those eggs from being released into your fallopian tube for fertilization — which is why you should be taking the pill ASAP after unprotected sex. “It’s kind of like pulling the emergency brake on ovulation,” says Gupta.

“If you’re not ovulating, you can’t get pregnant,” Dr. Ghodsi adds. Unlike an abortion pill, Plan B prevents the pregnancy process before it can even begin. Without the union of sperm and egg, there can be no baby.

But before you go ahead and take the pill, there are some essential points to consider. For starters, we should address weight efficacy. You may have heard through the grapevine — or the internet — that Plan B won't work for women with a BMI over 25 kg/m2. The data is too limited to say for sure, but fortunately, the FDA confirms, "[We] continue to believe that all women, regardless of how much they weigh, can use this [emergency contraception] to prevent unintended pregnancy following unprotected sexual intercourse or contraceptive failure."

Next, you should know that it won't have any effect on an already existing pregnancy. It also can't be used as a regular form of birth control.

“It can’t be taken preemptively, and if you have unprotected sex a second time after [just having taken] the pill, it won’t continue to work,” says Dr. Ghodsi. “It’s your plan B because it can only be taken when plan A fails.Plan B should be taken within 72 hours of your unprotected sex or birth control failure, but Dr. Ghodsi advises that the sooner it's taken, the better it works.

“Until you’ve taken the emergency contraceptive, you still may be ovulating,” she explains. “In the time between the unprotected sex and your Plan B dosage, it is possible that your eggs can be released, and fertilized.” The good news: When Plan B is taken correctly, seven out of eight women who would have otherwise gotten pregnant will not.

“Pregnancy doesn't happen right after you have sex — that's why it's possible to prevent pregnancy a few days after you do it,” Gupta adds. “Sperm can live inside your body for up to seven days after sex, waiting for an egg to show up. So, if you ovulate during that time, the sperm can meet up with your egg and cause [fertilization].”

On the plus side, if you do take Plan B in time to halt your ovulation, the levonorgestrel from the pill will exit your body within days. There’s no lingering — which is one of the reasons why the hormone continues to be so well tolerated among women, with minimal, short-lived side effects.

“After you take [Plan B], it's totally normal for your next period to be different from what you’re used to,” says Gupta. “It may come earlier or later and be heavier, lighter, or more spotty. Or it may be the same as it normally is. You may get an upset stomach, feel lightheaded or dizzy, or have tender breasts for a short while. Everyone is different, and every body reacts differently.”

Listen: Plan A doesn't always pan out. We get it. But rest assured that you can be confident in your Plan B.