Everything You Should Know About Plan B

Morning-after pills like Plan B are emergency contraceptives. Here's how they work—and how they don't.
white pills
Photograph: Luca Giabardo/Getty Images

You’ve probably heard of Plan B One Step, commonly referred to as the morning-after pill. It’s an emergency contraceptive that prevents an egg from being fertilized. One common misconception is that it’s an abortion pill. It isn’t (we get into that more below). 

Plan B is actually a brand name, so while it is common to refer to the entire category as Plan B (like calling tissues Kleenex), other companies offer the same type of emergency contraceptive. Take Action, My Way, Option 2, Preventeza, AfterPill, My Choice, Aftera, and EContra are some of the brands you may see at your pharmacy.

There are many reasons someone may decide to not have a baby, none of which are anyone’s business but their own. The right to bodily autonomy should not be up for debate, but now that we’ve been made aware of the Supreme Court’s plan to overturn Roe v. Wade, it’s important for everyone to educate themselves on the methods available to prevent pregnancy.

What Does the Plan B Pill Do?

Plan B works by temporarily delaying ovulation. As OB/GYN Dr. Kerry-Anne Perkins explained via email, Plan B contains levonorgestrel, which is an ingredient you’ll find in many daily birth control pills (though it is in a higher dosage in Plan B). It temporarily stops the release of an egg from the ovary, and therefore stops that egg from being fertilized. “Essentially, Plan B is sort of in a race against your ovulation,” she says.

After unprotected sex—which could be the result of not using sufficient birth control, missed birth control pills, or a broken condom—sperm can live inside the body for around five days. If you ovulate any time within those five days, an egg is at risk of being fertilized. You should take Plan B within 72 hours of having sex, but the sooner the better. Despite Plan B’s reputation as the “morning after” pill, you don't have to, and shouldn't, wait to take it.

Is Plan B the Abortion Pill?

No. Plan B works by preventing pregnancy; it does not end an existing one. If you take Plan B after the egg has been fertilized, or even well into a confirmed pregnancy, it will not terminate it. That is why it’s vital that you take the pill as soon as possible after unprotected sex. If you are seeking an abortion, whether through the medication used to do so or an in-clinic procedure, you must see a doctor.

“Probably the most common [misconception] is that Plan B will cause an abortion,” Perkins, who is also on the medical review board of Women’s Health Interactive, says. “It won’t. Plan B simply delays ovulation—which occurs before fertilization does. If ovulation is stopped, fertilization won’t take place and pregnancy won’t occur. If you are already pregnant, Plan B will not abort the pregnancy.”

How Effective Is It in Preventing Pregnancy?

According to Planned Parenthood, Plan B and its ilk have a 75 to 89 percent chance of preventing a pregnancy. Perkins told me that about one out of eight people who take Plan B may still get pregnant.

How Do You Get Plan B?

Plan B is available without a prescription, and anyone of any age can purchase it. You can find it at CVS, Walgreens, Target, Rite Aid, and many other grocery stores and pharmacies, including online pharmacies like Wellspring Meds.

It typically costs around $50, but your local Planned Parenthood may also offer it for free or at a more manageable price. 

Does It Expire?

Plan B lasts about four years—though every box should have an expiration date you can check. After that date, it becomes less effective. 

It isn’t the worst idea to have one box around so you can take it immediately, but you don’t want to stockpile it. “After the recent abortion news, it may be tempting to hoard mass amounts of Plan B,” says Dr. Jessica Shepherd, chief medical officer of Verywell Health and an OB/GYN. “But because they expire, stockpiling isn’t worth it. This can also lead to a shortage for others that need it as well.”

Just as we saw people unable to find basics like toilet paper and cleaning supplies during the first few months of the Covid-19 pandemic, don’t leave others in your community without emergency contraceptives when they need them just so you can have them on hand for an unknown future date.

Are There Side Effects?

You might experience nausea and even vomiting—if you’ve ever had to take two or three birth control pills at once to make up for missed dosages, you’ll know that they can cause the same types of side effects. You may also have some abdominal pain and breast tenderness, as well as a delay in your next period.

Plan B is not a long-term method for preventing pregnancy, though it won’t cause fertility issues, no matter how often you’ve taken it. The doctors I spoke with confirmed that there are no studies to back up the myth that it causes infertility or birth defects.

Is There a Weight Limit?

Not technically, according to the doctors I spoke to, but those over 165 pounds may find it to be less effective. (FYI, that’s not heavy. According to Healthline, the average American woman 20 years old and up weighs 170.6 pounds.) “Limited research does suggest that emergency contraception pills may not work as well in people with over a certain body weight,” says Dr. Meera Shah, chief medical officer of Planned Parenthood Hudson Peconic, “165 pounds for levonorgestrel emergency contraceptives (e.g., Plan B) and 194 pounds for ulipristal acetate (ella).”

Ella is another type of emergency contraceptive that is better for those between 165 and 195 pounds. However, you must get a prescription for Ella.

The doctors I spoke with also recommended looking into IUDs (intrauterine devices) that can be placed up to five days after unprotected sex to be used as emergency (and long-term) contraception. This is more effective (99 percent) for someone who weighs more than 165 pounds, and IUDs last several years, but they must be inserted by a doctor, so those without insurance may not have access to that option. Insertion can also be uncomfortable.

Plan B and other emergency contraceptives are helpful for those of us with uteruses that we apparently have no right to control. But they’re not failure-proof, so it’s important to know all the facts.