Plan B: What You Need to Know Before Taking the Morning-After Pill

By: Jay Dee, MPH

So You Need a Plan B!

Here are some things you need to know before you run to your local drugstore.

Plan B is a brand name for an emergency contraceptive pill containing levonorgestrel. It works primarily by stopping or delaying ovulation, which means it works best when taken before your ovary releases an egg.

Plan B should be taken as soon as possible after unprotected sex or birth control failure. The FDA recommends taking it within 72 hours (3 days), and the sooner you take it, the better your chances of preventing pregnancy.

But before we talk about Plan B, let's talk about ovulation.

What Happens During Ovulation?

Ovulation occurs when an ovary releases an egg into the fallopian tube. Once released, the egg can be fertilized for about 12–24 hours.

This is when pregnancy can occur if sperm is already present in the reproductive tract or reaches the egg during this window.

And here's something important: sperm can survive in the female reproductive tract for up to 5 days when cervical mucus is favorable.

Around ovulation, two important things are happening:

1. The uterine lining is prepared for a possible pregnancy. The lining has been building up throughout the menstrual cycle in preparation for a fertilized egg.

   
   

2. Cervical mucus changes. Around ovulation, cervical mucus becomes thinner, slippery, and stretchy. This makes it easier for sperm to travel through the cervix and reproductive tract.

   
   

Think of cervical mucus as a little highway for sperm.

After ovulation, if fertilization does not occur, the egg breaks down. Eventually, the uterine lining sheds during your period.

So, What Does Plan B Actually Do?

When someone takes emergency contraception like Plan B, the goal is to prevent or delay ovulation before it happens.

This is why timing matters so much.

If ovulation has already occurred, Plan B may not be effective because it does not stop an egg that has already been released. FDA information states that Plan B works before the release of an egg from the ovary.

And because you usually don't know the exact hour you're going to ovulate, you can't simply look at your calendar and know for sure whether you're ovulating.

Ovulation isn't like an appointment that happens every month at 1 p.m. on Tuesday.

Here Are Some Reasons Plan B May Not Work

1. Ovulation has already occurred

Plan B works primarily by stopping or delaying ovulation. If the egg has already been released, taking Plan B may be too late.

2. You waited too long

The clock matters!

Plan B should be taken as soon as possible and within 72 hours after unprotected sex or birth control failure. Waiting longer can reduce its effectiveness.

Remember: the clock is calculating hours, not just days!

3. Your body weight or BMI may affect how well it works

This is something many people don't know.

Research has raised concerns that levonorgestrel emergency contraception, including Plan B, may be less effective in people with higher body weight or BMI. However, there is not a simple 150-pound cutoff where Plan B suddenly stops working. It doesn't mean Plan B won't work—it means there may be a greater chance that it won't be as effective.

And this is important because Plan B is readily available at drugstores over the counter. No prescription is needed.

Next Option: Ella

If you're concerned about Plan B's effectiveness because of timing, body weight/BMI, or where you are in your cycle, another emergency contraceptive option is Ella (ulipristal acetate).

Ella is another emergency contraceptive pill that works by delaying ovulation. Unlike Plan B, Ella requires a prescription.

One of the benefits of Ella is that it can be taken up to 120 hours (5 days) after unprotected sex, although emergency contraception works best when taken as soon as possible.

The barrier? A prescription is needed.

And because we're talking about emergency contraception, having to get an appointment or prescription can create another delay.

Fun Fact:

Sometimes, if you haven't seen your healthcare provider within that year, they may require you to come into the office before prescribing medication—which can cause even more delay. But If you have, they are most likely to just send a prescription to your pharmacy of choice!

And when you're talking about emergency contraception, time matters!

Plan B vs. Ella: Which One Is Better?

The answer depends on when you had unprotected sex, whether ovulation may have already occurred, and your individual circumstances.

Plan B is convenient because you can walk into a drugstore and purchase it without a prescription. Ella requires a prescription but can be used later in the 5-day window.

The biggest takeaway?

Don't wait.

If you think you need emergency contraception, take action as soon as possible. The sooner you use emergency contraception, the better your chances of preventing pregnancy.

Hopefully, this gives you a better understanding of Plan B, emergency contraception, ovulation, and Ella so you can make a more informed decision when you need it.

Because when you're standing in the drugstore aisle Googling "Will Plan B work for me?" the last thing you need is confusing information.

Until Next Time,

The Vagina Liberator

FAQs: Plan B

Q. How long do I have to take Plan B?

A. Take Plan B as soon as possible, ideally within 72 hours (3 days) after unprotected sex.

Q. Does Plan B work if I’m already ovulating?

A. Plan B works by delaying ovulation, so it may not work if ovulation has already occurred.

Q. Does weight affect Plan B?

A. Plan B may be less effective at higher body weights or BMIs.

Q. What is Ella?

A. Ella is a prescription emergency contraceptive that can be taken up to 5 days after unprotected sex.

Q. Can Plan B cause an abortion?

A. No. Plan B prevents pregnancy primarily by delaying ovulation; it does not end an existing pregnancy.