You know what the morning-after pill is, but do you know how it works and what it does to your body to prevent pregnancy before it happens?

Probably not, and that’s okay because you’re about to find out. Recently, I was featured in a Shape magazine article, “The Potential Side Effects of Plan B,” where I got to discuss exactly that and more, like how Plan B can affect you if you have uterine fibroids.

With access to such safety nets as emergency contraception, as well as a plethora of birth control options and barrier methods, the agency women have today over their own bodies is unlike any other time in our history.

To protect yourself and make the right choices, you need to know the facts: Plan B is a well-known emergency contraceptive you can rely on when you want to prevent unwanted pregnancies. But since it’s not designed to be used as a regular form of contraception, you shouldn’t take Plan B more than twice in a couple of months.
Ready to learn more? Here’s everything else you need to know and be aware of before you take Plan B.

Plan B: How It Works In Your Body

Commonly referred to as “the morning-after pill,” Plan B is emergency contraception that contains a concentrated dose of hormones called levonorgestrel, which is a type of progesterone, or sex hormone, that has long been used safely in many birth control pills.

Before you take Plan B, you should know that this hormone can affect your body in a multitude of ways.

Here’s how the pill generally works: Plan B interferes with the normal hormone patterns necessary for a pregnancy to occur. While you can take the pill within 72 hours after you’ve had unprotected sex, levonorgestrel is much more effective when taken within 12 to 24 hours.

If you’re wondering how Plan B is effective, these are the three steps:

  1. Plan B delays the release of an egg from the ovary
  2. It stops fertilization before it happens
  3. Then, it prevents a fertilized egg from attaching to the uterus

Remember that Plan B is back-up contraception and not your method of go-to birth control — it doesn’t disrupt pregnancy or cause an abortion, so you must take it before you’re pregnant.

Additionally, these pills are less effective than regular forms of birth control. If you need Plan B more than a couple of times per month, talk with your health provider about your many options for birth control that can be reliably used on a regular basis.

Many doctors agree that there are no clear dangers from taking Plan B more than once or twice, but it’s not recommended as a replacement for regular birth control.
Before you take Plan B, here’s something else to keep in mind: There’s been some concern over the effectiveness of it in women who weigh over 175 pounds.

In the Shape magazine article I was recently featured in, I shared how several years ago, two studies showed that after taking Plan B, women with a BMI over 30 had half the level of Plan B in their bloodstream compared to women with normal range BMI.

But after reviewing the data, the FDA realized there wasn’t enough evidence to force Plan B to change its safety or efficacy labeling.

How to Know When You Need to See a Doctor

Much like the tune of a prescription medication infomercial, Plan B pills do come with a laundry list of side effects, though you may not be impacted by them all. Plus, the side effects are typically temporary and harmless.

Here’s what you can expect to experience from the levonorgestrel hormone after taking Plan B:

  • Nausea
  • Abdominal pain
  • Fatigue
  • Diarrhea
  • Headache
  • Menstrual changes
  • Dizziness
  • Breast pain or tenderness
  • Vomiting

Though the effects can be harmless, do pay attention to how your body reacts. Remember you can always talk to your doctor when something feels off.

Some instances that require you to seek medical attention are:

  • Excessive bleeding
  • Abdominal pain
  • Excessive vomiting
  • Severe pelvic pain
  • If you vomit within two hours of taking Plan B
  • Signs of an allergic reaction (i.e., hives, difficulty breathing, or the swelling of your face, lips, tongue, or throat)

Finally, if you experience severe pain in your lower stomach or side, call your doctor. And if you don’t, your period within three weeks, consult a medical professional as soon as you can.

H2: Plan B and PCOS or Fibroids — Is It Risky?

If you have a condition like polycystic ovarian syndrome (PCOS) or uterine fibroids, good news! Taking Plan B is still considered generally safe and there is no added risk.

In fact, MedPage Today reported on two studies that found that ulipristal acetate, an emergency contraceptive, was also effective at controlling excessive bleeding associated with fibroids.

However, you should consult your doctor first, especially if you have a history of migraines, depression, pulmonary embolism, prior heart attack, stroke, or uncontrolled hypertension since these conditions have the potential for hormone complications.

How Plan B Interacts With Your Menstrual Cycle

Since Plan B works by stopping or delaying your ovulation, many women experience abnormalities with their periods after taking it.

The morning-after pill can cause your next period to be a few days to a week early or late, heavier or lighter than normal, longer than normal, and you might even experience more pain than you’re used to.
Because of the hormones in these pills, you might also notice spotting between periods, particularly right after taking an emergency contraceptive. But don’t fret if you encounter these symptoms — your period should return to normal by your next menstrual cycle.
If at least a week passes, however, and you still don’t get your period as expected, take a pregnancy test immediately.
It doesn’t matter where you are in your ovulation cycle when you take emergency contraception — just know it does matter that you take emergency contraception right after unprotected or under-protected sex in order for it to be most effective.

Meet Dr. Savita Ginde

Dr. Savita Ginde is an advocate and thought leader for reproductive health and served as Chief Medical Officer of Planned Parenthood of the Rocky Mountains for over 13 years. And, until very recently, she served as the Chief Healthcare Officer for STRIDE Community Health Center where she oversaw all of STRIDE’s healthcare services and led their COVID-19 vaccination efforts.