Plan B (the “morning‑after pill” with levonorgestrel) can cause short‑term, usually mild side effects, mostly around your next period and your stomach.

Quick Scoop

  • Most people feel okay after Plan B and do not have serious problems.
  • Common side effects show up within hours to a few days and usually go away on their own within a few days to a week.
  • It can temporarily change your next period (timing and flow), but it is not known to cause long‑term fertility problems.
  • Get urgent medical help if you have severe belly pain, very heavy bleeding, or think you might already be pregnant (ectopic pregnancy risk).

What Plan B Is

Plan B One‑Step is a single‑dose emergency contraception pill containing levonorgestrel, a hormone also used in many regular birth control pills.

It works mainly by delaying ovulation so that sperm and egg do not meet; it does not end an existing pregnancy and is not the same as the abortion pill.

Common Short‑Term Side Effects

These are the things people most often notice after taking Plan B. They usually start within hours to a couple of days.

  • Changes in your next period:
    • Heavier, lighter, earlier, or later than usual.
* Spotting or breakthrough bleeding before your next full period.
  • Stomach and pelvic symptoms:
    • Lower abdominal or pelvic cramps, similar to period cramps.
* Nausea; some people vomit.

* Occasionally other GI issues like bloating, constipation, or diarrhea.
  • General symptoms:
    • Fatigue/tiredness.
* Headache.

* Dizziness or lightheadedness.

* Breast tenderness/soreness.

Most of these effects are described as mild and short‑lived; many people have some symptoms for a day or two, and most are gone within a few days.

How Long Side Effects Last

  • Period changes:
    • Heavier or lighter flow and spotting usually affect only the next cycle; most people return to their usual pattern afterward.
  • Nausea, cramps, headache, fatigue, breast soreness:
    • Often start within a few hours and tend to improve within 24–72 hours.

Plan B is not known to have lasting or permanent side effects in otherwise healthy users.

Serious or Less Common Risks

Serious problems are rare, but it’s important to know the red flags.

  • Possible ectopic pregnancy (pregnancy outside the uterus, often in a tube):
    • Warning signs: severe lower abdominal pain that doesn’t improve, pain on one side, shoulder pain, dizziness/fainting, or very heavy bleeding.
* This needs emergency care because it can be life‑threatening.
  • Very heavy bleeding:
    • Soaking a pad or tampon every hour for several hours, or passing large clots.
* This should be checked urgently by a clinician.

If you vomit within about 2 hours of taking Plan B, you may need another dose—call a pharmacist, clinic, or doctor.

Does Plan B Affect Fertility or Future Health?

  • Current evidence and major health organizations say Plan B does not cause infertility and does not harm future ability to get pregnant.
  • It is meant for occasional emergency use, not as your main birth control, but taking it more than once is medically allowed if needed (you may see more cycle irregularity).

Simple Things That Might Help You Feel Better

These comfort tips are general and not a substitute for professional medical advice:

  1. For cramps or headache:
    • Non‑prescription pain relievers like ibuprofen or acetaminophen are commonly used and are not known to interfere with Plan B’s effect.
  1. For nausea:
    • Taking the pill with food, sipping ginger or peppermint tea, and staying hydrated may ease queasiness.
  1. For breast tenderness:
    • Supportive bra, warm compresses, and gentle over‑the‑counter pain relief if needed.

Always check with a clinician or pharmacist if you have other medications or conditions before adding medicines.

When To Take a Pregnancy Test or Call a Doctor

Consider a pregnancy test and/or medical advice if:

  • Your period is more than about one week late after taking Plan B.
  • You have ongoing or worsening pain, nausea, or bleeding lasting more than a few days.
  • You suspect you were already pregnant when you took Plan B or you have ectopic pregnancy warning signs.

Mini “Forum-Style” View: What People Often Ask

“My period is late and I took Plan B. Is that normal?”
A slightly late (or early) period is very common after Plan B, but if it’s more than a week late, take a pregnancy test and talk with a provider.

“I felt really sick and crampy for a couple of days—did Plan B mess up my body?”
Short‑term nausea, cramps, and fatigue are expected for some people and usually resolve quickly; there is no strong evidence that a single dose causes long‑term harm.

“Can I keep using Plan B instead of regular birth control?”
It’s safe as emergency backup but less effective and more cycle‑disruptive than ongoing birth control, so clinicians recommend a regular method if you’re having sex that could lead to pregnancy.

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Information gathered from public forums or data available on the internet and portrayed here.