Plan B Side Effects: Here’s How Long They Last

Medically reviewed by Mary Choy, PharmD

Plan B One-Step (levonorgestrel)  is a form of emergency contraception that can prevent pregnancy after birth control failure or unprotected sex (also known as condomless sex). While it is generally considered safe and effective, people who take it may experience mild side effects that typically pass within 24 hours. If side effects persist for more than 48 hours or are severe, it is recommended to seek medical attention.

This article will discuss how long these side effects may last and what can be done to alleviate them.

What Is Plan B and How Does It Work?

Plan B is an emergency contraceptive available over-the-counter (OTC) without a prescription or ID. It can prevent pregnancy after unprotected sex or birth control failure. The medication comes in an aluminum foil blister package containing one 1.5 milligram (mg) tablet of levonorgestrel.

Birth control failure can happen in various ways, including forgetting to take the pill, a broken or expired condom, a diaphragm or cap that shifted during intercourse, or not using a condom.

Plan B works by delaying ovulation or altering egg release, thus inhibiting fertilization and thickening the endometrium to inhibit implantation. It can be used at any time during the menstrual cycle but won't protect against HIV/AIDS or other sexually transmitted infections (STIs). It will not work if you are already pregnant and will not affect an existing pregnancy.

Plan B, also known as the "morning-after pill," is most effective when taken within 72 hours after unprotected sex or contraceptive failure. It can reduce the risk of pregnancy by up to 89%.

Plan B One-Step is intended to be used as a backup or emergency contraception and not as a regular method of birth control. If you find yourself needing to use Plan B One-Step frequently, discuss alternative birth control and STI prevention methods with your healthcare provider.

Side Effects of Plan B

Common reactions associated with using Plan B include:

• Menstrual irregularities

• Nausea

• Lower abdominal pain

• Tiredness

• Headache

• Dizziness

• Breast tenderness

• Vomiting

• Diarrhea

Severe reactions to Plan B are rare and have not been reported in clinical studies.

How Long Do Plan B Side Effects Last?

Plan B One-Step is safe when used as directed. Although side effects may occur, they are typically mild and temporary, usually passing within 24 hours.

Based on its chemical properties, the medication should be eliminated from the body within a week after administering a single dose.

Here is what you can expect when using Plan B:

• Day 1 and 2: After taking the pill, you may experience nausea, vomiting, abdominal pain, tiredness, headache, dizziness, breast tenderness, diarrhea, and irregular menstrual bleeding. If you vomit within two hours of taking the pill, you should take another one to ensure its effectiveness.

• Day 3 and beyond: Most people will no longer experience the side effects of taking a Plan B pill after 24 hours. If these symptoms continue for more than 48 hours or are severe, you should see a healthcare provider.

• Days or weeks later: Menstrual changes such as spotting or bleeding before their next period are common experiences. Some changes may not appear until the next menstrual cycle, which may be days or weeks after taking the pill. If your period is over a week late, you should get a pregnancy test or see a healthcare provider. Seek medical attention if you experience severe lower abdominal pain three to five weeks after taking it. You may have a pregnancy outside the uterus, which is called an ectopic pregnancy.

How to Manage Plan B Side Effects

If you experience nausea after taking Plan B, consider taking an over-the-counter (OTC) anti-nausea medication an hour beforehand. If vomiting occurs within two hours, another dose may be necessary. OTC pain relievers can alleviate abdominal pain, headache, and breast tenderness. Consult your pharmacist for options to reduce nausea or relieve pain.

When to See a Healthcare Provider

Consult a healthcare provider if any side effects persist beyond 48 hours or are severe.

Seek medical attention immediately if experiencing severe lower abdominal pain three to five weeks after taking Plan B One-Step.

If your period is over a week late, consider the possibility of pregnancy and follow up with your healthcare provider.

Summary

Common side effects after taking Plan B include menstrual irregularities, nausea, lower abdominal pain, tiredness, headache, dizziness, breast tenderness, vomiting, and diarrhea. You may experience these side effects mildly, but they typically pass within 24 hours. OTC medication can help ease symptoms. See medical attention if symptoms persist for more than 48 hours or are severe.

Plan B is not intended for regular use. Consult with your healthcare provider about alternative birth control methods. Using an alternative method of birth control is important as Plan B will not offer lasting protection from pregnancy.

Frequently Asked Questions

Is cramping normal after taking Plan B?

Plan B One-Step may cause lower abdominal pain. However, seek medical attention if pain persists for three to five weeks after taking it. You may have an ectopic pregnancy, a pregnancy outside the uterus.

Can I take Plan B multiple times?

While Plan B is not intended for regular use, some people use it as their primary birth control method for occasional sex. Emergency contraceptives are less reliable than routine contraception since their failure rate, while low based on single-use, accumulates over time with repeated use.

If you have already used Plan B, it is safe to use it again for another instance of unprotected sex or birth control failure. However, emergency contraception does not provide long-term protection against future pregnancies—it only works to prevent pregnancy after one act of unprotected sex or birth control failure.

Can Plan B affect my menstrual cycle?

Plan B can cause menstrual irregularities due to its effect on delaying ovulation. Changes in period may occur, such as spotting, heavier or lighter flow, or early or late period. Most people will have their next period as expected, but if delayed beyond a week, get a pregnancy test and see a healthcare professional.

Read the original article on Verywell Health.