How Long After Does Plan B Work

How Long After Does Plan B Work
This website stores data such as cookies to enable necessary site functionality, including analytics, targeting, and personalization. By remaining on this website you indicate your consent Cookie Policy x

Home Daily How long does plan b work after?

How long does it take to have caffeine withdrawal?

How long does Plan B work require not more than 72 hours after having unprotected sex. After having unprotected sex or without using contraception while sex, there is a chance to get the negative result of regular birth control. Plan B is not exactly for birth control, but it is excellent for emergency use.
How long should you wait before taking Plan B? Plan B One-Step should be taken within 72 hours of unprotected intercourse. When taken within 72 hours, it decreases the chance of getting pregnant by 89%. It’s even more effective when taken within 24 hours. Effectiveness decreases the longer a woman waits to take it.
How long does Plan B take to start working? If taken within 72 hours of unprotected sex, Plan B is 89 percent effective at preventing pregnancy, according to Planned Parenthood. The drug is less effective after three days, but can work up to five days after unprotected sex.
Is Plan B effective after 72 hours? Based on available data, Plan B is most effective if taken within the first 72 hours after unprotected sex but is still somewhat effective up to 5 days (120 hours) after unprotected sex. As mentioned, the sooner you take Plan B, the better.
How long does nausea last after taking Plan B? Nausea and Vomiting. The most common side effect associated with Plan B is nausea, which usually goes away within 24 hours . According to the American College of Obstetricians and Gynecologists, or ACOG, Plan B causes nausea in approximately 18 percent of women with only 4 percent experiencing vomiting.
How long should you wait before taking Plan B? Plan B One-Step should be taken within 72 hours of unprotected intercourse. When taken within 72 hours, it decreases the chance of getting pregnant by 89%. It’s even more effective when taken within 24 hours. Effectiveness decreases the longer a woman waits to take it.
What happens if you take Plan B too late? What are the risks of Plan B. Plan B uses a synthetic hormone traditionally used in birth control pills. The dosage is high, but serious side effects are uncommon. Typical and expected side effects include vomiting, nausea, fatigue, diarrhea and menstrual irregularities . If your period is more than seven days late,…
How long does Plan B last after you take it? “plan b” can stay in your system for up to five days , though it is not effective after three days max. If you have taken it, anticipate an irregular period afterwards. This is typical.
Should I get my period soon after taking Plan B? Women who took Plan B within 1-2 days before or after ovulation started their periods when they expected them. Women who took an emergency contraceptive more than two days before ovulation got their period at least one day earlier than usual.
Copyright © 2022 All Rights Reserved.

How Plan B Works Before and After Ovulation

Verywell Health's content is for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

Ⓒ 2022 Dotdash Media, Inc. — All rights reserved

Dawn Stacey, PhD, LMHC, is a published author, college professor, and mental health consultant with over 15 years of counseling experience.

Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more .

Medically reviewed by
Monique Rainford, MD

Learn about our
Medical Expert Board

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Emergency Contraception vs. Abortion Pills: What to Know Right Now

My Way Morning-After Pill for Emergency Contraception

Ella (Ulipristal) Oral: Uses, Side Effects, Dosages

Infertility: Symptoms, Causes, Treatment

How Is the Morning-After Pill Different From the Abortion Pill?

What You Should Know About Stockpiling Plan B

The Great Emergency Contraception Debate

How Hormonal Birth Control Prevents Pregnancy by Stopping Ovulation

What You Need to Know About Using the Morning-After Pill

Is Plan B Really Less Effective for People Above a Certain Weight?

Can Taking the Birth Control Pill While Pregnant Hurt My Baby?

What Is Plan B One-Step for Emergency Contraception?

You Can Prevent Pregnancies With More Than Just the Pill

Progestin for Emergency Contraception and Birth Control

Verywell Health's content is for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

Ⓒ 2022 Dotdash Media, Inc. — All rights reserved

Verywell Health is part of the Dotdash Meredith publishing family.

Monique Rainford, MD, is board-certified in obstetrics-gynecology, and currently serves as an Assistant Clinical Professor at Yale Medicine. She is the former chief of obstetrics-gynecology at Yale Health.

Plan B One-Step is an emergency contraceptive. Emergency contraceptives are used to prevent pregnancy after birth control failure or unprotected sex. Generic forms of Plan B include My Way , Take Action , and Next Choice One Dose .

Emergency contraception is safe and effective. Still, Plan B is controversial . Much of the debate is based on a misunderstanding about how Plan B works.

Some people believe Plan B prevents a fertilized egg from implanting in the lining of the uterus. This belief is based on the product's FDA labeling. Research, however, has not confirmed the information on the FDA label.

This article will discuss the controversy around the FDA labeling for Plan B. It will also look at what research says about how Plan B actually works.

According to the product label, Plan B prevents or delays ovulation, or the release of an egg. It may also prevent fertilization, when an egg and sperm combine.

The debate is based on another statement made on the label. Under "How does Plan B One-Step work?" the label says: “It is possible that Plan B One-Step may also work... by preventing attachment (implantation) to the uterus (womb).”

The medical community does not agree on the definition of pregnancy. 1 The legal definition of pregnancy "encompasses the period of time from implantation until delivery." 2

Some people, though, believe pregnancy begins when an egg is fertilized. People who hold this belief see Plan B as a form of abortion . This is because it is said to prevent implantation of a fertilized egg.

Research does not support this theory about how Plan B works, though. 3 In fact, studies have shown that Plan B does not decrease the rate of pregnancy when taken after ovulation. 4 This suggests it may not interfere with fertilization or implantation, just ovulation.

Most research suggests that Plan B does not cause changes in the endometrium , or lining of the uterus. 3 Because of this, researchers have concluded it cannot prevent implantation of a fertilized egg.

Plan B is not 100% effective at preventing an unintended pregnancy. It is also less effective the longer you wait to use it. Many researchers think this is because it does not prevent implantation.

Research shows Plan B does not cause any changes in the lining of the uterus. Therefore, it would not prevent implantation of a fertilized egg.

During Plan B's approval process, its manufacturer asked the FDA to remove the implantation piece from its label. It is not completely clear why the FDA chose to keep it there.

Most of the research done during the approval process focused on Plan B's active ingredient, the progestin hormone levonorgestrel . The research looked at the hormone's safety and its effectiveness at preventing pregnancy. These studies did not explore how Plan B works.

The FDA may have decided to include implantation on Plan B’s label because this is one of the ways birth control pills work . Birth control pills containing levonorgestrel or a different progestin change the lining of the uterus. The FDA may have decided that because the pill may do this, Plan B might, too.

But there are two things to keep in mind:

According to those involved in the Plan B approval process, the FDA thought it was important to include on the label the possibility that Plan B works "theoretically ... by interfering with a number of physiological processes." 6 This is why it included a list of all the possible ways that Plan B works.

Even though there was no scientific proof that Plan B works by preventing eggs from implanting, this claim was still included by the FDA on the drug’s label.

The FDA is has no plans to change the label. 7 But Erica Jefferson, an FDA spokesperson, did tell the New York Times that "the emerging data on Plan B suggest that it does not inhibit implantation." Research is clear that Plan B does not interfere with implantation. It works primarily by preventing ovulation. 8

Because of this, the research community and many in the medical field feel the language about implantation should be removed from Plan B labeling. 7

The FDA labeling for the Plan B emergency contraceptive says Plan B may work by preventing implantation of the fertilized egg. This has created controversy over its use. Research, however, shows that Plan B does not work this way. Instead, it works by preventing ovulation and fertilization of the egg.

Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life.
There was an error. Please try again.
Chung GS, Lawrence RE, Rasinski KA, Yoon JD, Curlin FA. Obstetrician-gynecologists' beliefs about when pregnancy begins . Am J Obstet Gynecol. 2012;206(2):132.e1-7. doi:10.1016/j.ajog.2011.10.877
Gemzell-Danielsson K, Berger C, Lalitkumar PGL. Emergency contraception — mechanisms of action . Contraception . 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021
Novikovaa N, Weisberg E, Stanczyk FZ, Croxattod HB, Fraser IS. Effectiveness of levonorgestrel emergency contraception given before or after ovulation — a pilot study . Contraception . 2007;75:112-118. doi:10.1016/j.contraception.2006.08.015
Gemzell-Danielsson K, Berger C, Lalitkumar PGL. Emergency contraception — mechanisms of action . Contraception . 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021
There was an error. Please try again.

All

Select the section you want to search in

All
Consumer
Professional
Pill ID
Interactions
News
FDA Alerts
Approvals
Pipeline
Clinical Trials
Care Notes
Natural Products

Browse all medications:

a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
0-9

Advanced Search

Medical Answers
How effective is Plan B and how late can you take it?

I accept the Terms and Privacy Policy

Select one or more newsletters to continue.

Ad Choices

We comply with the HONcode standard for trustworthy health information.

Copyright © 2000-2022 Drugs.com. All rights reserved.

Medically reviewed by Sally Chao, MD . Last updated on July 30, 2021.
Plan B ( levonorgestrel ) is estimated to be 60% to 94% effective at preventing pregnancy when taken within 3 days (72 hours) after unprotected sex. Somewhere between 0.6% to 2.6% of women who take Plan B within this time frame will still become pregnant.
While Plan B can be taken up to 72 hours after unprotected sex, its efficacy decreases with time, and it is best to take it as soon as possible. For example, the chances of pregnancy are higher if Plan B is taken 4 days after unprotected sex, but are subsequently lowered if taken 3 days, 2 days, 1 day or within 24 hours after unprotected sex. However, the American College of Obstetricians and Gynecologists notes that some studies suggest that it can be moderately effective at preventing pregnancy up to 5 days after unprotected sex. Five days after unprotected sex is the latest time with which Plan B has been shown to lower your chances of pregnancy.
The efficacy of Plan B is also affected by the time at which it is taken within your menstrual or reproductive cycle. Plan B works best when taken before ovulation, or when an ovary releases an egg. Once there is a surge in the hormone that initiates ovulation and ovulation begins, Plan B cannot prevent pregnancy. Its primary mechanism of action is to change hormone levels such that ovulation is delayed. This is why it is important to take Plan B as soon as possible after unprotected sex. As treatment is delayed, ovulation becomes more imminent (if it has not yet occurred).
A review of studies in Clinical Obstetrics and Gynecology showed that among 492 women who took Plan B after unprotected sex, those who took it on or after the day of ovulation had the same pregnancy rate as would be expected among women who used no contraception at all. By comparison, none of the women who took Plan B before ovulation became pregnant.
In the event of another unprotected sexual encounter after Plan B is taken, Plan B will not protect against pregnancy—you will need to take Plan B again after another unprotected sexual encounter.
Plan B may also be less effective at preventing pregnancy in women who are overweight or obese. Studies reviewed by Cochrane suggest that the dose of levonorgestrel in Plan B has a lowered potency when taken by women who have a higher body mass index.
The easiest way to lookup drug information, identify pills, check interactions and set up your own personal medication records. Available for Android and iOS devices.
Subscribe to Drugs.com newsletters for the latest medication news, new drug approvals, alerts and updates.
Drugs.com provides accurate and independent information on more than 24,000 prescription drugs, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. Data sources include IBM Watson Micromedex (updated 5 July 2022), Cerner Multum™ (updated 27 June 2022), ASHP (updated 16 May 2022) and others.
Help support Drugs.com by allowing ads...

Find out more in our Cookie Policy . You can disable cookies anytime in your browser settings.
Does Plan B Always Work? Morning-After Pill Q&A with Experts

Health

Sex

Lifestyle

Menopause

Puberty

Diseases

Symptoms

Lifestyle

Beauty

Mental health

Planning for pregnancy

Trying to conceive

Trouble conceiving

He Licked My Clit
Pussy Is Too Small
Wife Forced Sex Story

How Long After Does Plan B Work

Report Page