Table of ContentsView AllTable of ContentsHow Long Is Plan B Effective?ConsiderationsEffectivenessInteractionsSide EffectsWho Can Take itWhere to Get ItCost
Table of ContentsView All
View All
Table of Contents
How Long Is Plan B Effective?
Considerations
Effectiveness
Interactions
Side Effects
Who Can Take it
Where to Get It
Cost
Plan B One-Step (levonorgestrel)used foremergency contraceptionis most effective when taken as soon as possible after unprotected sex orbirth control failure. However, it can be effective for up to three days (72 hours) and sometimes up to five days.
Plan B decreases the chance of unintended pregnancy. It is available over-the-counter (OTC) at pharmacies, family planning clinics, or health department clinics. You do not need a prescription or identification to get Plan B One-Step, and people of any age or gender may buy it.
Plan B is not the same thing as theabortion pill,mifepristone(also known as RU-486), sold under the brand name Mifeprex.
This article will discuss when you should take Plan B to optimize its effectiveness, how it works to prevent pregnancy, the cost, and other important information.
Wladimir Bulgar / Getty Images.
Peak concentrations of levonorgestrel are reached in the blood within one to two hours of a dose.Thereafter, Plan B can continue to prevent LH surges forfour to five days.
This is the same timeframe during whichspermare still viable. Sperm can survive in thefemale reproductive tractand be capable of fertilizing an egg for four to five days. After six days, the ability of sperm to conceive pregnancy drops to less than 1%.
What Can Reduce How Long Plan B Works?
Plan B One-Step does not work if you have already ovulated.
Despite misconceptions that Plan B can prevent implantation of a fertilized egg, prevent sperm from entering the egg, or change cervical mucus to prevent sperm from reaching the egg, no such benefits have been found.
While Plan B One-Step may be able to prevent ovulation for up to five days, the level of protection decreases as the drug is gradually eliminated from the body.
Levonorgestrel has a relatively longhalf-life(meaning the time during which half of the drug is eliminated from the body), but it is more effective during the earlier part of treatment when drug concentrations are high than the tail end when drug concentrations are reduced.
At the same time, the half-life of levonorgestrel can vary, ranging from 20 hours to 60 hours. For people at a healthy weight, levonorgestrel has an average half-life of up to 46.4 hours, In contrast, levonorgestrel has a half-life of 26.4 hours in people withobesity.
This doesn’t mean that Plan B is less effective if you are overweight. It only highlights the need to take the drug as early as possible to improve your odds of protection.
How Effective Is Plan B?
Plan B One-Step is estimated to be 75% to 89% effective if taken within three days of unprotected sex. The sooner it is taken, the more effective it is.
It may also be effective—just not as effective—when taken four to five days after unprotected sex.
While Plan B One-Step is commonly called the “morning-after pill,” you do not have to wait until the next morning to take it.Experts recommend keeping a box on hand so that you can take it if a condom fails or is not used.
After taking emergency contraception, you should use barrier protection (such as acondom) and your regular birth control method for at least seven days if you have sexual intercourse.
Does Plan B Affect Future Pregnancies?Emergency contraception does not affect future fertility or any future chances of getting pregnant. This includes emergency contraceptive pills like Plan B as well as copper-containing intrauterine devices (IUDs) which can also be used for emergency contraception.
Does Plan B Affect Future Pregnancies?
Emergency contraception does not affect future fertility or any future chances of getting pregnant. This includes emergency contraceptive pills like Plan B as well as copper-containing intrauterine devices (IUDs) which can also be used for emergency contraception.
What Medications Interact With Plan B?
Certain drugs may interact can Plan B One-Step, making it less effective. These include:
If you take any of these drugs, ask your healthcare provider if it is reasonable to interrupt treatment for several days.Do not stopunless your provider gives you the OK. With some of these drugs, stopping can lead to withdrawal symptoms, drug resistance, or treatment failure.
You should also not take Plan B One-Step (or any levonorgestrel-based drug) if you have taken the emergency contraceptiveElla (ulipristal)in the past five days. Taking them this close together can counteract their effects and cause them to fail.
Can Plan B Cause Side Effects?
As with all drugs, Plan B One-Step can cause side effects. Some of the more common include:
If you vomit within two hours of a dose, contact your healthcare provider to see if you should repeat the dose.
Do not take more than one dose of Plan B. Taking more will not make the drug more effective and may only serve to increase the risk of side effects.
Do I Need a Pregnancy Test After Using Plan B?While it is common for your period to be temporarily lighter, heavier, or different after taking Plan B, it shouldn’t altogether cease. If you don’t get your period within three weeks of using Plan B,take a pregnancy testto see if you are, in fact, pregnant.
Do I Need a Pregnancy Test After Using Plan B?
While it is common for your period to be temporarily lighter, heavier, or different after taking Plan B, it shouldn’t altogether cease. If you don’t get your period within three weeks of using Plan B,take a pregnancy testto see if you are, in fact, pregnant.
Side Effects of Plan B One-Step
Who Can Take Plan B?
Plan B One-Step is indicated for any situation where you may be at risk of unintended pregnancy following sex, including:
Plan B One-Step is only used to prevent pregnancy after unprotected sex. it does not protect againstsexually transmitted infections (STIs)likeHIV.
In addition, Plan B One-Stepshould notbe usedif:
Where Can You Get Plan B?
Anyone of any age or gender can buy Plan B One-Step without a prescription. Identification is not required.
You can find Plan B One-Step (or generic versions of the drug) at:
How Much Does Plan B One-Step Cost?
You can purchase Plan B One-Step for about $40 to $50. There are generic versions that cost between $11 and $45, includingTake Action, My Way, Option 2, Preventeza, AfterPill, My Choice, Aftera, and EContra.
You can also check with your Planned Parenthood center, family planning clinic, or municipal health department to see if you can get Plan B at a lower cost or for free.
Summary
Plan B One-Step (levonorgestrel) is an emergency contraceptive used to prevent pregnancy following unprotected sex or birth control failure. It should be taken as soon as possible, ideally within three days (and possibly up to five days).
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Planned Parenthood.What’s the Plan B morning-after pill?Planned Parenthood.The difference between the morning-after pill and the abortion pill.DailyMed.Plan B One-Step - levonorgestrel tablet.International Federation of Gynecology and Obstetrics.Mechanism of action of emergency contraception.Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839U.S. Food and Drug Administration.Decisional memorandum: new drug application 21998, supplement 5 levonorgestrel 1.5 mg tablet emergency contraceptive labeling supplement for update to mechanism of action information. December 12, 2022.Kolles S.Sperm‐oviduct interactions: key factors for sperm survival and maintenance of sperm fertilizing capacity.Andrology.2022 Jul;10(5):837–843. doi: 0.1111/andr.13179American College of Obstetricians and Gynecologists.Emergency contraception.Natavio M, Stanczyk FZ, Molins EAG, et al.Pharmacokinetics of the 1.5 mg levonorgestrel emergency contraceptive in women with normal, obese and extremely obese body mass index.Contraception. 2019;99(5):306-311. doi:10.1016/j.contraception.2019.01.003New York State Department of Health.Emergency contraception for preventing pregnancy.Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Planned Parenthood.What’s the Plan B morning-after pill?Planned Parenthood.The difference between the morning-after pill and the abortion pill.DailyMed.Plan B One-Step - levonorgestrel tablet.International Federation of Gynecology and Obstetrics.Mechanism of action of emergency contraception.Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839U.S. Food and Drug Administration.Decisional memorandum: new drug application 21998, supplement 5 levonorgestrel 1.5 mg tablet emergency contraceptive labeling supplement for update to mechanism of action information. December 12, 2022.Kolles S.Sperm‐oviduct interactions: key factors for sperm survival and maintenance of sperm fertilizing capacity.Andrology.2022 Jul;10(5):837–843. doi: 0.1111/andr.13179American College of Obstetricians and Gynecologists.Emergency contraception.Natavio M, Stanczyk FZ, Molins EAG, et al.Pharmacokinetics of the 1.5 mg levonorgestrel emergency contraceptive in women with normal, obese and extremely obese body mass index.Contraception. 2019;99(5):306-311. doi:10.1016/j.contraception.2019.01.003New York State Department of Health.Emergency contraception for preventing pregnancy.Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Planned Parenthood.What’s the Plan B morning-after pill?Planned Parenthood.The difference between the morning-after pill and the abortion pill.DailyMed.Plan B One-Step - levonorgestrel tablet.International Federation of Gynecology and Obstetrics.Mechanism of action of emergency contraception.Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839U.S. Food and Drug Administration.Decisional memorandum: new drug application 21998, supplement 5 levonorgestrel 1.5 mg tablet emergency contraceptive labeling supplement for update to mechanism of action information. December 12, 2022.Kolles S.Sperm‐oviduct interactions: key factors for sperm survival and maintenance of sperm fertilizing capacity.Andrology.2022 Jul;10(5):837–843. doi: 0.1111/andr.13179American College of Obstetricians and Gynecologists.Emergency contraception.Natavio M, Stanczyk FZ, Molins EAG, et al.Pharmacokinetics of the 1.5 mg levonorgestrel emergency contraceptive in women with normal, obese and extremely obese body mass index.Contraception. 2019;99(5):306-311. doi:10.1016/j.contraception.2019.01.003New York State Department of Health.Emergency contraception for preventing pregnancy.Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.
Planned Parenthood.What’s the Plan B morning-after pill?
Planned Parenthood.The difference between the morning-after pill and the abortion pill.
DailyMed.Plan B One-Step - levonorgestrel tablet.
International Federation of Gynecology and Obstetrics.Mechanism of action of emergency contraception.
Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839
U.S. Food and Drug Administration.Decisional memorandum: new drug application 21998, supplement 5 levonorgestrel 1.5 mg tablet emergency contraceptive labeling supplement for update to mechanism of action information. December 12, 2022.
Kolles S.Sperm‐oviduct interactions: key factors for sperm survival and maintenance of sperm fertilizing capacity.Andrology.2022 Jul;10(5):837–843. doi: 0.1111/andr.13179
American College of Obstetricians and Gynecologists.Emergency contraception.
Natavio M, Stanczyk FZ, Molins EAG, et al.Pharmacokinetics of the 1.5 mg levonorgestrel emergency contraceptive in women with normal, obese and extremely obese body mass index.Contraception. 2019;99(5):306-311. doi:10.1016/j.contraception.2019.01.003
New York State Department of Health.Emergency contraception for preventing pregnancy.
Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.
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