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How Long Does Plan B Stay in Your System?

cartoon of plan b pills

Birth control pills are a popular method of preventing pregnancy, but they are not 100% effective. Similarly, condoms prevent pregnancies but can occasionally leak, tear, or slip off. Emergency contraceptive pills or morning-after pills like Plan B One-Step are an option to prevent pregnancy after unprotected sex, for example, if you forget to take your regular birth control or if the condom breaks during sex. 

Please continue reading to learn more about Plan B emergency contraception, including how it works, when you should take it, and how long it stays in your body.

What is Plan B emergency contraception? 

Plan B One-Step is a progestin-only morning-after pill that contains levonorgestrel. It is used for emergency contraception to prevent an unwanted pregnancy after unprotected intercourse or contraception failure. 

Another brand of emergency contraception is called the Ella morning after pill. This pill is a prescription medication containing ulipristal acetate. 

A morning-after pill like Plan B is solely intended as backup contraception. It should not be used as a primary method of contraception or a replacement for a regular birth control pill. 

How does it work?

Plan B contains levonorgestrel, which is a synthetic form of the hormone progesterone. Levonorgestrel is absorbed into the bloodstream within a couple of hours, then assert its effects on the ovaries and uterine lining. It prevents pregnancy in various ways. The exact mechanism of action depends on the phase of the menstrual cycle. Meaning, Plan B can stop the ovary from releasing an egg; however, if the egg is already released and fertilized, Plan B can prevent it from attaching to the uterine wall.

Is Plan B available over the counter?

Plan B One-Step is available over the counter without a prescription at pharmacies. There is no age or gender restrictions for buying emergency contraceptive; meaning, anyone of any age and any gender can buy this medication. 

Who can take Plan B morning-after pill?

Any sexually active woman can take Plan B One-Step for the prevention of pregnancy after unprotected sexual intercourse or potential contraceptive failure. You should not use emergency contraception if you are pregnant or suspecting a chance of pregnancy. Similar to other medications, the morning-after pill carry risks, therefore, it isn’t appropriate for everyone. For instance, this type of medication is not intended to be used by postmenopausal women and younger gilrs who haven’t had their menstrual cycle. In addition to that, certain medications and dietary supplements can interact with the active ingredient of the morning-after pill. If you have questions, don’t hesiate to talk to your doctor or local pharmacist to make sure this type of emergency contraception is safe and effective for you.  

When should you take the morning after pill?

Plan B works best if the pill is taken within 72 hours of unprotected sex or contraception failure. So, you have a 3-day window to take Plan B; however, it is important to know that the earlier you take it, the more effective it is.

You can take Plan B at any time during your menstrual cycle. However, keep in mind that it is only meant to be used as an emergency contraceptive pill. If you have a positive pregnancy test, Plan B will not work as an abortion pill.

How long does Plan B stay in the body?

As mentioned, Plan B works best within the first 3 days after unprotected intercourseor failure of regular birth control. You should take the pill as soon as possible, ideally within 24 hours. 

Once you take Plan B, it’s only effective for about 5 days. After this time, the plasma concentrations of the synthetic hormone produced by this medication fall to negligible levels. Five days is also amount of time that sperm can survive in the female reproductive tract.  

How often can you take Plan B for birth control?

There is no limit on how often you can use Plan B as emergency contraception to prevent an unwanted pregnancy. Emergency contraception pills like Plan B are generally safe for most people and do not pose any significant health risks.Taking Plan B multiple times does not make it less effective or cause any long-term side effects. Be mindful that multiple use of Plan B is acceptable, and this is different than taking it regularly (daily) as a form of birth control which we’ll discuss below. 

Can you take Plan B One-Step instead of regular birth control?

No, Plan B is not intended for routine use instead of a regular form of birth control. The American College of Obstetrics and Gynecology (ACOG) does not recommend using emergency contraception (levonorgestrel pills) for long-term contraception because these pills expose you to repeated higher levels of hormones than you would receive if you used regular birth control pills. Also, frequent use of emergency contraception may lead to an increased incidence of side effects, including menstrual disturbances.

What are the side effects of Plan B emergency contraception?

Taking emergency contraception pills affects hormone levels in the body, which can cause side effects. Women experience common side effects like heavier menstrual bleeding, irregular bleeding, nausea, lower abdominal pain, fatigue, breast tenderness, headache, and dizziness. 

What are some other options for morning after pills?

Ella emergency contraception or a copper IUD may be more effective than Plan B in overweight or obese women (BMI over 30). If you are looking for long-term alternatives, a copper IUD called Paragard can prevent pregnancy if inserted within 5 days of unprotected sex. Once it is in place, Paragard offers 99.9% protection against pregnancy for 10 years. 

Wrapping Up: Plan B Emergency Contraception

  • When taken correctly, Plan B One-Step is 87-89% effective in preventing an unplanned pregnancy.
  • You only have to take one pill after unprotected sex or failure of regular birth control.
  • The sooner you take Plan B, the more effective it is. This emergency contraceptive works best if it is taken within 72 hours (3 days) after unprotected sex. However, you can take it up to five days after unprotected sexual intercourse.
  • Do not use Plan B  as a form of regular contraception.
  • Do not take Plan B in case of a known or suspected pregnancy. This pill will not terminate or abort an existing pregnancy.
  • Do not take levonorgestrel (Plan B) if you have already taken Ella morning-after pill since your last menstrual period.
  • Plan B One-Step can affect the expected date of your next period. If your menses are more than a week late, you may be pregnant. Do a home pregnancy test or consult a healthcare professional at a family planning clinic such as Planned Parenthood. 
  • Plan B One-Step does not protect you against sexually transmitted infections or HIV
  • If you vomit within 2 hours of taking Plan B, consult a healthcare provider before taking a second dose.
  • If you develop severe abdominal pain within 3-5 weeks of taking one dose of Plan B One-Step, contact your doctor immediately. You may have an ectopic pregnancy where the fertilized egg has attached outside the uterus. An ectopic pregnancy is a potentially life-threatening condition and requires emergency medical care. 


  1. https://www.mayoclinic.org/tests-procedures/morning-after-pill/about/pac-20394730
  2. https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/021998lbl.pdf