How Does Plan B (the Morning After Pill) Work?
- Your Options Medical
- Jul 18, 2025
- 2 min read
Updated: Jul 30, 2025
If you’ve recently had unprotected sex or experienced birth control failure, you may be looking for more information on morning-after pills and emergency contraception to prevent a possible pregnancy.
Learn more about the different types of emergency contraceptives, how they work, and what they do.
Note: If you are already experiencing pregnancy symptoms, make an appointment today for free testing and explore your options.
How do emergency contraceptives work?
Emergency contraceptives are intended to delay or prevent ovulation. Ovulation is the release of an egg from your ovaries. If there is no egg for the sperm to fertilize, no pregnancy can occur. However, this does not mean that they are guaranteed to stop pregnancy. If you were already ovulating at the time of unprotected sex, the medication will try to prevent fertilization.
What are the most common side effects of emergency contraceptives?
Common side effects can include:
Nausea or vomiting
Headaches
Abdominal pain
Tiredness (fatigue)
Dizziness
Breast pain
Spotting (bleeding in between periods)
Heavier menstrual bleeding
Emergency contraceptives can also cause a miscarriage or pregnancy complications if you are already pregnant.
Other factors like BMI (body mass index) are important to consider when taking medications, particularly emergency contraceptives. Side effects can vary in intensity; no two people react to things the same.
Using emergency contraceptives may delay your period by up to one week. If you do not get your period within three to four weeks of taking emergency contraceptives, a pregnancy test is needed to determine if you are pregnant.
Are morning-after pills and 5-day-after pills the same?
The morning-after pill comes in two main forms that use different ingredients. There are name-brand and off-brand emergency contraceptives, but the most common type is FDA-approved up to three days after sex. The 5-day pill requires a doctor's prescription.
Before taking any emergency contraceptive, it’s important to talk to a nurse or licensed medical professional about ingredients, side effects, and how they are used.
What if I am already pregnant when I take an emergency contraceptive?
Emergency contraception can prevent a fertilized egg from attaching inside your uterus (implantation). If fertilization and implantation have already happened, emergency contraception will not interrupt the pregnancy.
Where can I get more information about emergency contraception?
While there are many credible sources available online about emergency contraceptives, there is an equal amount of misinformation. Sifting through myths and facts can be difficult.
Because every woman is different, we recommend, before you buy Plan B, coming in and talking with one of our advocates to get more information about emergency contraceptives and your options. If needed, you can also talk with a nurse about your health history and possible side effects.
Your Options Medical is here to help you navigate the road ahead and give you the information you need to make an informed and empowered choice. We provide confidential, cost-free services for women in Revere, MA.
Sources:
Contraception | CDC. (n.d.). https://www.cdc.gov/reproductivehealth/contraception/index.htm#:~:text=Emergency%20contraception%20is%20NOT%20a,five%20days%20of%20unprotected%20sex.
Plan B One-Step (Morning-After Pill): How it Works, Side Effects. (n.d.). Drugs.com. https://www.drugs.com/plan-b.html
Ella Morning After Pill (Emergency Contraception) guide. (n.d.). Drugs.com. https://www.drugs.com/ella.html
