Medically reviewed by Veronica Hackethal | MD, MSc, Harvard University | University of Oxford | Columbia Vagelos College of Physicians and Surgeons on March 9th, 2026.
Emergency contraception can prevent pregnancy up to 72 hours after unprotected intercourse
Plan B One-Step is 95% effective when taken within 24 hours
The medication works by preventing or delaying ovulation
Side effects are typically mild and short-term
Emergency contraception provides women with a crucial option for preventing unintended pregnancy. Plan B One-Step offers a safe, accessible method to reduce pregnancy risk after contraceptive failure or unprotected sexual encounters. Birth control interactions can be complex, which makes understanding emergency contraception more important than ever.
Modern reproductive health demands informed choices, and Plan B One-Step represents an important tool in birth control options. The medication provides a critical window of opportunity for pregnancy prevention, offering women additional reproductive autonomy and peace of mind.
The medication contains 1.5 milligrams of levonorgestrel, a synthetic hormone that primarily prevents ovulation. By stopping the ovaries from releasing an egg, Plan B dramatically reduces the chance of fertilization. Side effects of levonorgestrel are generally mild and temporary, making it a reliable emergency contraception option.
The mechanism of action involves multiple strategies. Beyond preventing ovulation, the medication can also thicken cervical mucus, making it more challenging for sperm to reach a potential egg. It's important to understand that Plan B is not an abortion pill and will not terminate an existing pregnancy.
Effectiveness is highly time-sensitive. When taken within 24 hours, Plan B is approximately 95% effective. This drops to around 85% between 25-48 hours and further reduces to about 58% between 49-72 hours after unprotected intercourse.
Key factors influencing effectiveness include:
Proximity to ovulation
Individual hormonal variations
Timing of medication intake
Most women tolerate Plan B One-Step well. Common side effects include:
Temporary menstrual cycle changes
Mild nausea
Slight fatigue
Potential headaches
Side Effect |
Frequency |
Duration |
|---|---|---|
Nausea |
14% of users |
1-2 days |
Menstrual Changes |
Common |
1-2 cycles |
Fatigue |
Moderate |
24-48 hours |
Always consult healthcare professionals for personalized advice. Plan B is not recommended for routine contraception but serves as an emergency option. Women should consider follow-up pregnancy testing if their next period is significantly delayed.
Yes, it's generally safe for most women when used as directed.
While possible, it's not recommended as a regular contraception method.
Some studies suggest potential reduced efficacy in women over 165 pounds.
As soon as possible after unprotected intercourse, ideally within 24 hours.
No, it only prevents pregnancy and does not protect against sexually transmitted infections.
Care you can trust. Doctronic is clinically validated with 99% treatment plan alignment.
What an Anxiety Attack Actually IsAn anxiety attack is a sudden episode of intense anxiety or fear accompanied by physical symptoms including racing heart, shortness of [...]
Read MoreWhy People Look Beyond PrescriptionsDepression is one of the most common mental health conditions in the United States. About 67% of adults who experienced a major depressive [...]
Read MoreDepression Is Not a Linear ProgressionDepression does not progress through a fixed, predictable sequence of stages the way some medical conditions do. The term [...]
Read More
Join 50,000+ readers using Doctronic to understand symptoms, medications,
and next steps.
Add your phone number below to get health updates and exclusive VIP offers.
By providing your phone number, you agree to receive SMS updates from Company. Message and data rates may apply. Reply “STOP” to opt-out anytime. Read our Privacy Policy and Terms of Service for more details.
Save your consults. Talk with licensed doctors and manage your health history.
