What is the maximum number of times an 18-year-old female can use Plan B (levonorgestrel) in a month?

Plan B Use Frequency in Adolescents

There is no maximum limit on the number of times Plan B can be used in a month—it can be taken as needed after each episode of unprotected intercourse, though it is not recommended as an ongoing contraceptive method due to lower efficacy compared to regular contraception. 1

Safety and Repeated Use

• Plan B (levonorgestrel 1.5 mg) has no medical contraindications and can be used multiple times without harm. 1, 2
• Levonorgestrel emergency contraception does not have teratogenic or adverse effects on the fetus if inadvertently taken during early pregnancy, and a pregnancy test is not necessary before use. 1, 2
• The medication is safe for repeated use in the same menstrual cycle if multiple episodes of unprotected intercourse occur. 3, 2

Efficacy Considerations

• Levonorgestrel emergency contraception is estimated to be up to 85% effective at preventing pregnancy when used after unprotected intercourse. 1, 2
• Efficacy is highest when taken as soon as possible after unprotected intercourse, though it can be used up to 5 days (120 hours) post-coitum. 1, 4, 5
• The method works primarily by delaying or inhibiting ovulation and does not disrupt an established pregnancy. 1, 2

Important Limitations and Counseling Points

• While safe for repeated use, Plan B should not be used as an ongoing contraceptive method because its efficacy is significantly lower than regular contraceptive methods (85% vs. >99% for LARC methods). 1, 3
• For an 18-year-old female, counseling should include discussion of more effective ongoing contraceptive options, with LARC methods (implant or IUD) as first-line recommendations. 6
• Advance provision of emergency contraception should be part of routine adolescent care to ensure timely access when needed. 1, 6

Weight-Related Efficacy Concerns

• Levonorgestrel emergency contraception loses effectiveness in individuals who weigh more than 165 pounds and may be ineffective in those who weigh more than 176 pounds. 1
• For adolescents above these weight thresholds, ulipristal acetate or copper IUD placement should be considered as more effective emergency contraception options. 1

Common Side Effects

• Expected side effects include nausea, vomiting, headache, breast tenderness, and transient alterations in menstrual bleeding pattern. 3
• These side effects are temporary and do not indicate harm from repeated use. 3, 2