How Effective is Plan B If You Take It the Next Morning?
Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 25th, 2026.
Plan B works best when taken as soon as possible after unprotected intercourse and is intended for use within 72 hours. Taking it the next morning is still within that window, but no single effectiveness percentage applies to everyone because effectiveness depends partly on how soon it is taken and whether ovulation has already begun. Studies show that levonorgestrel, Plan B's active ingredient, works primarily by preventing or delaying ovulation when taken before the luteinizing hormone surge.
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