Plan B (levonorgestrel): How it works and when to take it

If you’ve had a condom break or unprotected sex, Plan B works best the sooner you take it—ideally within 24 hours, still helpful up to 72 hours, and sometimes up to 5 days, though effectiveness drops over time. It mainly delays ovulation, is less reliable if you’re already ovulating or at a higher body weight, and can temporarily mess with your period and cause short‑term side effects like nausea or spotting. Here’s how timing, BMI, and cycle phase change your odds, what symptoms are normal, when to test for pregnancy, and when to talk to a doctor or consider options like ella or a copper IUD.