Plan B can delay your period by up to one week. Most people find their period arrives within a few days of when they expected it, but a delay of anywhere from one to seven days is normal after taking emergency contraception. Your cycle should return to its regular pattern the following month.
Why Plan B Shifts Your Cycle
Plan B contains a synthetic hormone called levonorgestrel, and its primary job is to stop or delay your ovary from releasing an egg. If ovulation gets pushed back by a few days, everything downstream in your cycle shifts too. Your body still needs to go through the same hormonal sequence after ovulation before your period starts, so a delayed egg release means a delayed period.
The size of the delay depends largely on where you are in your cycle when you take the pill. If you take Plan B early in your cycle, well before ovulation, you’re more likely to notice a longer delay because there’s more room for the timeline to shift. If you take it closer to when you were already about to ovulate, your period may arrive right on time or even a day or two early.
Spotting vs. Your Actual Period
Many people notice light bleeding a few days after taking Plan B and wonder if that counts as their period. It doesn’t. This spotting is a response to the sudden dose of hormones, not a true menstrual bleed. It’s usually very light, just a few spots on your underwear or toilet paper, and the color can range from pink to red to brown. You’re unlikely to have cramps or other typical period symptoms with this spotting, and a panty liner is plenty of protection.
When your actual period does arrive, it should feel like a normal period with your usual flow and cramps. Some people find the first period after Plan B is slightly lighter or heavier than usual, but this variation is temporary.
When a Late Period Means You Should Test
A delay of a few days is expected and not a reason to worry. But if your period hasn’t arrived within three weeks of taking Plan B, a pregnancy test is a smart next step. Home pregnancy tests are most reliable starting on the first day of your missed period. If you’re unsure when your period was due, test at least 21 days after you last had unprotected sex.
Keep in mind that Plan B is not 100% effective. Its ability to prevent pregnancy decreases the longer you wait to take it after unprotected sex, and research shows that effectiveness also decreases at higher body weights. If your period is more than a week late and you have any early pregnancy symptoms like breast tenderness, nausea, or fatigue, testing sooner rather than later gives you more options.
What to Expect in the Following Months
For most people, the cycle after taking Plan B returns completely to normal. Your next period should arrive on its usual schedule with its usual flow. Occasional use of emergency contraception is unlikely to cause lasting changes to your cycle. Repeated use, however, can make your periods less predictable over time, so it’s not ideal as a regular form of birth control.
If you find yourself relying on Plan B more than once or twice, that’s a good signal to explore a routine contraceptive method that won’t disrupt your cycle each time. Long-acting options like IUDs or hormonal implants are more effective at preventing pregnancy and won’t cause the same month-to-month irregularity.