There is no medical limit on how often you can take Plan B. You can use it multiple times in the same month, the same cycle, or the same year without long-term health consequences. That said, it’s designed as a backup, not a routine method, and there are practical reasons to consider other options if you’re reaching for it frequently.
No Maximum Number of Times
Plan B (levonorgestrel) is safe to take as many times as you need it. According to Planned Parenthood, taking the morning-after pill multiple times doesn’t reduce its effectiveness and won’t cause long-term side effects. The World Health Organization confirms that levonorgestrel emergency contraception works by delaying ovulation, does not cause abortion, and cannot harm an existing pregnancy.
So if you’ve already taken it once this month and need it again, you can. There’s no waiting period between doses. Each dose works independently by temporarily delaying the release of an egg.
Why It’s Not Ideal as a Regular Method
Even though it’s safe to repeat, Plan B is less effective than almost every standard birth control method. It prevents roughly 81% to 90% of pregnancies when taken within 72 hours of unprotected sex. Compare that to daily birth control pills, which prevent over 99% of pregnancies when used correctly. An IUD is even more reliable.
Timing matters a lot with Plan B. If you take it within the first 24 hours, effectiveness is around 94%. By the 72-hour mark, it drops to about 58%. So each time you rely on it, you’re accepting a much bigger margin of risk than you would with ongoing contraception.
Cost adds up too. A single dose of Plan B or its generics runs $10 to $50 over the counter. If you’re using it several times a year, that can easily surpass the cost of a monthly prescription or a one-time IUD placement.
Side Effects From Repeated Use
Plan B delivers a large dose of the same hormone found in many daily birth control pills, just at a much higher concentration. That hormonal surge is what delays ovulation, but it also commonly disrupts your menstrual cycle. You might get your period a week early, a week late, or experience spotting between periods. Your flow can be heavier or lighter than normal.
These changes are temporary and resolve on their own, but if you’re taking Plan B multiple times in a short window, you may find your cycle unpredictable for a while. That unpredictability can make it harder to track ovulation or know whether the pill worked, which creates its own stress. Nausea, fatigue, headaches, and breast tenderness are also common short-term side effects, and they’ll recur with each dose.
Weight Can Affect How Well It Works
One factor many people don’t know about: Plan B becomes significantly less effective at higher body weights. Research from Oregon Health & Science University found that people with a BMI of 30 or above experienced morning-after pill failure four times as often as those with a BMI under 25. Blood levels of the drug were about 50% lower in higher-BMI individuals after a standard dose, meaning the hormone likely never reaches the concentration needed to block ovulation.
Doubling the dose doesn’t solve this. A study published in Obstetrics & Gynecology found that taking two Plan B pills was not more effective for people with a BMI over 30. If this applies to you, a copper IUD inserted within five days of unprotected sex is the most reliable emergency option, and it also works as long-term contraception afterward. Ella (ulipristal acetate), a prescription-only morning-after pill, maintains better effectiveness at higher weights than Plan B, though it still has limits.
When Switching to Regular Birth Control Makes Sense
If you’ve taken Plan B more than once or twice in the past few months, that’s a signal your current approach to preventing pregnancy isn’t matching your actual needs. That’s not a judgment. It’s just a practical observation that a daily pill, a patch, a ring, an implant, or an IUD would give you far better protection with fewer side effects per month and lower cost over time.
You can start most forms of hormonal birth control immediately after taking Plan B. The emergency dose doesn’t interfere with beginning a regular method. If you take Plan B and then start the pill the next day, you’ll need backup protection (like condoms) for the first seven days until the daily pill reaches full effectiveness.