There is no medical limit on how many times you can take Plan B. It is not dangerous to use it more than once, and taking it multiple times will not harm your fertility or cause serious health problems. That said, it’s not designed to be your regular method of birth control, and there are practical reasons why relying on it repeatedly is a bad strategy.
No Set Maximum, but It’s Not Routine Birth Control
Plan B contains a single dose of a synthetic hormone that works by delaying ovulation. You can take it as many times as you need to after unprotected sex, and there is no known toxic threshold. The FDA states that emergency contraception “is not for routine contraceptive use,” but that’s a recommendation about effectiveness, not a safety warning. Taking it twice in one week or several times in a year won’t cause organ damage or long-term fertility problems. A review published in the journal Contraception found no evidence of increased miscarriage risk or disrupted menstrual cycles in people who used it repeatedly.
The real issue is that Plan B is significantly less reliable than regular birth control. It’s 81 to 90% effective depending on when you take it, compared to over 99% for an IUD. Every time you rely on Plan B instead of a consistent method, you’re accepting worse odds.
What Happens to Your Body With Repeated Use
Side effects from a single dose are generally mild: nausea, headache, breast tenderness, dizziness. These typically resolve within a day or two. The more noticeable consequence of frequent use is what it does to your menstrual cycle. Using emergency contraception often can make your periods irregular or unpredictable, and a single dose can delay your period by up to a week. If you’re taking it multiple times in a cycle, tracking your period becomes nearly impossible, which makes it harder to know whether the pill actually worked.
None of these effects are medically dangerous. They’re just inconvenient and stressful, especially when you’re already anxious about a possible pregnancy.
Taking Two Doses Close Together
If you had unprotected sex, took Plan B, and then had unprotected sex again a day or two later, taking a second dose is reasonable. Each dose works by delaying ovulation for that specific window, and the hormone clears your system quickly. You won’t “overdose” on it. Even in cases of accidental overdose of hormonal birth control pills, symptoms are limited to things like nausea, headache, and heavier bleeding. Serious complications are very unlikely.
One important thing to know: if you already ovulated before taking Plan B, the pill won’t stop a pregnancy from that cycle. Taking extra doses won’t fix that. Plan B does not interrupt a pregnancy that has already begun.
Effectiveness Drops Fast
Timing matters far more than dose count. Plan B is about 94% effective when taken within the first 24 hours after unprotected sex. By 72 hours, that drops to roughly 58%. After three days, the standard levonorgestrel pill is not recommended at all.
If you’re past the 72-hour window, a prescription option called ella (ulipristal acetate) works up to five days after sex and stays around 85% effective at the 120-hour mark. A copper IUD placed within five days is the most effective emergency option at 99%, and it doubles as long-term birth control for up to 10 years.
Weight Affects How Well It Works
If you weigh more than 165 pounds, Plan B may not work as well. This doesn’t mean it’s useless, but the effectiveness drops enough to consider alternatives. Ella remains effective at higher weights, though it also loses reliability above 195 pounds. The copper IUD works regardless of weight and is the strongest emergency option in this situation.
Why Frequent Use Is a Signal to Switch Methods
If you’ve taken Plan B more than once or twice in recent months, that’s worth paying attention to, not because of safety concerns, but because it suggests your current approach to contraception isn’t working for you. Plan B costs $11 to $50 per dose, adds up quickly, and protects you less effectively each time compared to a consistent method.
Long-acting reversible contraception, like an IUD or a hormonal implant, has the lowest failure rate of any method and requires no day-to-day effort. The copper IUD in particular can serve as both emergency contraception (if placed within five days of unprotected sex) and ongoing birth control for years afterward. Hormonal IUDs and arm implants offer similar set-it-and-forget-it reliability. These methods have significantly lower unintended pregnancy rates than oral contraceptives, patches, or condoms alone, largely because there’s no gap in coverage from missed pills or inconsistent use.
If cost or access is a barrier, many clinics offer IUDs and implants on a sliding scale or at no cost through programs like Title X. Planned Parenthood locations are a common starting point.