There is no maximum number of times you can take Plan B in your life. No medical organization, including the FDA and the World Health Organization, sets a lifetime cap on emergency contraception use. You can take it whenever you need it, and repeated use does not cause long-term health consequences or affect your future fertility.
That said, there are practical reasons why Plan B works better as a backup than a go-to method. Here’s what actually happens in your body when you use it, why frequency matters for effectiveness, and what to know if you’ve taken it more than once.
No Lifetime Limit Exists
The FDA labeling for Plan B One-Step does not specify a numerical limit on how many times you can take it, whether per cycle, per year, or per lifetime. It simply states the pill is “a backup method of preventing pregnancy” and “should not be used as regular birth control.” That language is about effectiveness, not safety. Planned Parenthood puts it plainly: “It’s totally safe to take the morning-after pill as many times as you need to.”
The World Health Organization echoes this, stating that repeated use “poses no known health risks.” The one exception is for people who have medical conditions that make hormonal contraceptives risky for them specifically, such as certain clotting disorders or hormone-sensitive conditions. If you’ve been told by a doctor that combination or progestin-only birth control isn’t safe for you, the same caution may apply to emergency contraception.
Why It Won’t Hurt Your Fertility
One of the most persistent fears about taking Plan B multiple times is that it could make it harder to get pregnant later. This is a myth. The WHO has specifically addressed claims linking emergency contraception to infertility, calling them “factually incorrect.” Levonorgestrel, the hormone in Plan B, does not damage your reproductive system. There is no delay in the return to fertility after taking it.
Plan B works primarily by delaying or preventing ovulation. When you take it before your body releases an egg, the hormone disrupts the normal hormonal surge that triggers ovulation. It can also thicken cervical mucus, making it harder for sperm to reach an egg. These effects are temporary. Once the dose clears your system, your cycle resumes its normal pattern, typically within one to two cycles.
Side Effects of Frequent Use
While Plan B is safe to take repeatedly, using it often can make side effects more noticeable. The WHO notes that frequent use “can result in increased side effects, such as menstrual irregularities.” Common short-term side effects include nausea, fatigue, light bleeding between periods, and heavier or lighter menstrual flow than usual. These typically resolve on their own within a few days.
A single dose can delay your next period by up to a week. If you’re taking Plan B multiple times in the same cycle or across consecutive cycles, your period timing can become unpredictable for a while. This isn’t dangerous, but it can be stressful, especially if you’re watching for signs of pregnancy. If your period is more than a week late after taking Plan B, a pregnancy test is a reasonable next step.
Taking It More Than Once in a Cycle
Some people wonder whether taking Plan B twice in the same menstrual cycle is safe or whether it cancels out the first dose. A systematic review published in BMJ Sexual & Reproductive Health looked at this question and found no evidence of safety concerns with repeated use in the same cycle. Researchers compared outcomes in people exposed to higher cumulative doses of levonorgestrel against those who took lower doses, and pregnancy, fetal, and infant outcomes were similar across groups.
The review concluded that repeated use “should not be discouraged” when multiple instances of unprotected sex occur in the same cycle. Each dose works independently by affecting ovulation and cervical mucus at the time you take it. Taking it again doesn’t undo what the first dose did.
It Works Less Well Than Regular Birth Control
The real reason Plan B isn’t recommended as your primary method isn’t safety. It’s math. Plan B prevents roughly 85% of expected pregnancies when taken within 72 hours. That sounds high, but standard daily birth control pills, IUDs, and implants all have effectiveness rates above 95% with typical use, and some exceed 99%. Over the course of a year, relying on emergency contraception alone leaves you significantly more likely to experience an unintended pregnancy than using almost any routine method.
Plan B is also considerably more expensive per use than monthly birth control. A single dose typically costs between $30 and $50 over the counter. Insurance is required to cover emergency contraception without cost sharing when it’s prescribed, including for advance provision (getting a prescription filled before you need it). But if you’re buying it frequently at retail price, the cost adds up fast compared to methods that are fully covered by most insurance plans.
Weight Can Affect How Well It Works
One factor that matters more than how many times you’ve taken Plan B is your body weight at the time you take it. A pooled analysis of four WHO studies found that people with a BMI over 30 were significantly less likely to have the pill work, with pregnancy odds roughly eight times higher compared to people in lower BMI categories. This doesn’t mean Plan B is useless at higher weights, but the reduction in effectiveness is substantial enough to be worth knowing about.
If your BMI is above 30, a copper IUD inserted within five days of unprotected sex is the most effective form of emergency contraception regardless of weight. Another option is a different emergency contraceptive pill containing ulipristal acetate, which maintains better effectiveness at higher body weights than levonorgestrel, though it still shows some decline.
When Frequent Use Signals a Need for Something Better
If you find yourself reaching for Plan B regularly, that’s not a health emergency, but it is a signal that a more reliable method could make your life easier. Long-acting options like IUDs and implants require no daily action, last for years, and are more effective at preventing pregnancy than any pill you take after the fact. Even if you’ve had trouble with hormonal methods in the past, newer low-dose options or the hormone-free copper IUD may be worth exploring.
Taking Plan B ten times doesn’t make the eleventh time less safe or less effective. But every time you rely on it, you’re accepting a higher failure rate than you’d get from a method designed for ongoing use. The pill itself isn’t the problem. The gap it’s filling is just better filled by something else.