There is no medical limit on how many times you can take Plan B in your lifetime. No health organization sets a maximum number, and the available research does not show that repeated use causes lasting harm to your health or fertility. That said, Plan B is less effective at preventing pregnancy than regular birth control methods, and frequent use can temporarily disrupt your menstrual cycle, which is why it’s designed as a backup rather than a primary method.
Why There’s No Official Limit
Plan B contains a single dose of a synthetic hormone that is also found in many daily birth control pills, just at a higher concentration. It works primarily by delaying or preventing ovulation. Because the hormone clears your system quickly, taking it multiple times doesn’t create a buildup or cause cumulative damage to your organs.
A systematic review published in BMJ Sexual & Reproductive Health examined the safety of repeated emergency contraceptive pill use and found no evidence of serious safety concerns. No studies in the review reported cases of blood clots, hospitalization, or hemorrhage linked to repeated use. The researchers did note that the overall certainty of evidence was very low simply because few large studies have been conducted, not because red flags were found. Even in cases where women took multiple doses in a single menstrual cycle, studies tracking pregnancy and infant outcomes (weight, height, head circumference, developmental scores) found no differences between higher-dose and lower-dose groups at follow-ups through 24 months.
What Repeated Use Does to Your Cycle
The most noticeable effect of taking Plan B more than once is disruption to your period. Each dose can delay your next period by up to a week, and you may experience spotting or heavier bleeding between cycles. These side effects are temporary and typically resolve within a few days, but if you’re using Plan B frequently, the irregularity can stack up and make it harder to track your cycle or know if the pill worked.
If your period doesn’t arrive within three weeks of taking Plan B, take a pregnancy test. And if you experience heavy bleeding with abdominal pain or ongoing irregular spotting, that warrants a call to your doctor.
One Potential Risk Worth Knowing
The BMJ review did flag one finding: among women who became pregnant after using Plan B in the same cycle it failed, those with an ectopic pregnancy (where a fertilized egg implants outside the uterus) had about 2.5 times higher odds of having used Plan B repeatedly in that cycle compared to women with normal pregnancies. This doesn’t mean Plan B causes ectopic pregnancies, but it suggests that if the pill fails after repeated use, the risk of an ectopic pregnancy may be slightly elevated. Ectopic pregnancies are a medical emergency, so knowing the signs (sharp abdominal pain, dizziness, vaginal bleeding) matters if you’ve taken Plan B multiple times recently and suspect the pill didn’t work.
It Works, but Not as Well as Regular Birth Control
Plan B prevents pregnancy in roughly 87% to 90% of cases when taken within 72 hours of unprotected sex. That number drops to 72% to 87% if taken between 72 and 120 hours. By comparison, consistent use of daily oral contraceptives, an IUD, or an implant prevents pregnancy at rates above 99% for some methods. Relying on Plan B repeatedly means accepting a significantly higher chance of an unintended pregnancy over time compared to using a regular method.
Timing matters a lot. The pregnancy rate in clinical trials was 0.8% when women took levonorgestrel within 72 hours and 1.8% in the 72 to 120 hour window. Every hour you wait reduces effectiveness.
Body weight also plays a role. If you weigh more than 165 pounds, levonorgestrel-based emergency contraception like Plan B becomes less effective. A copper IUD, which can be inserted up to five days after unprotected sex, is the most effective emergency option regardless of weight.
Switching to a Regular Method
If you’ve found yourself reaching for Plan B more than once or twice, that’s a signal to explore a method that works continuously rather than after the fact. The good news is you don’t have to wait long after taking Plan B to start something new.
Condoms can be used immediately. Oral contraceptive pills, the patch, or the vaginal ring can also be started right away after taking levonorgestrel-based emergency contraception, though you’ll need a backup method like condoms for the first seven days. A copper IUD can even double as emergency contraception if inserted within five days of unprotected sex, and then it continues protecting you for up to 10 years.
If you took a different type of emergency contraceptive pill containing ulipristal acetate (sold as ella), the timeline is slightly different. You should wait six days before starting any hormonal method, because the progestin in hormonal contraception can interfere with ulipristal’s effectiveness and vice versa.
Plan B costs between $30 and $50 per dose and is available without a prescription. Many regular contraceptive methods are covered by insurance with no out-of-pocket cost, making them both more effective and more affordable over time.