There is no medical limit on how many times you can take Plan B. The American College of Obstetricians and Gynecologists states that oral emergency contraception can be used more than once, even within the same menstrual cycle. It won’t harm your health or affect your future ability to get pregnant. That said, it’s not designed to be your go-to birth control, and there are practical reasons to switch to something more reliable if you’re reaching for it often.
No Maximum Number of Uses
Plan B contains a single dose of a synthetic hormone that works by delaying or preventing ovulation. Taking it multiple times doesn’t cause it to build up in your body or create lasting hormonal changes. Each dose is processed and cleared relatively quickly. Your fertility returns to normal afterward, and repeated use has no effect on your ability to conceive in the future.
You can take it more than once in the same cycle if needed. However, if you need emergency contraception again within five days of a previous dose, stick with Plan B or another levonorgestrel pill rather than switching to a different type (ella/ulipristal acetate). Using both types close together can interfere with how well either one works.
Why It’s Not Ideal as Regular Birth Control
Plan B is less effective than almost every form of regular contraception. Studies report a pregnancy rate of 1.4 to 2.6% per use with emergency contraceptive pills, which sounds low for a single event but adds up fast if you’re relying on it month after month. Compare that to an IUD, which has a failure rate closer to 0.3%.
There’s also the timing problem. Plan B only works if taken before ovulation. Once your body has already released an egg, the pill does essentially nothing. The pregnancy rate after taking it post-ovulation is the same as if you hadn’t taken it at all. Since most people don’t know exactly when they ovulate, every use is something of a gamble, and that gamble gets worse the longer you wait. Regular contraception removes that uncertainty.
Cost is another factor. A single box of Plan B runs $30 to $50, while many forms of ongoing birth control are covered by insurance or available at lower monthly costs.
Side Effects With Repeated Use
A single dose of Plan B causes mild side effects for most people: nausea, headache, fatigue, breast tenderness, and cramping. These typically resolve within a day or two. Your next period may arrive earlier or later than expected, be heavier or lighter than usual, or come with some spotting beforehand.
When you take Plan B frequently, these cycle disruptions can stack up and make your periods unpredictable. You might get breakthrough bleeding between periods or lose track of your normal cycle timing entirely. None of this is dangerous, but it can be stressful, especially if irregular bleeding makes you worry about whether the pill actually worked. An unpredictable cycle also makes it harder to identify a missed period, which is the most obvious early sign of pregnancy.
Weight Can Affect How Well It Works
Plan B becomes less effective if you weigh more than 165 pounds. The hormone dose in the pill was designed for a narrower weight range, and at higher body weights, it may not suppress ovulation as reliably. If this applies to you and you need emergency contraception, a copper IUD inserted within five days of unprotected sex is roughly ten times more effective than emergency contraceptive pills and works regardless of weight. A hormonal IUD placed as emergency contraception has shown a pregnancy rate of just 0.3% in clinical studies.
Switching to Ongoing Contraception
If you’ve taken Plan B more than once or twice, that’s a reasonable signal to explore a method you don’t have to think about in the moment. You can start most forms of hormonal birth control, including the pill, patch, or ring, immediately after taking Plan B. You’ll need to use a backup method like condoms for the first seven days while the new contraception takes effect.
An IUD is another option. Both copper and hormonal IUDs can be placed shortly after emergency contraception use, as long as pregnancy has been ruled out. The copper IUD has the added advantage of doubling as emergency contraception itself if placed within five days of unprotected sex, then continuing to prevent pregnancy for up to ten years. Unlike pills that require a narrow timing window relative to ovulation, IUDs work through a different mechanism and provide immediate, ongoing protection once they’re in place.