Taking an expired Plan B pill is unlikely to harm you, but it may not work well enough to prevent pregnancy. The active ingredient, levonorgestrel, loses potency over time, meaning an expired pill delivers less of the hormone your body needs to delay ovulation. The biggest risk isn’t a dangerous side effect; it’s that the pill simply fails to do its job when you need it most.
Why Expiration Matters for Plan B
Plan B works by delivering a large dose of a synthetic hormone that delays or prevents the release of an egg from your ovaries. If enough of that hormone has broken down, the pill can’t reliably stop ovulation. Unlike some medications where reduced potency is just an inconvenience, a partially effective emergency contraceptive can mean the difference between preventing a pregnancy and not.
Plan B has a four-year shelf life from the date of manufacture. That expiration date reflects the last point at which the manufacturer guarantees the pill contains its full labeled dose. After that date, the hormone gradually degrades through chemical processes like oxidation and hydrolysis, especially if the pill has been stored in heat or humidity. The tablet itself is thermally stable under normal conditions, but the excipients (inactive filler ingredients like lactose) can absorb moisture, which accelerates breakdown of the active ingredient over time.
Will It Still Prevent Pregnancy?
Even when taken correctly and within the recommended window, Plan B reduces the risk of pregnancy by about 81% to 90%. That already leaves a meaningful failure rate. An expired pill, with reduced hormone levels, pushes that effectiveness lower, but by exactly how much is impossible to say. There are no clinical trials testing how well Plan B works six months or two years past its expiration date, so no one can give you a reliable number.
If your pill expired recently, within a few weeks or even a couple of months, it has likely lost very little potency. A pill that expired a year or more ago is a bigger gamble. The further past the expiration date, the less confidence you can have that it will work. Planned Parenthood’s guidance is straightforward: expired emergency contraception isn’t as effective, and you should check the date to make sure your pill will actually work.
Is an Expired Pill Dangerous?
There is no evidence that expired levonorgestrel becomes toxic or produces new, harmful side effects. The chemical simply degrades into less active compounds. You may still experience the same side effects associated with Plan B, including nausea, headache, fatigue, and changes to your next period. These are caused by the hormone itself, and any amount still present in the pill can trigger them. You will not experience worse or different side effects just because the pill is expired.
What to Do if It’s Your Only Option
If you have unprotected sex and the only Plan B available to you is expired, taking it is better than taking nothing. Some reduced dose of the hormone is still more protective than zero. But treat it as a backup measure, not a guarantee, and look into additional options as quickly as possible.
The most effective emergency contraceptive is the copper IUD, which can be placed by a healthcare provider up to five days after unprotected sex and reduces the risk of pregnancy by more than 99%. A prescription alternative called ella (ulipristal acetate) is also more effective than Plan B when taken between 72 and 120 hours after sex, though it has a shorter shelf life of three years. If you’re within 72 hours, a fresh Plan B from a pharmacy remains the fastest over-the-counter option.
How to Store Plan B So It Lasts
If you keep Plan B on hand for emergencies, where you store it matters. Heat, humidity, and direct sunlight all speed up degradation. A bathroom medicine cabinet, which gets warm and steamy, is one of the worst places. A bedroom drawer or a closet shelf at room temperature is a much better choice. Keep the pill in its original sealed packaging until you need it, since the foil blister pack protects against moisture.
Check the expiration date once or twice a year and replace the pill before it expires. Plan B is available without a prescription at most pharmacies and typically costs between $30 and $50, so rotating your supply every few years is a relatively low-cost way to make sure you’re covered when it counts.