Generic Plan B contains the same active ingredient, in the same dose, as brand-name Plan B One-Step: 1.5 mg of levonorgestrel in a single tablet. The FDA currently lists 11 generic versions with active marketing status, and each one must meet the same bioequivalence standards before it can be sold. The meaningful difference is price, not what’s inside the pill.
What the FDA Requires From Generics
To gain approval, a generic levonorgestrel product must pass a single-dose crossover bioequivalence study conducted in healthy, non-pregnant, non-lactating women under fasting conditions. The study compares plasma levels of levonorgestrel between the generic and the brand-name reference product. The generic must fall within a 90% confidence interval of the brand’s absorption profile, meaning the body takes it in at essentially the same rate and to the same extent.
Generic manufacturers also have to match the brand-name labeling, with only minor permitted differences like the product name and packaging design. If the FDA updates the labeling for Plan B One-Step, generic holders are expected to update theirs accordingly. The inactive ingredients (binders, fillers, coatings) can differ between products, which is why a generic pill might look different in size, shape, or color. But these inactive ingredients don’t change how the drug works.
How the Pill Works
Levonorgestrel is a synthetic form of progesterone. Its primary role in emergency contraception is disrupting or delaying ovulation, the release of an egg from the ovary. If ovulation hasn’t happened yet, the drug can interfere with follicle development enough to prevent or alter egg release. Research shows this effect is strongest when the pill is taken well before ovulation. If taken very close to ovulation (within about two days), the drug has a much more limited ability to stop the process.
This is true for both the brand-name and every generic version, because they all deliver the same compound at the same dose.
Effectiveness Drops Fast With Delay
Timing matters far more than which brand you buy. When taken immediately after unprotected sex, levonorgestrel’s maximum effectiveness is around 91%. That number drops sharply: to roughly 61% after one day, 28% after two days, and just 19% after three days. The 72-hour window you see on the packaging represents the outer limit, not the sweet spot. Every hour counts.
This steep decline is another reason the price difference between generic and brand-name products matters. If a generic version is available right now and Plan B One-Step isn’t, the cheaper option taken sooner will outperform the brand-name version taken later.
Weight Can Affect How Well It Works
One factor that applies equally to all levonorgestrel products is body weight. A pooled analysis of four large studies found that women with a BMI under 25 had a pregnancy rate of about 1.3% after taking the pill. For women with a BMI between 25 and 30 (overweight), the rate rose to 2.5%. For women with a BMI over 30 (obese), it climbed to 5.8%, a statistically significant reduction in effectiveness.
This isn’t a reason to skip levonorgestrel emergency contraception if it’s what you have access to, but it’s worth knowing. A copper IUD placed within five days of unprotected sex is the most effective emergency contraceptive regardless of weight, and some non-levonorgestrel pill options may also work better at higher body weights.
Side Effects Are the Same
Because the active ingredient and dose are identical, so is the side effect profile. The most commonly reported effects include nausea, headache, abdominal pain, dizziness, breast tenderness, fatigue, and vomiting. Changes in your next period are also common: it may arrive earlier or later than expected, and bleeding can be heavier or lighter than usual. Diarrhea is a less common side effect. These effects are generally short-lived and resolve on their own.
Price and Availability
This is where generics have a clear advantage. Brand-name Plan B One-Step typically costs between $42 and $50 at major pharmacies. Generic versions range from about $11 to $50 depending on the retailer and specific product. Names you may see on shelves include Take Action, My Way, AfterPill, and several store-brand options. All contain the same 1.5 mg levonorgestrel tablet.
Every single-dose levonorgestrel emergency contraceptive, brand or generic, is available over the counter with no age restriction, no ID requirement, and no need to ask at the pharmacy counter. They can be stocked on regular store shelves alongside other family planning products. You can also order them online.
Bottom Line: Same Drug, Lower Price
Generic Plan B is pharmacologically the same as Plan B One-Step. The FDA requires identical active ingredients, identical dosing, and proven bioequivalence before any generic reaches the shelf. The only differences are cosmetic (pill appearance, packaging) and financial. If you’re choosing between a $12 generic and a $50 brand-name box, the generic gives you the same protection at a fraction of the cost.