Strengths of Plan B

Plan B® (levonorgestrel) is an emergency contraceptive used to prevent pregnancy in women who have had unprotected sex. In the past, there were two strengths for Plan B, including:
  • Original Plan B, with 0.75 mg of levonorgestrel per tablet, in a pack that contains two tablets
  • Plan B One-Step™, with 1.5 mg of levonorgestrel per tablet, in a pack that contains one tablet.
However, the original (two-step) product has been discontinued, as it has been replaced by the new one-step product. A generic version of the two-step product (sold under the name Next Choice®) is still available.

For original Plan B, the first tablet should be taken as soon as possible within 72 hours (three days) after unprotected sex. The second tablet should be taken 12 hours after the first tablet, even if this means taking it in the middle of the night. For the new Plan B One-Step, only a single dose is taken. The sooner you take Plan B, the more effective it is at preventing pregnancy.

Plan B prevents pregnancy primarily by stopping ovulation (the maturation and release of eggs from the ovaries) or by preventing fertilization of the egg if ovulation has already occurred. It also alters the lining of the uterus (the endometrium), making it less receptive to a fertilized egg. If a fertilized egg has already implanted into the uterus, Plan B will not cause an abortion.
(Click Plan B and Plan B Dosage for a more in-depth look at the strengths of Plan B birth control pills. These articles also discuss potential side effects, general dosing guidelines, and important information to be aware of before using this medication.)
Last reviewed by: Kristi Monson, PharmD
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