It is generally safe to combine daily hormonal contraception, often called the pill, with the emergency contraceptive Plan B (levonorgestrel). The daily birth control pill uses low, consistent doses of hormones to prevent ovulation and thicken cervical mucus, offering continuous protection when taken correctly. Plan B contains a single high dose of the progestin levonorgestrel, intended to address a single instance of contraceptive failure or unprotected intercourse. Since both medications use similar hormones, they are compatible, but the hormone surge from Plan B requires careful management of the ongoing pill schedule.
Understanding Emergency Contraception
Plan B One-Step and its generic equivalents are progestin-only emergency contraceptive pills that work primarily by preventing or delaying ovulation. The high dose of levonorgestrel temporarily suppresses the luteinizing hormone (LH) surge, which triggers the release of an egg from the ovary. If ovulation is prevented, fertilization cannot occur.
The effectiveness of levonorgestrel is highly time-sensitive. It is most effective when taken as soon as possible after unprotected sex, ideally within 72 hours (three days). While some evidence suggests it may have an effect up to 120 hours (five days), efficacy declines significantly the longer the wait. Plan B is a single-event intervention that prevents pregnancy from starting; it is not the same as the abortion pill (mifepristone).
Immediate Instructions for Use
If you are currently taking a daily hormonal birth control pill and need to use Plan B due to a missed dose or contraceptive failure, take the emergency contraceptive as quickly as possible. The sooner levonorgestrel is introduced, the greater its chance of success in inhibiting ovulation. Swallow the Plan B tablet immediately upon obtaining it.
After taking Plan B, continue your regular daily birth control pill regimen on its normal schedule. Do not stop taking your daily pill, even for a single day, as this increases the risk of ovulation and compromises ongoing protection. Missing subsequent doses would counteract the protective effect of Plan B.
This continuation applies regardless of the reason for using Plan B (e.g., missed pill or broken condom). The high dose of levonorgestrel will not reduce the effectiveness of your regular pill pack. Maintaining the daily schedule is necessary to restore your usual level of contraceptive protection.
Ensuring Continued Protection
Taking Plan B introduces a large surge of hormones that can temporarily disrupt the protective mechanism of the regular daily pill. Since Plan B only addresses the single incident that prompted its use, it does not offer continuous protection afterward. The user remains vulnerable to pregnancy from any subsequent unprotected intercourse until the regular birth control pill’s efficacy is fully restored.
To ensure ongoing protection, use a backup barrier method, such as condoms, for the next seven consecutive days of correctly taking active daily birth control pills. After taking seven active hormonal pills in a row, hormone levels are typically sufficient to suppress ovulation again, and you can rely solely on the daily pill. This backup contraception bridges the gap until the daily regimen has re-established its full effectiveness.
Expected Physical Reactions
The sudden, high concentration of hormones from Plan B, combined with the hormones from the daily pill, causes temporary physical reactions. Common side effects include nausea, headache, dizziness, and breast tenderness. These symptoms typically subside within 24 to 48 hours after ingestion.
If you vomit within two hours of taking the Plan B tablet, contact a healthcare provider, as a second dose may be needed to ensure absorption. The high hormone dose also frequently causes changes to the menstrual cycle, leading to irregular bleeding or spotting in the days following use. Your next scheduled period may be delayed, come earlier, or be lighter or heavier than usual. If your period is delayed by more than one week past its expected start date, take a pregnancy test.