Plan B, a progestin-only emergency contraceptive containing levonorgestrel, helps prevent pregnancy after unprotected sex. Many individuals wonder about its effects on their menstrual cycle, particularly if it might lead to a delayed period.
How Plan B Influences Your Menstrual Cycle
Plan B primarily works by delivering a high dose of levonorgestrel, a synthetic hormone. This significant hormonal surge can prevent or delay the release of an egg from the ovary. By interfering with ovulation, the medication disrupts the natural timing of the menstrual cycle.
The menstrual cycle is regulated by hormones that fluctuate throughout the month. Introducing a large amount of levonorgestrel can temporarily override these natural hormonal signals. This hormonal disruption can cause the subsequent period to start earlier, later, or have different characteristics than usual. The timing of when Plan B is taken relative to ovulation significantly influences its effect on the cycle.
Why Taking Multiple Doses Can Affect Your Period More
Each dose of Plan B introduces a substantial amount of synthetic progestin into the body. When two doses are taken within a short timeframe, the body is exposed to an even higher or more prolonged level of these hormones. This cumulative hormonal impact can lead to a more pronounced or extended disruption of the natural menstrual rhythm.
The body regulates itself based on hormonal cues. A single large dose can temporarily confuse these signals, but repeated exposure amplifies this confusion. This can result in a longer delay of the subsequent period or changes in bleeding patterns (e.g., lighter, heavier, or spotting). The body needs time to process these hormones, and multiple doses extend this adjustment period, potentially leading to more noticeable cycle alterations.
Other Potential Side Effects and When to Consult a Doctor
Beyond affecting the timing of your period, Plan B can cause other temporary side effects. These commonly include nausea, fatigue, headache, breast tenderness, abdominal pain, and dizziness. These side effects typically resolve within a day or two.
Consult a doctor if your period is more than a week late. You should also seek medical advice for severe abdominal pain, unusual or heavy bleeding, or concerns about a potential pregnancy despite taking Plan B. A healthcare professional can provide guidance, rule out pregnancy, and address any persistent symptoms or concerns.