Understanding the Need for Emergency Contraception
Regular birth control pills, whether combination (estrogen and progestin) or progestin-only, are a highly effective method of preventing pregnancy when used correctly [1.2.7]. However, mistakes can happen. Forgetting to take pills, starting a pack late, or experiencing vomiting or diarrhea can compromise their effectiveness, creating a need for a backup method [1.2.4]. This is where emergency contraception (EC), commonly known as the 'morning-after pill,' comes in.
Plan B One-Step and its generic versions contain levonorgestrel, a synthetic hormone (progestin) also found in many birth control pills, but at a much higher dose [1.2.4]. Its primary function is to delay or prevent ovulation, so sperm has no egg to fertilize [1.2.1]. It is most effective when taken within 72 hours of unprotected sex, with efficacy decreasing over time [1.2.2].
Can I take the pill and Plan B at the same time?
Yes, it is considered safe to take levonorgestrel-based emergency contraception like Plan B while also taking your regular birth control pills [1.2.1, 1.3.4]. Plan B does not interact negatively with hormonal contraceptives or make them less effective [1.2.1, 1.5.3].
If you have missed two or more birth control pills and had unprotected sex, taking Plan B is a reasonable step. After taking Plan B, you should resume your regular birth control pill schedule immediately [1.2.5, 1.3.7]. To ensure continuous protection, it is crucial to use a backup barrier method, such as condoms, for the next seven days [1.3.4, 1.4.5]. This is because it takes about seven consecutive days of active pills to re-establish full contraceptive protection.
Potential Side Effects of a Double Dose of Hormones
Because both your regular pill and Plan B contain progestins, taking them together introduces a higher level of hormones into your system. This can lead to more pronounced, though temporary, side effects [1.6.2].
Common side effects include:
- Nausea and vomiting [1.6.3]
- Headaches and dizziness [1.6.4]
- Fatigue [1.6.2]
- Lower abdominal cramping [1.6.3]
- Breast tenderness [1.6.5]
- Changes to your next menstrual period (it may be earlier, later, heavier, or lighter) [1.6.3]
- Spotting or irregular bleeding between periods [1.6.2]
These side effects are generally mild and resolve within a few days or after your next cycle [1.6.3]. If you vomit within two to three hours of taking Plan B, you should contact a healthcare provider, as you may need to take another dose [1.7.6]. If your period is more than a week late, it is recommended to take a pregnancy test [1.6.3].
Important Distinction: Plan B (Levonorgestrel) vs. Ella (Ulipristal Acetate)
It is critical to distinguish between the two main types of morning-after pills, as they interact differently with hormonal birth control.
- Plan B (Levonorgestrel): As discussed, this progestin-based pill is safe to take with your regular birth control pills [1.4.1].
- Ella (Ulipristal Acetate): This is a prescription-only emergency contraceptive that works as a progesterone blocker [1.2.3]. Because it works by blocking the hormones that your birth control pills provide, they can counteract each other, potentially reducing the effectiveness of both the emergency contraceptive and your regular pills [1.7.4].
If you take ella, you must wait at least five days before starting or resuming any hormonal birth control, including the pill, patch, or ring [1.7.2, 1.7.4]. During this five-day waiting period and until your next period, you must use a reliable barrier method like condoms to prevent pregnancy [1.7.2].
Comparison of Emergency Contraception Options
| Feature | Plan B (Levonorgestrel) | Ella (Ulipristal Acetate) | Copper IUD |
|---|---|---|---|
| Active Ingredient | 1.5 mg Levonorgestrel (a progestin) [1.2.1] | 30 mg Ulipristal Acetate (a progesterone blocker) [1.2.3, 1.7.6] | Copper |
| How it Works | Primarily delays or prevents ovulation [1.2.2] | Delays or prevents ovulation, even closer to ovulation than Plan B [1.7.5, 1.2.3] | Prevents fertilization; provides ongoing contraception [1.5.5] |
| Effective Window | Up to 72 hours (3 days) after unprotected sex [1.2.1] | Up to 120 hours (5 days) after unprotected sex [1.7.3] | Up to 120 hours (5 days) after unprotected sex [1.5.5] |
| Prescription Needed? | No, available over-the-counter [1.2.1] | Yes [1.7.3] | No, but requires insertion by a healthcare provider [1.5.5] |
| Interaction with BC Pills | No negative interaction. Continue pills as scheduled [1.5.2]. | Yes. Wait 5 days before resuming hormonal birth control [1.7.4]. | No hormonal interaction. |
Other Medications to Consider
Certain medications and herbal supplements can reduce the effectiveness of levonorgestrel-based emergency contraception. These include the antibiotic Rifampin, some medications used to treat seizures (like Carbamazepine, Phenytoin, Topiramate), barbiturates, and the herbal supplement St. John's wort [1.2.5, 1.4.8]. If you are taking any of these, consult a healthcare provider for the best course of action.
Conclusion
In situations of contraceptive failure, such as missing birth control pills, it is safe to take Plan B or other levonorgestrel-based emergency contraception while continuing your regular pill regimen [1.2.1]. After taking EC, you should resume your pills as scheduled and use a backup barrier method for seven days to ensure protection [1.3.4]. However, this guidance does not apply to the prescription EC pill, ella, which requires a five-day break from hormonal contraception [1.7.4]. Emergency contraception is an important backup but is not as effective as consistent use of primary birth control methods and should not be used as a regular form of contraception [1.2.4].
For more detailed information, you can consult the CDC's guide on Emergency Contraception.
