How Long Can You Wait to Take Plan B Emergency Contraception?
Plan B (levonorgestrel) is an emergency contraceptive pill that works by temporarily halting ovulation. Plan B is sometimes referred to as the morning-after pill. Plan B is meant to be taken within 72 hours (or 3 days) of having unprotected penis-in-vagina sex. However, it’s best to take Plan B as soon as possible for optimum effectiveness.
Timing and Effectiveness
The sooner you take Plan B, the better your chances are of avoiding pregnancy. In fact, one manufacturer of the medication recommends taking it within 12 hours, if possible. They also state that Plan B is 95 percent effective when used within 24 hours. Plan B is approved by the Food and Drug Administration (FDA) for use within 72 hours (or 3 days) of having unprotected sex. Although it works up to five days after unprotected sex, the sooner you take it, the better it'll work.
How It Works
The only active ingredient in Plan B is levonorgestrel. Levonorgestrel is a synthetic-steroid progestin hormone that mimics progesterone. Progesterone is a naturally occurring hormone that’s produced by your body after ovulation has taken place. When progesterone levels are high, ovulation cannot occur. Taking Plan B tricks your body into thinking you’ve already ovulated. This temporarily stops your ovary from releasing an egg.
Important considerations:
- Plan B can’t stop or reverse ovulation that has already occurred.
- It also can’t stop an established pregnancy from progressing.
- Sperm can live for up to 5 days within the female reproductive tract.
Comparison of Emergency Contraception Options
There are different types of emergency contraception available depending on how much time has passed and your specific needs.
| Method | Effectiveness Window | Availability |
|---|---|---|
| Plan B One-Step | Up to 3-5 days (Best within 72 hours) | Non-prescription / Walk-in |
| ella (ulipristal) | Up to 5 days (120 hours) | Prescription only |
| ParaGard (Copper IUD) | Within 5 days | Medical professional insertion |
Potential Side Effects
Plan B is considered safe to take. It may, however, generate some mild side effects, such as:
- tender breasts
- tiredness
- mild cramping or abdominal pain
- dizziness
- headaches
- nausea and vomiting
- periods that are lighter or heavier
- periods that come early or late
As indicated above, Plan B may temporarily alter your menstrual cycle and flow. Some people find their periods are delayed. Others notice they menstruate earlier than expected. These changes are temporary and will not impact your fertility.
Why Plan B Might Not Work
There are a few reasons Plan B may not work for you. Research from 2017 suggested that Plan B may be less effective in people who weigh over 155 lbs. or have a body mass index (BMI) >30. Furthermore, vomiting is an occasional side effect of Plan B. If you vomit within 2 hours of taking it, your system might not have had an opportunity to absorb the medication completely. If this occurs, call your doctor. You may need another dose of Plan B.
Other Emergency Contraceptive Options
If more than 3 days have passed since you had unprotected sex, Plan B should not be your first-line emergency contraception choice. There are other emergency contraceptives that may be more effective if too much time has passed:
ella: ella (ulipristal) is another type of emergency contraception pill. It works up to 5 days after having unprotected sex. ella is only available by prescription and should not be taken in conjunction with Plan B. Ella blocks the hormones your body needs to conceive.
Intrauterine Device (IUD): The IUD is the most effective emergency contraception there is. The ParaGard copper intrauterine device (IUD) can be used as emergency contraception within 5 days of having unprotected sex. The copper in the IUD reduces sperm mobility, making it almost impossible for a sperm to fertilize an egg. It can lower your chance of pregnancy by 99.9%.
Key Differences Between Pills
It is important to note that Plan B is better when breastfeeding. Ella can be used if you discard your breast milk for 24 hours after taking it, but Plan B and its generics are safe for baby. Additionally, if you use hormonal birth control, do not take it for 5 days after taking Ella, as the two medications may counteract each other.