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Emergency Contraception – “Morning After Pill”

Emergency contraception provides an important safety net when you have sexual intercourse and no contraception is used or the contraception used is compromised (missed birth control pills, missed Depo injection, condom slips/breaks, etc.).

Emergency contraception pills are hormone-containing pills taken to give you a burst of hormonal contraception, which will likely prevent ovulation, fertilization, and/or implantation. Emergency contraception will not harm an already existing pregnancy.

You should take the emergency contraception pill as soon as possible; up to 120 hours (5 days) after unprotected sex.

Emergency contraception pills are free to all Yale students and Yale Health members when acquired at the Yale Health Center.

Emergency Contraception Pills

  • My Way (Plan B – levonorgestrel) is available over-the-counter, without a prescription.
  • Ella (ulipristal) is available by prescription from a provider in Student Health, OB/GYN or Acute Care.

(See Emergency Contraception Comparison Chart and/or contact the Yale Health Ob/Gyn Department if you’re not sure which option is best for you.)

Where to Get Emergency Contraception at the Yale Health Center

(free for all Yale students, and all Yale Health members)

  • Yale Health Pharmacy (either going to the Pharmacy directly, or after consulting with a provider in one of our clinical departments)
  • Acute Care

Other Locations (purchase price varies)

  • Commercial pharmacies, like CVS, Walgreens, etc.


Emergency contraception pills reduce the risk of pregnancy by approximately 75%. In other words, out of 100 women who have unprotected intercourse mid-cycle, approximately 8 would become pregnant. With use of emergency contraception pills, only 2 of the 100 would become pregnant. 

  • My Way becomes less effective if used 3-5 days after unprotected sex, while Ella’s effectiveness stays the same for the full 5 days.
  • Both medications are less effective for obese women. My Way retains its effectiveness up to a BMI of 30. Ella is effective up to a BMI of 35.
  • My Way is less effective when unprotected sex occurs closer to the time of ovulation. Ella is more effective than My Way closer to ovulation.

Side Effects of Emergency Contraception Pills

The most common side effect is nausea, with or without vomiting. There are ways to decrease this if you become nauseous easily. Take the pill with food. You may elect to take prescription or over-the-counter anti-nausea medications about 30 minutes prior to the first dose of an emergency contraception pill. 


In 1997, the Food and Drug Administration reviewed the evidence and concluded that emergency contraception pills are safe and effective. In 2006, the FDA approved the sale of Plan B/My Way over the counter (OTC).

If you happen to already be pregnant and take emergency contraception, the hormones in emergency contraception pills have been shown not to affect the baby.

Important Note: Emergency contraception should not be used as your primary method of birth control. It is much less effective than methods designed for continuous protection from pregnancy. If you pick up 4 or more emergency contraception pill doses in a year, the Yale Health Pharmacy will notify the Ob/Gyn Department, so they can reach out to discuss better options for preventing pregnancy.

Taking the Medication

A Yale Health nurse or pharmacist will give you a dose of My Way, or you may have a provider prescribe Ella for you.

The treatment consists of one pill. If your provider recommends an antinausea medication, take it first. Wait 30 minutes to one hour and then take the emergency contraception pill. It is helpful to take the pill with food, and not on an empty stomach.

Your period may start a few days earlier or a few days later than expected. If it does not start within a week of when expected, you should come in for a pregnancy test and/or evaluation.

If you have not started your period within 3 weeks from the date of using emergency contraception, you should come in for a pregnancy test and/or evaluation. If you feel pregnant sooner, you should do a pregnancy test at that time.

Reasons Not to Take Emergency Contraception

Emergency contraception pills might not be a good option for you if you have a history of allergy to the medication, if you are significantly overweight, or if the unprotected sex occurred more than 120 hours earlier. There are no known medical conditions for which emergency contraception is unsafe.

Remember, even if it’s been more than 120 hours, and the episode occurred at mid-cycle, the chances of becoming pregnant are still low (less than 10%).

Additional Option

The Paragard copper-containing IUD, if inserted within 5 days (120 hours), provides over 99% effective emergency contraception, plus ongoing effective contraception for up to 10-12 years. It is inserted with a minor office procedure in the Ob/Gyn Department. You can make an appointment via MyChart or by calling 203-432-0222.

Additional Concerns

If barrier contraception (condom) wasn’t used, or if it failed, you should consider the chance that you’ve been exposed to a sexually-transmitted infection (STI). You should discuss this further with a nurse or provider.

If the sex was unprotected because it was nonconsensual (for example, sexual assault or date rape), please talk to one of our caregivers to learn about the resources available to you at Yale, including The Share Center.