How Ella Works for Emergency Contraception

Ella was approved as emergency contraception by the FDA in August 2010. Ella consists of just one oral pill (ulipristal acetate, 30 mg). Ella can be used by women to prevent an unintended pregnancy after unprotected sex or contraceptive failure with just one pill that can be taken immediately.

Morning-after pill
Jacques LOIC / Getty Images

Ella is most effective if taken right away, but it can be used for up to 120 hours (5 days) after unprotected sex.

Other emergency contraception options, Plan B One-Step, Next Choice One Dose, My Way, Take Action, and Next Choice, are FDA-approved to be used up to 72 hours (three days) after contraceptive failure or unprotected intercourse.


Ella is thought to work for emergency contraception primarily by stopping or delaying the release of an egg from the ovary, so no egg will be available for a sperm to fertilize.

Though Ella prevents ovulation for as long as five days after unprotected sex, there is some concern that women may mistakenly believe that once taking Ella, it can further protect them against pregnancy from any additional acts of unprotected sex for five days. This is not the case, as sperm from additional sex can outlive the initial five-day window.

Ella contains ulipristal, a non-hormonal drug that blocks the effects of key hormones necessary for conception.

Ella belongs to a class of drugs called selective progesterone receptor modulators. The only other approved drug in this class is mifepristone, better known as RU-486. Mifepristone is approved for use as part of a regimen that induces abortion.

Because it is better absorbed by the body than mifepristone, Ella can be used at low doses that prevent conception but that should not cause abortion. It remains unclear, though, whether Ella might increase the rate of spontaneous abortion in the few women who become pregnant despite using the drug.

There is also confusion as to whether or not Ella may cause harm to an existing pregnancy (if the woman is actually pregnant when taking Ella), although there is currently no substantial evidence that it does.

What It Is Not

Emergency contraception is often mistakenly confused with the early abortion pill, RU486 (also referred to as M&M, Mifeprex, mifepristone or medical abortion). These two medications serve two different purposes and work completely differently from one another.

Ella is not an abortion pill. It is not effective if taken after a woman is already pregnant.

According to the FDA, Ella is not for use to end an existing pregnancy.

When to Use

To reduce the risk of an unplanned pregnancy, Ella should be taken as soon as possible within 120 hours (five days) of unprotected sex or contraceptive failure. The sooner Ella is taken, the more effective it'll be.

Ella can also be used any time during your menstrual cycle and can be taken with or without food.

If you vomit within three hours of taking the pill, you should immediately contact your healthcare provider to discuss whether to take another pill.

Who Should Not Use It

Ella is not intended to be used as a substitute for routine contraception use—it does not work as well as most other forms of birth control when they are used consistently and correctly.

Do not take Ella if you know or suspect you are already pregnant. If there is a chance you could already be pregnant, your healthcare provider should provide you with a pregnancy test before prescribing Ella. The risks to a fetus when Ella is administered to a pregnant woman are unknown.

Side Effects

When used as directed, Ella is safe for most women. The most common side effects reported during clinical trials of 2,637 women receiving Ella included:

  • Headache (18%)
  • Nausea (12%)
  • Abdominal and upper abdominal pain (12%)
  • Dysmenorrhea (uterine pain during menstruation) (10%)
  • Fatigue (6%)
  • Dizziness (5%)

After taking Ella, you could likely experience changes in your period. In some cases, your next period may be heavier or lighter, or earlier or later.

It is important to consult a healthcare provider if your scheduled period is more than one week late, as this may indicate that pregnancy could have occurred.

If you are experiencing severe abdominal pain three to five weeks after taking Ella, there could be the possibility that you're having an ectopic pregnancy, so you should seek immediate medical attention.


Ella is most effective the sooner it is started. When taken as directed (within 120 hours of unprotected sex or contraceptive failure), Ella will reduce the chance that you will get pregnant.

Ella is not effective in every case and is only to be used for a single episode of unprotected intercourse. During clinical trials, Ella significantly reduced the pregnancy rate from an expected rate of 5.5% (the number of pregnancies expected without emergency contraception calculated based on the timing of intercourse with regard to each woman’s menstrual cycle) to an observed rate of 2.2%.

Ella appears to be less effective in obese women. During clinical trials, obese women were twice as likely to become pregnant compared with non-obese women.

Ella will not continue to prevent pregnancy during the rest of a woman’s cycle, so make sure that you use a regular birth control method the next time you have sex.

A rapid return to fertility is expected following treatment with Ella for emergency contraception. Therefore, some form of birth control should be used following its use to ensure the prevention of pregnancy

Certain medications and herbal products could also decrease the effectiveness of Ella. These include:

  • Barbiturates
  • Bosentan
  • Carbamazepine
  • Felbamate
  • Griseofulvin
  • Oxcarbazepine
  • Phenytoin
  • Rifampin
  • St. John’s Wort
  • Topiramate


Talk to your healthcare provider if you use hormonal birth control (like the pill, the patch, Depo Provera, NuvaRing).

Using Ella may make your regular hormonal birth control method less effective. If you use Ella as an emergency contraceptive, you should not start your hormonal birth control for at least five days So you should either abstain from vaginal sex during that time or use a reliable barrier method of birth control (such as a condom). You still need reliable contraception if you have sex during any other times in that same menstrual cycle. You should not use Ella more than one time in the same menstrual cycle for different acts of unprotected sex or birth control failure.

Depending on your healthcare provider, you may or may not need an office visit in order to receive an Ella prescription. The manufacturer advises medical providers to confirm or rule out an existing pregnancy before writing a prescription for Ella.

As a precaution, you can ask your healthcare provider about obtaining a prescription for Ella to have ahead of time—just in case an emergency occurs. This way, you will already have a prescription to be filled immediately and will not need to wait to get a medical appointment.


Prices for this morning-after pill vary depending on where you purchase it. Ella may cost at least $55 at the pharmacy. There is an online prescription service that you can use to purchase Ella for $67, plus free shipping and handling for next-day delivery

STI Protection

Ella offers no protection against sexually transmitted infections or HIV.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Ella (ulipristal acetate) label.

  2. U.S. Department of Health & Human Services. Emergency contraception.

  3. Haeger KO, Lamme J, Cleland K. State of emergency contraception in the U.S., 2018. Contraception and reproductive medicine. 3:20. doi:10.1186/s40834-018-0067-8

  4. Bouchard P, Kolanska K, Daraï E, Chabbert-Buffet N, Pintiaux A. Progesterone Receptor Modulators: Current Applications and Perspectives. Encyclopedia of Endocrine Diseases. Elsevier.

  5. Kim A, Bridgeman MB. Ulipristal Acetate (ella): A Selective Progesterone Receptor Modulator For Emergency Contraception. P & T : A peer-reviewed journal for formulary management. 36(6):325-31. 

  6. Emergency contraception. Widely available and effective but disappointing as a public health intervention: a review. Human reproduction. 30(4):751-60. doi:10.1093/humrep/dev019

  7. Planned Parenthood. The Difference Between the Morning-After Pill and the Abortion Pill.

  8. Cleland K, Raymond EG, Westley E, Trussell J. Emergency contraception review: evidence-based recommendations for clinicians. Clinical obstetrics and gynecology. 57(4):741-50. doi:10.1097/GRF.0000000000000056

  9. Afaxys Pharma. Ella brochure (Ulipristal acetate tablet 30 mg).

  10. Kim A, Bridgeman MB. Ulipristal Acetate (ella): A Selective Progesterone Receptor Modulator For Emergency Contraception. P & T : A peer-reviewed journal for formulary management. 36(6):325-31.

  11. Robinson JA, Burke AE. Obesity and hormonal contraceptive efficacy. Women's health. 9(5):453-66. doi:10.2217/whe.13.41

  12. Ulipristal acetate for emergency contraception. Australian prescriber. 39(6):228-229. doi:10.18773/austprescr.2016.082

  13. Planned Parenthood. What’s the Ella morning-after pill?.

By Dawn Stacey, PhD, LMHC
Dawn Stacey, PhD, LMHC, is a published author, college professor, and mental health consultant with over 15 years of counseling experience.