How Effective Is The Morning After Pill?

The Most Effective Morning After Pill*
BUY ellaOne® NOW
Ask Ella
Ask Ella

How effective is the morning after pill? If your regular contraceptive method fails and you find yourself seeking emergency contraception, the wait between taking it and your next period can be a little nerve-racking.

A single instance of contraceptive failure can be life-changing, and it’s always good to know your options if you are trying to avoid a positive pregnancy test. Emergency contraception can be very effective, but you might have some questions about the effectiveness of the morning after pill before you use it.

#AskElla is here to put your mind at ease by answering the big questions about the effectiveness of the morning after pill.

How effective is the morning after pill?

ellaOne® is a type of emergency contraception. There are two ingredients that are used in emergency hormonal contraception (morning after pill) – either ulipristal acetate or levonorgestrel.

ellaOne® contains ulipristal acetate and is the most effective morning after pill* at preventing pregnancy.* Ulipristal acetate is recommended by the Faculty of Reproductive and Sexual Health as the most effective ingredient for emergency contraception. 

 In a clinical trial* it has been shown to be 2.5 times more effective than levonorgestrel when taken within 24 hours of unprotected sex. No contraception is 100% effective, but of 100 women who take ellaOne®, it is approximated that only 2 will become pregnant.

*verify at:

It’s important to note that emergency hormonal contraception is not 100% effective, and will not work once ovulation has already occurred, so it can help to have an idea of where you are in your menstrual cycle. “This method of emergency contraception works by delaying ovulation, so if an egg has already been released close to the time of unprotected sex, then you could still get pregnant,” explains Deborah Evans**, pharmacist and sexual health expert. 

Different forms of emergency contraception carry different levels of effectiveness when taken more than 2 days following unprotected sex. ellaOne® can be taken within up to 120 hours (5 days), but is most effective within 24 hours of having unprotected sex.

Deborah’s advice, should you require emergency contraception, is to seek and take it as soon after unprotected sex as possible. Why? Because the morning after pill is more effective at preventing pregnancy the earlier you take it. 

It’s important to remember that all morning after pills are forms of emergency contraception, and are not forms of regular contraception.

How effective is the morning after pill?
GIF animation of a clip from a movie showing a woman with nausea.

What can impact the effectiveness of the morning after pill?

Throwing Up

The morning after pill is generally well tolerated, however, some women have been known to experience mild side effects, including nausea.

“A small number of women may be sick after taking the morning after pill,” explains Deborah. “If this happens within three hours of taking it, then you may need to take another pill as it may be that not enough of the pill has been absorbed to work.”

Other Medications

Some medications can impact the effectiveness of the morning after pill so it’s vitally important that you give the details of any you’re taking during the consultation process, whether in person with a pharmacist, while filling out a consultation card or when ordering online via ellaOne direct.

“If you have any concerns about your choices and what you should do,” says Deborah, “then your pharmacist or other healthcare professional can advise you on which option of emergency contraception will be best for you.”


You may have heard that the emergency contraceptive pill may be less effective if you have a higher body mass index (BMI) and you may have encountered one of the many sources online suggesting that at a higher BMI it may be best to double your dose, but there is a lot of debate over these findings.⁴ 

ellaOne® is recommended for all women regardless of their BMI⁵ and we would not, under any circumstances, recommend doubling your dose of ellaOne®. If you are unsure you should speak to your pharmacist, or a healthcare professional, such as a GP, or visit a sexual health clinic for more information.  Always read the label and take the medication as instructed.

Unprotected Sex

After having unprotected sex or a contraceptive failure, ellaOne® can prevent pregnancy by delaying ovulation. One question that gets asked a lot is “how long is the morning after pill effective for?”. It is important to understand that ellaOne®’s preventative action applies only to the specific incident of unprotected sex prior to it being taken.

The morning after pill is not effective at preventing pregnancy in any subsequent instances of unprotected sex. Unless you are trying to get pregnant you should not have unprotected sex again after taking the morning after pill. You should always use some form of regular contraception, such as condoms, progestogen-only pills like Hana, or the combined pill, to continue to protect yourself and prevent pregnancy.