Plan B® versus Ella®: How Are They Different and Which Emergency Contraception Is Better?

Sexual Health

Plan B® versus Ella®: How Are They Different and Which Emergency Contraception Is Better?

Editorial Team

So what exactly is Plan B®? Is it a type of emergency contraception or a brand name? Why does every morning-after pill get referred to as “plan B” so often? What is the difference between Plan B® and Ella®, and which one is better at preventing unwanted pregnancy?  

All of these are valid questions and we hope to clear some of the confusion up.

In this article, we will be discussing the major differences between Plan B® and Ella® and why we at Zoey prefer Ella® as our choice of emergency contraception. 

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Differences Between Plan B® and Ella®

Here are the 3 main differences between Plan B® and Ella®

1. Main Active Ingredient

The most significant difference between Plan B® and Ella® is the main active ingredient present in the emergency contraception pill. 

The main active ingredient in Plan B® is levonorgestrel, a synthetic form of progesterone. As a synthetic hormone, levonorgestrel is able to mimic progesterone which tricks the body into thinking that it is pregnant. This stops the ovaries from releasing an egg and prevents ovulation from happening. 

The main active ingredient in Ella® is ulipristal acetate, a form of Selective Progesterone Receptor Modulator (SPRM). While ulipristal acetate achieves the same goal as levonorgestrel, which is to prevent or delay ovulation from occuring, it takes a different route to the same destination. Instead of mimicking progesterone, ulipristal acetate suppresses progesterone instead which can delay ovulation for up to 5 days - this gives the sperm plenty of time to die off before the egg is released. 

Depending on what stage you are at in your menstrual cycle, Ella® can also thin your uterine slightly which can further decrease the likelihood of pregnancy as it makes it harder for the fertilized egg to implant itself. 

2. Effectiveness And Time Frames

Another difference between Plan B® and Ella® is its effectiveness rates and the time frame you would have to take the emergency contraceptive before its effectiveness begins to diminish.

If you choose to take Plan B® (or any other levonorgestrel-based emergency contraception pill), it is recommended that you take the pill within 72 hours (or 3 days) of having  unprotected sex. In a study carried out by Princeton University, it was found that Plan B® had an effectiveness rate of 95% when taken within 24 hours of having unprotected sex, and an average effectiveness rate of 88% within 72 hours. 

Ella, on the other hand, beats Plan B® in terms of its effectiveness rates and has a longer time frame that retains its high effectiveness rates. In a study carried out by the World Health Organisation, Ella (and other ulipristal acetate-based emergency contraception pills) were found to have an effectiveness rate of 98.8% when within 24 hours of having unprotected sex, and can be still be as effective when taken between 72 to 120 hours (or 5 days) after having unprotected sex. 

It is still recommended that all emergency contraceptive pills be taken as soon as possible, to ensure that unwanted pregnancy does not occur.  

3. BMI Restrictions 

Another important difference between Plan B® and Ella® is the possible limitation of its effectiveness when it comes to treating women with higher BMIs (Body Mass Index).

According to Princeton University, there was evidence to suggest that Plan B® (or other levonorgestrel-based emergency contraception pills) were less effective for women with a BMI of 26 and above. 

Ella® on the other hand still retained its effectiveness rates for women with BMIs up to 35.  

Why Zoey Chooses Ella As Its Primary Emergency Contraception 

While emergency contraception or morning after pills can often be referred to as “plan B pills”, the sale of the branded medication Plan B® or Plan B One-Step® is not available in Singapore as an over-the-counter medication. 

If you require emergency contraception pills in Singapore, you will need to consult a doctor and get a prescription. Commonly prescribed emergency contraception pills in Singapore are usually Postinor®-2 (a levonorgestrel-based emergency contraception pill similar to Plan B One Step®) and Ella®.

At Zoey, we chose Ella® to be our primary emergency contraception pill due to its high effectiveness rate, longer time frame to take the pill and that it can be effective for women with BMIs from 25 to 35. 

If you’ve recently had unprotected sex and require emergency contraceptive pills, you can consult one of our doctors. Here at Zoey, we understand that emergency contraception is a time-sensitive prescription and will endeavor to get your prescription delivered to you within the 4-hour delivery promise.  


“Emergency Contraception.” World Health Organization, World Health Organization, (Link) 2021. Emergency contraception: Effectiveness of emergency contraceptives. [online] Available at: <*> (Link) 2021. Emergency Contraception: ella or progestin-only?. [online] Available at: <> (Link