Once you take it, ellaOne® works by delaying ovulation. ellaOne® is most effective the sooner you take it, as reduces the chances that you will ovulate in the time between having unprotected sex and taking emergency contraception.
Generally, ellaOne® is well tolerated but, like any medicine, some people experience side effects after taking ellaOne®. For more information about potential side effects, please see here.
It is important to remember that ellaOne® is only effective for a specific instance of unprotected sex. Taking ellaOne® will not protect you for future occasions of unprotected sex. Your fertility will return to normal very quickly, and you should use a condom until your next period arrives, even if you are using a hormonal method of contraception like the pill.