The manufacturers don't recommend it
You are absolutely right, the sooner you take the e-pill (also called morning-after pill, emergency contraception, or P2) after having unprotected sex, the better. So it makes sense to ask if you can take it before having sex.
The manufacturers of emergency contraception advise to take the pills after sex – and that's what you should stick to for the best results.
The e-pill would most likely protect you if you took it right before having sex. But, as this has not been thoroughly researched, you are better off following the manufacturer's instructions.
The e-pill might protect you from unintended pregnancies if you have sex again after taking a pill. Again, no research has been done to see how long the preventative effects last – so you are putting yourself at risk of getting pregnant. Ideally, you should take an e-pill every time you have unprotected sex. Keep in mind though that's not ideal at all.
For emergencies only
There is nothing wrong with keeping an e-pill at home, so you don't have to rush to the chemist in case of an emergency. But please don't rely on it all the time.
The e-pill is called emergency contraception for a reason: it should only be used in case of emergency. For example, if your regular birth control method fails.
The high levels of hormones in the e-pill could mess with your cycle and cause unpleasant side effects like nausea or delayed periods.
So, if you are having sex regularly, I would strongly advise choosing a more reliable birth control method, such as the pill or an IUD. Condoms are also a great option, especially if you also need to protect yourself from STIs.
Talk to your healthcare professional to get information on what the best options are for you.
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