For PrEP to protect you, it needs to be taken before you come in contact with the virus. This means that you should test negative for HIV before starting PrEP.
If you’re unsure of your status, it’s still a good idea to get tested before starting PrEP. That way, you can be sure that PrEP is right for you and start taking it as soon as possible if it is.
Most online PrEP providers will require you to take an HIV test before they prescribe PrEP to you.