I'd have a chat to them. You might be able to do the theory but not the prac. It can be very physically taxing. There's no reason why you can't start it although it will depend on the Unit/Division as some may prefer to put someone on who can complete and start straight away - especially if they are short on members. Where abouts are you thinking of doing it?

Some people consider it to be a full on course and struggle to keep up with the study demands. My Step Mum is a Registered Nurse and struggled to keep up with the course requirements.

HTH

MG