Confirming user identity on registration

Hi all.

Not sure this is going to be easily done or even possible without some other service but thought I’d ask anyway.

Basically a have a doctors site set up and i would like for patients to be able to request a copy of medical records online, now obviously this needs to be secure and i need to verify there ID when they register.

Is this something that can be easily done, or would i be best looking for a 3rd party solution?

I already have a registration form set up and to confirm email etc.

Thanks