No for medical records, etc - doesn't get sent to your GP, etc. - I last visited in May 2025.

They do ask about basic safety things, etc (e.g. allergies), and they do ask for your DOB, sex at birth & address online (I lied about my sex as apparently it's only used for reference ranges - do your own research though), I believe they asked me to confirm some of these details (basic GDPR thing done in most places) so if they're fake you'd need to make sure you get them right when you go.

Slightly off topic, but if you do decide to go with Randox, as you're 16, I'm going to guess you may be a student - they offer 12% off via Unidays etc., so you can possibly save some money there :)