Is it ok for gym personal trainers to be giving out medical advice and dietitian advice?

it depends how realiable they are. they can know a lot about the body and functions for health but about dietitian advice, i'd say the only advice you should take is what to eat before and after workouts to keep up energy and what workouts to do. don't listen to them giving out perscriptions for weight loss they can't do that. and somethings they say might make you fatter or something so you come to them more (that's unlikely though, just thinking outside the box)