It depend how bad it is... Ulcerative Colitis is a horrible condition and it can effect people differently. Is the person attending hospital, maybe in and out of hospital every few months, taking a lot of medication and having monthly infusions to keep the illness at bay. Some people get UC and it can clear up in no time and others get it and suffer the most horrible effects of it, like ulsers in the mouth were you are barely able to talk. I suppose it depends on the how bad the persons condition is. If the GP says your not fit then I would suppose your not fit.