I got told to undress to my underwear at CAMHS?

I had my CAMHS ( Child and Adolescent Mental Health Service) appointment today, I went for self harm, an eating disorder and suicidal thoughts/attempts but I got taken in to a room to which I was told to strip to my underwear to be weighed... Are they allowed to do this? Should I have been informed previously? I said I didn't want to but they didn't give me a choice, was this fair? I didn't expect this and it made me feel violated and very uncomfortable. The nurse was lovely but I didn't feel comfortable having to bare all for a weigh in (which is one of my fears).