I wouldn't wear one with my mental health diagnoses on it. I'd be afraid of someone seeing it as I don't tell many people outside my immediate family. All my close friend knows is that I have depression. I told someone my bipolar diagnosis once and it ended badly and with me being unable to return to the university I was studying at.

I do have a card in my wallet with a list of medical conditions (I have other conditions besides the bipolar diagnosis), medications and dosages, medication allergies, preferred hospital, doctor's contact information and who to contact in case of emergency. It was a nice card I filled out and printed for free from an online website. It has come in handy in non-emergency situations like when I go to a new doctor--I'm on so many medications I don't even remember them all.

I would wear one if I had a severe reaction to a certain medication and I probably should because there are some antibiotics I'm allergic to that have put me in the ER or the hospital before.