The only two vibrant forums I know of are this one and the Squidoo forum. That's not to say that there aren't others, since I'm sure there are. The thing is, these days more and more forums seem to be declining in active membership. I think this is largely do to the rise of social media. People seem to prefer to have their online discussions on sites like Twitter and Facebook as opposed to forums.
You can come to www.dermatalk.com It`s really nice forum. Thanks! - SeoHawk P.S. I`m not admin there...
http://www.diabetesforum.com/ http://www.diabetesforums.com/ http://www.diabetesdaily.com/forum/ http://www.dlife.com/diabetes-forum/ I have researched it in Google.. I just hope that it helps.. But I am not really sure if it has many members.. Just checked it..