ADD coupled with other diseases

Hello, I'm new here and first off I have to say I love it! I already feel the support I have been needing.

I've been wondering if anyone has advice on how to handle a partner with ADD and another disease on top of it. My fiance has ADD as well as diabetes. I've tried the concerned approach and i've also tried the motherly "you need" approach in trying to get him to take care of himself. As of right now he has been off his insulin and such for about 2-3 months. I've repeated myself until I'm blue in the face and have even tried making him an appointment myself. Nothing seems to work. I always get "it'll be fine" or "i forgot" responses. I've even had a couple nurses explain to him the consequences of not taking his medication. Basically, I've tried everything short of pinning a note to his shirt and shoving him in the door. Does anyone have any advice or experience in handling situations such as this?