The first thing which I would recommend a person who has a type 1 diabetic friend is to use empathy. This means, putting yourself in the other person’s shoes. If you do this, everything else will follow.
The most supportive friends I have just happen to be really good at this. When my blood sugar is low they know to be patient while I begin to feel better. They don’t crack jokes about the diabetes and they openly admire the way I deal with things. They also listen carefully when I talk about the diabetes-as they know it is a very sensitive subject and they don’t try to give me advice about things they don’t know about.
Another great thing you can do if you have a friend with type 1 diabetes is encourage them to do whatever they need to do to take care of themselves. Don’t wince when they have to give an insulin shot. Do you think looking at them give a shot hurts more than being the one suffering from the disease? I have a family member who always made a big scene when I gave a shot. He acted as if he was being tortured. I finally got mad one day and said, “Believe me, this hurts me more than you.” He finally stopped being so inconsiderate and thought about things from MY perspective.
Finally, if you see that your friend is trying not to eat chocolate cake, do not say, “come on, just have a little!” This is not what a real friend does. A real friend, when seeing their diabetic friend take a bite of chocolate cake which they just tried to resist might smile and remind their friend to take care of themselves.