Well, if you have Type 1 diabetes in the family, you'll know it when you see it! It usually seems to appear suddenly with a vengeance, and the person will be VERY sick. If left untreated, the person will fall into a coma and eventually die. You can't miss that! There are some tests that can screen for the auto antibodies that are the precursor to Type 1, but since we have no way to prevent it, all these really do is say that you are "high risk" for becoming T1. You may or may not get it. Either way, the symptoms of T1 are VERY obvious, in practically all cases.

For a family with Type 2, regular screening is a must, in my opinion. It doesn't always have symptoms early on.