How does diabetes kill someone?

There are many ways. Diabetes affects your nerve and immune system drastically, causes tissue damage and it has other severe effects on your body that shorten your life expectancy. But the main one is without a doubt the fact that 85% of Type II diabetics are overweight. Being overweight directly causes many fatal diseases and causes a lot of life time expectancy reducing factors. The average type II diabetic's life expectancy is reduced by 10 years, and type I diabetics have it reduced by 20 years.