There are two main forms of diabetes, insulin dependent diabetes (type 1) and non-insulin dependent diabetes (type 2). The causes, short term effects and treatment can be very different, but the long term health problems are very similar and this is why they are grouped together. Both diseases do not effect digestion, but have complications at varying levels with glucose, used for energy.
In type 1 diabetes, the pancreas does not produce insulin, the hormone needed to lower blood sugar levels in the blood stream. In type 2 diabetes, this process does not work efficiently for various reasons. The body produces insulin, but in either low numbers and/or the body does not respond very well to the hormones or signals, this is called insulin resistance.