What cause this much of high sugar in Blood?

The process of changing blood sugar into cells is done with the use of Insulin. Insulin is made in the pancreas, which is an organ near the stomach. But when its start dis-functioning or not work at all or your body stops making enough insulin then the sugar lever stays into the blood itself causing excess sugar level, resulting Diabetes. If not cured properly Diabetes can cause blindness, heart disease, Stroke etc. If pregnant women are suffering from it during pregnancy, it is most likely that born child will be born with Diabetes.