pathophysiology of diabetes:

Insulin is a hormone secreted by the beta cells in the Islets of Langerhans of the pancreas. Insulin is a protein unlike other hormones. Glucose is a simple sugar found in food.

Glucose is an essential nutrient that provides energy for the proper functioning of the body cells.  

When there is an increase in the level of blood sugar, insulin is released by the pancreas into the blood.

Insulin helps in the absorption of glucose from the blood, storing it as glycogen in the liver and muscle and it stops the body from using fats as a source of energy.

In the absence of insulin, glucose from the blood is not absorbed by the body cells, thus the body begins to use fats as an energy source. This is when the disease condition, that is Diabetes Mellitus occurs.

In the case of Type I Diabetes, no insulin is produced by the pancreas of the body where as in the case of Type 2 Diabetes, enough or sufficient insulin is not secreted by the body, resulting in the non-absorption of glucose by the body cells resulting in the presence of glucose in the blood and urine.