Insulin is secreted by the gland called pancreas . The main purpose of insulin is to maintain the glucose levels in human body. Pancreas is located below stomach and mostly yellow in colour . When the level of sugar level increases in the body , generally it ranges between 100-120 , if it is exceeded upto this the person is called as diabetic patients and the problem is diabetes.
Increase in level of glucose will directly effect to the vital organs like kidney failure. In most of the cases person may faint due to this.
Insulin is a hormone which is usually naturally produced in the body and maintain the glucose level when this natural process get disturbed the person is adviced to take insulin .
Also they are advised to not eat the products containing glucose like potatoes etc . Diabetes is common disease , it may be happen to any person genetically also but can cause severe problems like cardiac arrest and kidney failure.
Hope you will be satisfied with my answer.