When blood glucose rises it will eventually spill over into the urine and draw water out of the body. This causes an increase in urinary frequency. The body becomes dehydrated and the patient complains of being thirsty. The higher blood glucose than normal may seep into various structures of the body such as the lens of the eye and cause visual blurring.
Glucose will not be getting to the tissues for energy production because without normal insulin action it will be getting stuck in the blood circulation. The tissues will in effect become starved of fuel and they will complain, the patient starts to feel tired and lethargic. Exercise will become noticeably more difficult. Breathing being controlled by chest muscles will be less effective and patients will notice being more puffed and breathless.
Some patients may notice all of the above over a relatively short period of time. This may mean rapid destruction of the insulin producing cells of the pancreas as often occurs in Type 1 diabetes. The sudden loss of insulin can cause unexplained and rapid weight loss.
Other patients may not notice any symptoms at all. If accompanied by only mild rises in blood glucose as often happens in Type 2 diabetes the lack of symptoms often delay the diagnosis. This should not be thought of as mild diabetes because the long delay in treatment provides ample time for the abnormalities within the circulation to cause the well- documented long-term complications. In fact many people who present with Type 2 diabetes already have signs of diabetic eye disease, kidney disease, foot ulcers and coronary heart disease.