In the absence of screening and treatment of diabetes, the main risk is that the disease is revealed by a complication.It is more often a complication of vascular order (coronary insufficiency, myocardial infarction, stroke, arthritis of the lower limbs).
It could also reach the small vessels, the retina with a decline in visual acuity, renal damage with emergence of albumin in the urine, and then renal insufficiency (diabetes becomes the first cause of end stage renal disease).
It may occur a nerve damage (neuropathy), of an accident such as a facial paralysis. In addition, in the case of a neuropathy with disorder of peripheral nerves, appear signs of glue polyneuritis over and a burning sensation under the feet or the impression of walking in the cotton.
Eventually, acute complications are favored by a diabetes unbalanced and therefore undiagnosed. It can be for example an infection from a wound which heal properly.
Diabetes is an insidious disease, the objective is therefore an early diagnosis to avoid the risk of complications, or even a diagnosis to the stage of pre-diabetes can to treat by hygieno-dietatry measures even before the diabetes appears.
See also Diabetes symptoms, how to detect them early 
