Although there are two types of complications of diabetes: acute and chronic, by diabetic complications, here we mean chronic (long term) complications only. [Acute or short term complication is hypoglycemia (low blood sugar) due to excess dose of insulin, oral medications, exercise or combination of these.]
The chronic or long term complications arise due to damage to the blood vessels caused by high blood sugar levels (hyperglycemia) for long periods of time (several years). The complications are damages to the following organs:
Diabetes accelerates atherosclerosis (hardening of arteries) of larger blood vessels which over a period of time leads to heart disease, stoke and claudication (pain in legs due to inadequate blood supply). Similar damage occurs to the tiny blood vessels called capillaries leading to the damage of eyes (retinopathy), kidneys (nephropathy) and nerves (neuropathy).
http://adam.about.com/care/diabetes2/diabetes2_step10.html
As we saw above that Diabetes accelerates atherosclerosis and subsequently results in heart disease. There are other cofactors like hypertension, high blood cholesterol, smoking, lack of exercise etc. which add to the risk of developing heart disease. For further information on heart disease, go to Heart Disease
The damage caused to the kidneys due to diabetes is called diabetic nephropathy. For further information on kidney damage, go to Diabetic Nephropathy
diabetic-nephropathy-topic-overview
The damage caused to the eyes due to diabetes is called diabetic nephropathy. For further information on eye damage, go to:
Our Diabetic Retinopathy page
http://www.mayoclinic.com/health/
http://www.allaboutvision.com/conditions/diabetic.htm
http://medweb.bham.ac.uk/easdec/Information_for_patients.html
The damage caused to the nerves due to diabetes is called diabetic neuropathy. For further information on eye damage, go to:
preventingcomplications/a/neuropathy.htm