Major complications of include stroke, blindness, and ulcers.

Diabetes
Diabetes affects many organs in the body and causes complications that can be serious and irreversible. When blood sugar is not tightly controlled, the organs can suffer severe damage. By carefully controlling their blood sugar (glucose), however, people with diabetes can reduce their risk of complications. Poorly controlled blood sugar can cause long-term problems by damaging eyesight, the heart, the arteries, the kidneys, and nerve endings. The consequences of poor blood sugar control over time include blindness, foot ulcers or amputation, heart attack, stroke, angina, hypertension, kidney failure requiring dialysis, neuropathies (which can lead to loss of feeling in the arms and legs), and impotence.