8. Gangrenous Foot

High blood sugar levels can cause damage to the nerves in the feet, making a person unaware of injuries he or she has sustained because of their decreased ability to feel pain. Because they are unaware of their wound, the injury is left untreated, which then leads to infection. In addition to this, diabetes damages the blood vessels that supply oxygen and nutrients needed for wound protection and healing. Because of this, wounds sustained by diabetics tend to heal slower and fester longer, causing gangrene. When this happens, the need to surgically remove the affected part is called for, and it is not unheard of that patients lose their leg entirely.