The causes of diabetic neuropathy are not completely understood but appear to largely involve damage to nerves from high levels of blood sugar, according to the Mayo Clinic. The nerves located in the legs are also especially vulnerable to the loss of circulation that often accompanies diabetes.
High blood sugar can damage nerves directly and also weakens the blood vessels that surround them, explains the Mayo Clinic. This reduces the oxygen supply to the nerve and leads to damage from oxygen starvation over time. Diabetes also causes hardening of the arteries, according to the American Diabetes Association, leading to even more restricted oxygen supplies to peripheral nerves and further neuropathy.