What does diabetes do to cause foot pain?

Too much sugar. Elevated sugar levels interfere with the very small blood vessels and the nerves in the feet to cause neuropathy. The problem may be pain - or lack of any sensation in the feet.
Several things. Two main problems: peripheral neuropathy(inflammation of the nerves) which the foot to hearts: peripheral vascular disease which make the circulation slow or absents, that also cause pain.
Nerve disfunction. Depending on the affected nerves, symptoms of diabetic neuropathy can range from a numbness and tingling sensation, possibly a burning sensation, to an uncomfortable painful sensation of the extremities. Neuropathy may affect your digestive system, urinary tract, blood vessels and the heart. For some people, the symptoms are mild; for others, it can be painful and disabling.