Neuropathies are characterized by an increasing loss of nerve fibre function – a diabetic neuropathy suggests that it is caused by complications from high blood sugar levels in Type 1 and Type 2 diabetes mellitus. Neuropathies affect up to 50% of diabetics making it the most common complication. Diabetic peripheral neuropathies start at the ends of the furthest part of the longest nerves and as the disease progresses, the symptoms move toward the spine. This results in the characteristic “glove and stocking” syndrome wherein the numbness and tingling affect the whole foot and hand in a glove and stocking pattern.
The reason the increased blood sugar levels or hyperglycemia causes the breakdown of the nervous tissue is not well understood although there are several theories and it is generally agreed that multiple factors may play a role.
From: http://emedicine.medscape.com/article/1170337-overview