Scientists have found that when tissues have a high level of glucose, sorbitol builds up and apparently damages the membranes lining body tissues. Studies have shown that proteins age more quickly when exposed to high glucose. This has the effect of weakening certain connective proteins called collagens, which line and support nerve tissue. While these changes occur with normal aging, high blood glucose speeds up the damage. The symptoms of diabetic neuropathy vary a great deal.
Some people notice no symptoms, while others are disabled by severe problems.
Neuropathy may cause both pain and insensitivity to pain the same person. Often, symptoms are slight at first, and since most nerve damage occurs over years, mild cases may go unnoticed for a long time. In some people, though, mainly those afflicted by mononeuropathy, the onset of pain may be sudden and severe. A doctor diagnoses neuropathy from symptoms and a physical exam. During the exam, the doctor may check muscle strength, reflexes, and sensitivity to position, vibration, temperature, and light touch.