Diabetic neuropathy is a common complication of diabetes, in which nerves are damaged as a result of hyperglycemia (high blood sugar levels).

People with diabetes commonly develop temporary or permanent damage to nerve tissue. Nerve injuries are caused by decreased blood flow and high blood-sugar levels, and are more likely to develop if blood-sugar levels are not controlled well.

Some people with diabetes will not develop nerve damage, while others may develop this condition relatively early. On average, the beginning of symptoms occurs 10 to 20 years after diabetes has been diagnosed. Approximately 50% of people with diabetes will eventually develop nerve damage.

Peripheral nerve injuries may affect cranial nerves or nerves from the spinal column and their branches. This type of neuropathy (nerve injury) tends to develop in stages. Early on, intermittent pain and tingling is noted in the extremities, particularly the feet. In later stages, the pain is more intense and constant. Finally, a painless neuropathy develops when pain sensation is lost to an area. This greatly increases the risk of severe tissue injury because pain no longer alerts the person to injury.

Autonomic neuropathies affect the nerves that regulate vital functions, including the heart muscle and smooth muscles. Low blood pressure, diarrhea, constipation, sexual impotence, and other symptoms can be caused by autonomic neuropathies.

• Numbness (decreased or lost sensation to a body part)
• Tingling
• Diarrhea
• Constipation
• Loss of bladder control
• Impotence
• Facial drooping
• Drooping eyelid
• Drooping mouth
• Vision changes
• Dizziness
• Weakness
• Swallowing difficulty
• Speech impairment
• Muscle cramps

Note: Symptoms vary depending on the nerve(s) affected and may include symptoms other than those listed. Symptoms usually develop gradually over years.

Physical examination, including neurological and sensory tests, may reveal many neuropathies. A common early finding is the absence of ankle reflexes.Health care providers often test for loss of sensation in the feet with a brush-like instrument called a monofilament.