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

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 well controlled.

Some people with diabetes will not develop nerve damage, while others may develop this condition early. On average, symptoms begin 10 to 20 years after the diabetes diagnosis. Approximately 50% of people with diabetes will eventually develop nerve damage.

Peripheral nerve injuries may affect nerves in the skull (cranial nerves) or nerves from the spinal column and their branches. This type of nerve injury (neuropathy) tends to develop in stages.

Autonomic neuropathies affect the nerves that regulate vital functions, including the heart muscle and smooth muscles.

Digestive tract:

• Constipation
• Diarrhea
• Nausea and vomiting
• Swallowing difficulty

Legs and arms:

• Deep pain, most commonly in the feet and legs
• Loss of the sense of warm or cold
• Muscle cramps
• Numbness (if the nerves are severely damaged, you may be unaware that a blister or minor wound has become infected)
• Tingling or burning sensation in the extremities, particularly the feet
• Weakness

Other symptoms:

• Dizziness
• Drooping eyelid
• Drooping face
• Drooping mouth
• Impotence
• Light-headedness when standing up (orthostatic hypotension)
• Loss of bladder control
• Rapid heart rate
• Speech impairment
• Vision changes

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 nervous system (neurological) and sensory tests, may diagnose 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.

Electrodiagnostic testing may be done.

The goals of treating diabetic neuropathy are to prevent the disease from getting worse and to reduce the symptoms of the disease.

Tight control of blood sugar (glucose) is important to prevent symptoms and problems from getting worse.

Medications may be used to reduce the symptoms in the feet, legs, and arms. These medications include:

• Antidepressant drugs, such as amitriptyline (Elavil), doxepin (Sinequan), or duloxetine (Cymbalta)
• Anti-seizure medications, such as gabapentin (Neurontin), pregabalin (Lyrica), carbamazepine (Tegretol), and valproate (Depakote)
• Drugs that block bladder contractions may be used to help with urinary control problems.
• Erythromycin, domperidone (Motilium), or metoclopramide (Reglan) may help with nausea and vomiting.
• Pain medications (analgesics) may work for some patients on a short-term basis, but in most cases they do not provide much benefit.
• Phosphodiesterase type 5 (PDE-5) drugs, such as sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are safe and effective for treating impotence in patients with diabetes.
• Capsaicin can be used topically to reduce pain.

Regular foot exams are important to identify small infections and prevent foot injuries from getting worse. If foot injuries go unnoticed for too long, amputation may be required.

Treatment relieves pain and can control some symptoms, but the disease generally continues to get worse.

• Injury to the feet due to loss of feeling
• Muscle breakdown and imbalance
• Poor blood sugar control due to nausea and vomiting
• Skin and soft tissue breakdown (ulceration) that may require amputation

In addition, neuropathy may mask angina, the warning chest pain for heart disease and heart attack.

Call your health care provider if you develop symptoms of diabetic neuropathy.

Tight control of blood sugar levels may prevent neuropathy in many people with type 1 diabetes, and may reduce the severity of symptoms.

In addition, regular foot care can prevent a small infection from getting worse. This is why no appointment for diabetes care is complete without a thorough foot examination.

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Vardi M, Nini A. Phosphodiesterase inhibitors for erectile dysfunction in patients with diabetes mellitus. Cochrane Database Syst Rev. 2007; Jan 24(1):CD002187.

Wong MC, Chung JW, Wong TK. Effects of treatments for symptoms of painful diabetic neuropathy: systematic review. BMJ. 2007; 335:87.

Hunt D. American Diabetes Association (ADA). Standards of medical care in diabetes--2008. Diabetes Care. 2008;31:S12-S54.