Patient Guide to Diabetic Neuropathy

Diabetic Neuropathy: Causes and Symptoms

The many factors that lead to diabetic nerve pain

Diabetic peripheral neuropathy—DPN for short—is diabetes-related damage to nerves that sit near the surface of your skin. DPN usually affects the feet and the hands, but can also harm nerves in arms and legs. Approximately 50 percent of people with type 2 diabetes and 20% of those with type 1 diabetes develop this kind of nerve damage.1 DPN can be extremely painful—or cause numbness so that you have little feeling, especially in your feet.            

DPN damages two different types of nerves close to the surface of your skin. DPN can affect small nerves that protect your body by sending signals about pain and temperature changes to your brain. This condition can also attack large nerves that detect touch, pressure and help you keep your balance. 2 Symptoms are different for each type. Most people with DPN have damage to both types of nerves.

DPN usually affects extremities—feet, hands, legs and arms—where nerve fibers are the longest and most numerous. 3


Experts are still investigating exactly how diabetes harms and kills these nerve cells. “The causes remain unknown,” the American Diabetes Association noted in a definitive 2017 review. One thing is certain: The conventional wisdom—that high blood sugar is the cause—is just part of the story. New research is revealing a bigger cast of culprits. These include high cholesterol, high triglycerides (another blood fat), high blood pressure, obesity and smoking, according to a British research report in a widely-cited 2005 study that tracked 1,172 people with diabetes for seven years. 4 The threats are major:

  • Obesity and high triglycerides each doubled risk in people with diabetes in a 2013 University of Utah study of 218 people with type 2 diabetes. 5  Smoking increased risk by as much as 42% in a 2015 Harvard Medical School review of 38 studies on tobacco use and diabetic peripheral neuropathy that included more than 5,000 people. 6
  • High blood pressure increased risk 11 to 65% in a 2015 study 7 in the journal Medicine that tracked more than 37,000 people with type 2 diabetes for up to nine years.
  • In the same study, low levels of “good” HDL cholesterol and high levels of heart-threatening LDLs also boosted risk for diabetic peripheral neuropathy by up to 67%.

What’s behind the numbers? According to a 2017 review in the Journal of Diabetes Research, metabolic changes associated with diabetes and related health problems may damage nerve cells by boosting levels of rogue oxygen molecules called free radicals that attack the DNA inside cells, by zapping antioxidant compounds that normally protect cells from free radicals and by increasing inflammation.8  In addition, nerve fibers are extra-vulnerable to damage because the tiny blood vessels they rely on for oxygen and nutrients may also be damaged by high blood sugar, high blood pressure and unhealthy levels of blood fats.

Problems begin surprisingly early. In a 2015 University of Toronto study of 467 people, ages 45 to 64, about half of those with prediabetes or newly-diagnosed type 2 diabetes had early signs of peripheral neuropathy. 10 (Researchers measured how well nerves in their feet detected pain and vibration and also asked about symptoms.) Those with higher blood sugar levels were more likely to have nerve damage. In people with type 1 diabetes, whose high blood sugar problems are usually diagnosed very early, about 20% have peripheral neuropathy after 20 years. 11 Your risk may also rise with age, but even children and young adults with type 1 and type 2 diabetes have signs of peripheral neuropathy.

However the nerves get damaged, the end result is the same: they aren’t able to convey messages as well as they should to the brain, and they lose their ability to help you feel and move.

The good news? If you have type 1 diabetes, type 2 diabetes or prediabetes and do not yet have nerve damage, controlling blood sugar and taking other healthy steps can help prevent it from happening. For people with type 1 diabetes, tight glucose control can cut risk for DPN by 78%; for those with type 2, it may reduce risk 5-9%. 12 Why the big difference in risk for neuropathy between those with type 1 and type 2 diabetes? Experts believe4 that because people with type 1 diabetes are diagnosed earlier in life and after only having the condition for a short time, there is a smaller period of time that they are exposed to high blood sugar levels, and therefore less time for sugar to damage nerves. Meanwhile, people diagnosed with type 2 diabetes have often had high sugar levels for years (nerve damage can begin in the prediabetic stage), which can mean lots of nerve damage by the time a diagnosis is made. Additionally, other factors such as being overweight, smoking, having high cholesterol, high blood pressure, and/or high triglycerides also up one's risk for nerve damage. 

Right now there’s no cure for nerve damage. However, if you already already have nerve damage, getting healthy and/or staying healthy can help prevent the progression of nerve damage. You may need medication to effectively control the pain, according to the American Diabetes Association (ADA). In fact, the ADA states in a 2017 position paper on nerve damage that there’s “no compelling evidence” that blood sugar control and a healthy lifestyle can ease the pain. But some experts say keeping blood sugar under control may help some people. 13, 14 Blood sugar “spikes” may aggravate the discomfort, for example.15  And there’s exciting early evidence that regular exercise helped nerves regenerate somewhat in people with type 2 diabetes and peripheral neuropathy in a 2014 University of Utah study of 100 women and men, in their 50s and 60s. 16 And a healthy diet plus exercise reduced nerve pain and helped nerves recover somewhat in a 2006 University of Utah study of 32 women and men in their 50s and 60s with prediabetes and early nerve damage. 17 And in a 2015 study of 34 women and men, also in their 50s and 60s, with type 2 diabetes and diabetes nerve pain, those who followed a strictly vegan (plant-based) eating plan for 20 weeks lost about 15 pounds apiece, reduced their blood sugar and reported less nerve pain. 18 

Peripheral Neuropathy Symptoms

In general, diabetic neuropathy symptoms develop gradually; they may seem like minor and infrequent pains at first, but as the nerves become more damaged, symptoms may grow. Talk with your doctor if you notice any symptoms or changes, even if they bother you just once in a while or seem insignificant. You can get relief -- and may need help preventing complications such as foot infections.

Symptoms of DPN include:

  • Pain
  • Burning, stabbing or electric-shock sensations
  • Numbness (loss of feeling)
  • Tingling
  • Muscle weakness
  • Poor coordination
  • Muscle cramping and/or twitching
  • Insensitivity to pain and/or temperature
  • Extreme sensitivity to even the lightest touch
  • Symptoms get worse at night. 19, 20 

Damage to small nerve fibers causes pain – for some, even wearing socks and shoes or the touch of sheets and blankets on their feet at night is excruciating. Damage to large fibers causes tingling, numbness, weakness and balance/coordination problems.  It may feel as if your feet are wrapped in extremely thick socks. Up to half of all people with neuropathy don’t notice any symptoms at all – or don’t realize the cause. That can be dangerous. If your feet are numb, for instance, you may not notice small scrapes, blisters or cuts that can lead to serious infections and even to the need for amputation. 21


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Diabetic Neuropathy: Your Diagnosis
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