Diabetic neuropathy: types of nerve damage and warning signs

Nerves carry messages between your brain and the rest of your body. Over time, diabetes can damage them. This is called diabetic neuropathy, and it can affect the feet, the hands and even organs such as the heart and bladder. This article explains the types and warning signs based on information from the NIDDK and NHS.

What is diabetic neuropathy?

The NIDDK describes diabetic neuropathy as nerve damage caused by diabetes. Over time, high blood glucose and high blood fats such as triglycerides can injure nerves. The symptoms depend on the type of nerve that is affected.

The main types

The NIDDK describes four types:

• Peripheral neuropathy: usually affects the feet and legs, and sometimes the hands and arms. The NIDDK says it is very common, affecting about one-third to one-half of people with diabetes.
• Autonomic neuropathy: damages the nerves that control internal organs. This can affect heart rate, blood pressure, digestion, the bladder, sex organs, sweat glands and the eyes. It can also cause hypoglycemia unawareness, where a person does not feel low blood sugar.
• Focal neuropathy: damages a single nerve, most often in the hand, head, torso or leg. Carpal tunnel syndrome is the most common type.
• Proximal neuropathy: a rare and disabling condition affecting the hip, buttock or thigh. It usually affects one side of the body, and symptoms gradually improve over months or years.

Symptoms

The NIDDK says symptoms range from pain and numbness in the feet to problems with internal organs such as the heart and bladder. The NHS lists pain, tingling or numbness, sexual problems, and constipation or diarrhoea as signs that can point to nerve damage in people with type 2 diabetes. Numbness matters because, as the NIDDK explains on its foot care page, it can mean you do not notice cuts, blisters or a pebble in your shoe.

Why it matters for the feet

When feeling is reduced in the feet, small injuries can go unnoticed and may become serious. The NIDDK says reduced blood flow can make sores slow to heal and raise the risk of infection. Rarely, nerve damage changes the shape of the foot, a condition called Charcot's foot. Daily foot checks are therefore a key habit, as the NIDDK's foot care guidance explains.

Lowering your risk

The sources point to keeping blood glucose within the targets agreed with your care team. The NHS says the way to lower the risk of complications is to keep blood glucose as well controlled as possible, eat a balanced diet, exercise regularly, not smoke and attend all diabetes appointments and tests. The NIDDK's managing diabetes guidance adds blood pressure and cholesterol checks as part of routine care. These steps cannot promise that nerve damage will not occur, but they are what the agencies recommend.

Getting checked

The NIDDK says your health care team should check your feet at every visit and carry out a thorough foot exam, including sensation and pulses, at least once a year. If you already have loss of feeling, foot shape changes, peripheral artery disease or a history of ulcers or amputation, the NIDDK says a thorough exam should be done at every visit. Treatment for nerve symptoms depends on the type and is decided by a doctor.

Hypoglycemia unawareness

One form of autonomic neuropathy deserves special mention. Some people lose the usual warning signs of low blood sugar. The NIDDK says continuous glucose monitors that sound an alarm when levels fall can be especially useful for people with hypoglycemia unawareness or frequent lows. Talk with your care team if you think you are not feeling your lows.

When to see a doctor

Speak to your doctor or diabetes nurse if you notice pain, tingling or numbness in your feet or hands, sexual problems, or ongoing constipation or diarrhoea. The NIDDK advises calling your provider about a cut, blister or bruise on the foot that does not begin to heal within a few days, or skin that becomes red, warm or painful.

A foot infection that turns black or smells bad can signal gangrene, which is an emergency. Seek urgent help for any sudden weakness or numbness on one side of the body, confusion, or chest pain. In an emergency, call your local emergency number (112 in India, 911 in the United States).

This article is for education only and does not replace advice from your own doctor.