Diabetic Neuropathy: What It Is, Symptoms, and Forms

Tingling in the toes and burning in the soles of the feet—this is often how diabetic neuropathy begins, nerve damage in people with diabetes mellitus. What this condition is, what forms and symptoms it has, and how it is recognized—in the material below.

What diabetic neuropathy is

Diabetic neuropathy is nerve damage caused by diabetes. The pathological process affects all types of nerve fibers: sensory, motor, and autonomic, so manifestations can be very different—from pain and numbness in the feet to disorders of the heart and bladder. Central and peripheral neuropathy are distinguished. The most common peripheral form is distal symmetric sensorimotor polyneuropathy, which is usually what is called diabetic polyneuropathy.

Diabetic neuropathy is present in more than half of people with diabetes, peripheral in about one-third to one-half, autonomic on average in 20–40%.

Why nerves are damaged in diabetes mellitus

In diabetes, blood glucose levels are elevated, and over time this damages the nerve sheath or the small vessels that supply nerves with oxygen. High blood levels of fats, particularly triglycerides, also play a role. A damaged nerve may stop sending signals altogether, or may send them slowly or at the wrong time—hence the strange sensations and unusual body reactions.

Symptoms of diabetic polyneuropathy

Symptoms depend on which nerves are affected. The typical set in polyneuropathy looks like this:

• numbness in the hands, legs, or feet;
• shooting pain, burning, or tingling;
• nausea, vomiting, constipation, or diarrhea;
• problems with sexual function and urination;
• dizziness when changing body position quickly.

This list does not mean a person will have everything at once: some develop tingling first, others dizziness. If you recognize at least one item and you have a diagnosis of diabetes, tell your doctor about the symptom.

Leg neuropathy in diabetes

Peripheral neuropathy usually begins in the feet and lower legs, sometimes involving the hands and forearms. Numbness manifests as reduced sensation in the hands, legs, or feet. Pain may be burning or shooting. Less commonly, proximal neuropathy occurs—damage to the thigh, buttock, or hip region; it is rare and disabling, usually unilateral, and its symptoms gradually improve over months or years. Focal neuropathies affect individual nerves—most often in the hand, head, trunk, or leg; the most common of these are tunnel syndromes, such as carpal tunnel.

Painful and autonomic diabetic neuropathy

The painful form is when damaged nerves cause pain: burning or shooting. Autonomic diabetic neuropathy concerns the nerves that control internal organs: the heart and vessels, digestion, the bladder, genital organs, sweat glands, and eyes. It manifests as slowed adaptation of vision when moving from a bright room to a dark one, impaired sweating in nearly half of people with diabetes, constipation and diarrhea, although pronounced diarrheal symptoms occur in only 1% of patients. Cardiac autonomic neuropathy is distinguished separately—impaired autonomic regulation of the cardiovascular system. One of the consequences is loss of hypoglycemia awareness: a person does not feel the onset of low sugar. Autonomic neuropathy is an independent prognostic factor for mortality in diabetes.

How it is diagnosed and when a doctor is needed

The diagnosis is made based on examination results and nerve tests, and if autonomic disorders are suspected, autonomic testing is performed. During the appointment, the doctor assesses symptoms, examination data, and test results. If numbness, burning, or shooting pain in the feet, dizziness on standing up, or problems with urination or digestion appear, this is a reason to see a doctor and discuss examination.

Diabetic neuropathy itself is not a reason to call an ambulance. You should call 103 or 112 if signs of stroke or heart attack appear—conditions that are life-threatening.

This material is for reference: it explains what is happening and what to ask the doctor, but does not replace consultation—the decision on examination remains with your doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer