Causes
Diabetic neuropathy
Diabetes is the most common cause of nerve damage in the developed world, and the feet are where it shows first. The useful part is not the diagnosis — it is knowing which of the four patterns you have, and which one is quietly dangerous.
Written by the Managing Neuropathy editorial team under the direction of Dr. Tom Biernacki, DPM, FACFAS · Clinical review pending · Last updated 6 September 2026
The short answer. Diabetic neuropathy comes in four forms. The common one is a symmetric loss of sensation that creeps up from the toes. Glucose control is the only intervention that reliably slows it, and it slows it rather than reverses it. The danger is not the numbness — it is that a foot which cannot feel does not report injury, and an unnoticed injury is how ulcers and amputations begin.
Why diabetes damages nerves
Nerves are supplied by very small blood vessels, and sustained high glucose damages small blood vessels. The nerve fibers furthest from the body have the longest and most fragile supply line, so they fail first — which is why this begins in the toes and works upward rather than starting anywhere else.
Two things about the timing surprise people. It begins before diagnosis: nerve damage is found in people with prediabetes and impaired glucose tolerance, sometimes years before a diabetes diagnosis is made. And it is often painless from the start, so the absence of symptoms is not evidence that nothing is happening. That is the argument for having the feet examined on a schedule rather than when something hurts.
The four patterns
1. Distal symmetric polyneuropathy — the common one
Both feet, starting in the toes, spreading upward over years, eventually reaching the hands. Numbness, a walking-on-cotton sensation, unsteadiness in the dark, burning or electric pain that is worse at night. This is what most people mean by diabetic neuropathy, and it accounts for the great majority of cases. Reading the pattern is covered in detail here.
2. Autonomic neuropathy — the one that gets missed
The nerves that run the body without your involvement: heart rate, blood pressure, sweating, digestion, bladder, sexual function. Because the symptoms do not look like nerve symptoms, they get attributed to other things.
Worth mentioning to a clinician: dizziness or faintness on standing; a resting heart rate that no longer varies; feeling full quickly or unpredictable blood sugars after meals; bladder changes; and, on the feet specifically, skin that has become dry and cracked because it no longer sweats. Autonomic involvement also blunts the warning symptoms of low blood sugar and of a heart attack, which is the reason it matters out of proportion to how it feels.
3. Focal neuropathy — one nerve, suddenly
A single nerve, often compressed at a specific point: carpal tunnel at the wrist, an ulnar nerve at the elbow, a peroneal nerve at the knee causing sudden difficulty lifting the front of the foot, or a cranial nerve producing double vision or one-sided facial weakness. Onset is abrupt and it is frequently painful. Many focal neuropathies improve over weeks to months, and several are treatable, so this pattern is worth identifying rather than absorbing into the general diagnosis.
4. Proximal neuropathy — thighs and hips
Uncommon, usually in older adults with type 2 diabetes: severe pain in the hip, thigh or buttock, followed by weakness in the leg and often weight loss. It typically affects one side first. It tends to improve, and it is emphatically not something to wait out at home — it needs to be seen, because the alternatives on the list of possible causes are serious.
What glucose control does
It is the intervention with the strongest evidence for slowing progression, and the evidence is stronger in type 1 than in type 2 — where nerve outcomes are influenced by blood pressure, lipids and other vascular factors as well.
What it does not do is restore fibers already lost. This produces the most common disappointment in the whole condition: someone brings their A1c down substantially, feels no better, and concludes the effort was pointless. What they have actually bought is the damage they did not go on to accumulate — real, valuable, and invisible.
One genuine oddity is worth knowing about in advance. A rapid improvement in glucose control can be followed by a temporary increase in nerve pain. It is recognized, it is not a sign that control was the wrong idea, and it is a reason to tell your clinician rather than to abandon the effort.
The metformin footnote
Long-term metformin is associated with reduced vitamin B12 absorption, and B12 deficiency causes a neuropathy of its own that looks very much like the diabetic one. It is correctable, and it is missed when everyone assumes the diabetes explains everything. Periodic B12 checking in people on long-term metformin is recommended, and it is a reasonable and specific thing to ask for by name.
The complication that matters
Numbness itself does not harm you. The sequence it permits does.
A foot with loss of protective sensation does not report a blister, a stone, a seam, a too-short toenail or a burn. The injury goes unnoticed, becomes a wound, and heals badly if circulation is also reduced. The great majority of non-traumatic lower-limb amputations are preceded by a foot ulcer — which means the chain is long, slow, and interruptible at every link.
Charcot foot deserves its own warning. A foot that suddenly becomes warm, red and swollen, often without any injury you can recall, in someone with neuropathy, is a medical urgency — not a sprain to walk off. Bones can fracture and collapse in a foot that cannot feel it happening, and the resulting deformity is far harder to manage than the early phase. Warm, swollen, changed shape, no clear injury: get it looked at within days, not weeks.
What actually prevents harm
Good light, tops, soles and between every toe. A mirror or a phone camera for the parts you cannot see. This substitutes your eyes for the warning system you have lost. The routine is here.
No heating pads, hot water bottles, electric blankets, hot soaks or radiators. Burns happen at temperatures that feel mild, and they happen to people trying to soothe their symptoms.
Indoors included. Shake out shoes before putting them on. Most of the injuries that start an ulcer are trivial to a foot that can feel.
You cannot judge fit with insensate feet. Medicare covers therapeutic shoes and inserts for qualifying patients, which most people are never told. How that benefit works is here.
At least annually with diabetes, and more often once protective sensation is reduced. A monofilament test takes a minute and tells you which risk category you are in.
Days, not weeks. A wound seen early is a dressing; a wound seen late is a different conversation.
Treating the symptoms
Painful diabetic neuropathy is one of the better-studied neuropathic pains, and several prescription medicines have real evidence behind them. They reduce pain without slowing the damage, which is worth having on its own terms as long as you know which column it sits in. The treatment landscape, including how to evaluate an expensive clinic package, is here.
Common questions
Can diabetic neuropathy be reversed?
Fibers already lost do not return. Improvement is possible early, and in people with prediabetes, intensive lifestyle change has shown some benefit for nerve measures. The realistic goal in established disease is to slow it, treat the pain, and prevent complications.
How quickly does it progress?
Usually over years, and closely tied to glucose control, blood pressure and lipids. Rapid progression over weeks is not typical, and is a reason to be re-examined rather than to assume the diabetes explains it.
I have prediabetes. Is this relevant to me?
Yes. Nerve damage is found in impaired glucose tolerance, and this is the point in the story where lifestyle change has the most to offer.
My feet are numb but not painful. Is that better?
More comfortable, not safer. Painless numbness carries the same ulcer risk and removes the symptom that would otherwise send you to a clinician. It is the pattern that most needs a daily foot check.
Can I soak my feet?
Soaking is generally discouraged in diabetes: it softens the skin, and hot water burns a foot that cannot judge temperature. Wash, dry thoroughly — particularly between the toes — and moisturize the skin while avoiding the web spaces.
Related reading
Neuropathy in the feet: the full picture · Numb toes: reading the pattern · Shoes and the Medicare benefit · Diabetic socks, honestly · The daily foot check · Treatment options
Sources and further reading: American Diabetes Association Standards of Care, sections on neuropathy, retinopathy and foot care, including annual foot examination, glycaemic control to slow progression, and periodic B12 assessment with long-term metformin. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), diabetic neuropathy types and diabetic foot care. National Institute of Neurological Disorders and Stroke (NINDS), peripheral neuropathy.
This page is general education and is not a diagnosis, a treatment plan, or advice to start or stop any medicine. Clinical review by Dr. Biernacki is pending; the review date will be shown here once complete.
For our Michigan neighbors
When was your last
foot examination?
Protective sensation testing, a risk category, and a plan take one visit. Dr. Biernacki’s Michigan practice sees diabetic feet every week.
Everywhere else, take this page to your own clinician.
Dr. Tom Biernacki, DPM, FACFAS is a double board-certified foot and ankle surgeon (ABFAS and ABPM) and a Fellow of the American College of Foot & Ankle Surgeons. He is the founder of Balance Foot & Ankle in Howell and Bloomfield Township, Michigan, where peripheral neuropathy, diabetic foot risk and loss of protective sensation are part of his weekly clinic. His patient education videos have drawn more than 950,000 subscribers on YouTube. He writes Managing Neuropathy to put the explanation he gives in the exam room in front of the people who cannot get to one — including when a product is worth buying and when it is not.