Peripheral neuropathy in the feet happens when nerves outside the brain and spinal cord become damaged, and diabetes is the single most common cause, accounting for 32% to 53% of all cases. But dozens of other conditions can trigger it too, from vitamin deficiencies to autoimmune disorders to the side effects of cancer treatment. About 2.4% of the general population has some form of peripheral neuropathy, and that number climbs above 8% in people over 55.
Diabetes and Chronic High Blood Sugar
Persistently elevated blood sugar is the leading driver of nerve damage in the feet. The harm isn’t from a single spike but from years of metabolic stress that compounds over time. High glucose and abnormal blood lipids set off a cascade of problems inside nerve cells: the energy-producing structures in those cells (mitochondria) start malfunctioning, inflammation builds, and harmful oxygen molecules accumulate faster than the body can neutralize them. The end result is direct damage to the neurons and the support cells surrounding them.
There’s also a vascular component. Diabetes reduces the permeability of tiny blood vessels that feed peripheral nerves. Research on the tibial and peroneal nerves, the two major nerves running into the foot, found that it’s this reduced permeability, not a decrease in blood volume, that starves nerves of oxygen. Over time, the oxygen-deprived nerve fibers degrade, starting at the longest ones first. That’s why the feet are almost always affected before the hands.
Insulin resistance adds another layer of harm. When insulin signaling is disrupted, the body loses some of its ability to repair damaged nerve fibers and instead accelerates the death of injured cells. This means that even when blood sugar is only moderately elevated, the combination of poor repair mechanisms and ongoing metabolic damage can push neuropathy forward.
Vitamin and Nutritional Deficiencies
Vitamin B12 plays a central role in maintaining the protective coating around nerve fibers, called the myelin sheath. When B12 drops too low, that coating breaks down, and the exposed nerves misfire or stop transmitting signals altogether. The standard clinical cutoff for B12 deficiency is relatively low, but research published in Neurology found that optimal nerve function requires B12 blood levels roughly 2.7 times higher than that traditional threshold. Older adults with levels below about 390 to 410 pmol/L showed measurably slower nerve conduction and faster cognitive decline compared to those above it.
This means you can technically fall within the “normal” range on a lab test and still have B12 levels low enough to affect your nerves. People at highest risk include those over 60 (who absorb less B12 from food), strict vegans, and anyone taking long-term acid-reducing medications, which interfere with B12 absorption in the stomach.
Other nutritional gaps matter too. Thiamine (vitamin B1), vitamin E, and copper deficiencies can all produce neuropathy in the feet, though B12 deficiency is by far the most common nutritional cause.
Alcohol-Related Nerve Damage
Chronic heavy drinking damages foot nerves through two separate mechanisms that often occur simultaneously. First, ethanol itself is directly toxic to nerve tissue. The body can handle moderate amounts, but sustained heavy use gradually degrades nerve fibers. Second, alcohol suppresses appetite and impairs the gut’s ability to absorb nutrients from food, leading to deficiencies in key vitamins, especially thiamine. Since thiamine is essential for nerve function, this creates a compounding problem where the nerves are being poisoned and starved at the same time.
The resulting neuropathy typically starts as burning or tingling in the soles of the feet and progresses upward. It develops slowly enough that many people don’t connect their symptoms to their drinking habits until the damage is well established.
Chemotherapy and Medication Side Effects
Certain cancer drugs are notoriously hard on peripheral nerves. Taxanes and platinum-based agents carry the highest risk, but other classes including vinca alkaloids, thalidomide, and bortezomib can also cause what’s known as chemotherapy-induced peripheral neuropathy. The numbers are striking: roughly 68% of patients experience neuropathy one month after completing treatment, 60% still have it at three months, and about 30% are still dealing with symptoms six months or more later.
The damage typically starts in the toes and feet because the longest nerve fibers are the most vulnerable. Symptoms range from numbness and tingling to sharp pain and difficulty with balance. For some patients, the neuropathy resolves gradually after treatment ends. For others, it becomes a permanent side effect.
Beyond chemotherapy, several other medications can cause peripheral neuropathy with prolonged use. These include certain antibiotics (particularly fluoroquinolones and metronidazole), some heart rhythm drugs, and antiretroviral medications used to treat HIV.
Autoimmune and Inflammatory Conditions
The immune system can sometimes turn against the body’s own nerve tissue. In chronic inflammatory demyelinating polyneuropathy (CIDP), the immune system attacks the myelin sheath surrounding peripheral nerves, slowing or blocking signal transmission. CIDP causes progressive weakness and reduced sensation in both the arms and legs, developing over at least two months. About 90% of people with CIDP show elevated protein levels in their spinal fluid, a hallmark of the inflammatory process at work.
Other autoimmune conditions linked to foot neuropathy include lupus, rheumatoid arthritis, Sjögren’s syndrome, and vasculitis (inflammation of blood vessels that supply nerves). In these cases, the neuropathy is a downstream consequence of the broader immune dysfunction rather than a disease in its own right.
Infections That Target Nerves
Several infections can directly damage peripheral nerves. Lyme disease, caused by a tick-borne bacterium, can produce what’s called radiculoneuropathy during early disseminated infection. This causes numbness, tingling, shooting pain, or weakness in the arms or legs. Shingles, a reactivation of the chickenpox virus, can leave behind persistent nerve pain (postherpetic neuralgia) in the affected area. HIV itself can damage peripheral nerves, as can hepatitis C.
Inherited Neuropathy
Charcot-Marie-Tooth disease is the most common inherited form of peripheral neuropathy. It’s caused by gene mutations that either damage the nerve fibers directly or break down the protective myelin coating around them. The disease tends to show up in the feet first, and the physical signs are distinctive: unusually high arches, hammertoes, weakness in the ankles, and foot drop (difficulty lifting the front of the foot). Over time, the muscles in the lower legs shrink noticeably, sometimes giving the calves the appearance of an upside-down champagne bottle.
These gene mutations most often run in families, though new mutations can appear in people with no family history. Because the condition is progressive, many people live with mild symptoms for years before the nerve damage becomes functionally limiting.
Idiopathic Neuropathy: No Identified Cause
In a significant number of cases, no specific cause is ever identified despite thorough testing. Estimates vary, but roughly 20% to 30% of peripheral neuropathy cases are classified as idiopathic. Many of these patients have prediabetes or metabolic syndrome that hasn’t been formally diagnosed, which may account for at least some of the “unexplained” cases. Age itself is a risk factor: nerve fibers naturally degrade over decades, and the longest ones running to the feet are the first to show wear.
How the Cause Is Identified
Pinpointing the specific cause usually starts with blood work to check for diabetes, vitamin deficiencies, thyroid problems, and markers of autoimmune disease. Nerve conduction studies measure how fast electrical signals travel through the nerves in your feet. A normal sural nerve (the main sensory nerve tested in the lower leg) conducts signals at 40 meters per second or faster. Speeds below that threshold suggest damage.
If standard testing doesn’t reveal a cause, additional steps may include checking for antibodies associated with specific autoimmune neuropathies, genetic testing for inherited conditions like Charcot-Marie-Tooth disease, or, in some cases, a small nerve biopsy. The type of nerve damage, whether it affects the protective myelin coating or the nerve fiber itself, often points toward different categories of causes and helps narrow the diagnosis.