Diabetes is the single most common cause of neuropathy in the feet, but it’s far from the only one. Vitamin deficiencies, alcohol use, autoimmune diseases, infections, physical nerve compression, and certain medications can all damage the nerves that supply your feet. In roughly 25% to 46% of cases, no cause is ever identified even after thorough testing.
Why Neuropathy Hits the Feet First
Foot neuropathy follows a predictable pattern that doctors call a “stocking-glove” distribution. It starts in the toes and gradually creeps upward toward the ankles and calves before eventually reaching the hands. This isn’t random. Whatever is damaging your nerves, whether it’s high blood sugar, a toxin, or a nutritional gap, typically disrupts protein production inside the nerve cell body. That dysfunction shows up first at the farthest ends of the longest nerves in your body, which happen to run all the way from your lower spine to your toes. By the time you notice tingling or numbness in your fingertips, the damage in your feet has usually been progressing for a while.
Diabetes and High Blood Sugar
Persistently elevated blood sugar is the leading cause of peripheral neuropathy worldwide. The damage isn’t caused by one single mechanism. High glucose and abnormal fat metabolism trigger a cascade of problems inside nerve cells: mitochondria (the energy-producing structures inside cells) start malfunctioning, inflammation ramps up, and oxidative stress accumulates. Over time, this destroys the protective insulation around nerve fibers and damages the tiny blood vessels that feed them. The result is a slow, progressive loss of sensation that typically begins with numbness or burning in the toes and soles.
People with prediabetes can also develop neuropathy. Insulin resistance alone, even before blood sugar levels cross the diabetes threshold, appears to set these damaging pathways in motion.
Vitamin B12 and Other Nutritional Deficiencies
B12 plays a critical role in maintaining the myelin sheath, the insulating layer that wraps around nerve fibers and allows signals to travel quickly. When B12 drops too low, that insulation breaks down, leading to peripheral neuropathy and other neurological symptoms.
Here’s what makes B12 tricky: the standard clinical cutoff for “deficiency” may be set too low to protect your nerves. Research published in Neurology found that optimal neurological function, including nerve conduction speed and the ability to detect touch on the feet, required B12 levels around 400 pmol/L. That’s roughly 2.7 times higher than the conventional deficiency threshold most labs use. Low B12 is especially common in older adults, people on long-term acid-reducing medications, and those following strict vegan or vegetarian diets without supplementation.
Other nutritional causes include deficiencies in vitamins B1 (thiamine), B6, and E, as well as copper deficiency, which is rarer but can occur after gastric bypass surgery.
Alcohol Use
Heavy, long-term alcohol use damages foot nerves through what appears to be a double hit. Alcohol itself is directly toxic to nerve tissue, and chronic drinking also leads to poor nutrition, particularly thiamine (vitamin B1) deficiency. Both pathways contribute, and researchers haven’t been able to fully separate the two. The neuropathy that develops follows the same feet-first pattern as diabetic neuropathy, with burning pain, numbness, and difficulty with balance being common early complaints.
Chemotherapy and Other Medications
Certain cancer drugs are well known for causing peripheral neuropathy that concentrates in the feet and hands. The drug classes most likely to cause this include taxanes, platinum-based agents, vinca alkaloids, and some newer targeted therapies. These drugs damage neurons through different mechanisms, but the end result is similar: tingling, pain, or numbness that can start during treatment and sometimes persist for months or years after chemotherapy ends.
Cancer drugs aren’t the only medications that can cause foot neuropathy. Some antibiotics, anti-seizure drugs, and HIV medications carry neuropathy as a known side effect. If your symptoms started after beginning a new medication, that timing is worth paying attention to.
Autoimmune Diseases
When the immune system mistakenly attacks nerve tissue, the result can be rapid or slowly progressive neuropathy. Several autoimmune conditions are linked to foot neuropathy:
- Guillain-Barré syndrome causes sudden weakness and numbness that often starts in the feet and moves upward over days to weeks.
- Chronic inflammatory demyelinating polyneuropathy (CIDP) is a longer-lasting version that develops over months, with symptoms that wax and wane.
- Lupus, rheumatoid arthritis, and Sjögren’s syndrome can all cause neuropathy, sometimes through direct nerve inflammation and sometimes through blood vessel damage that cuts off the nerve’s supply.
- Vasculitis inflames blood vessel walls, which can starve nerves of oxygen and nutrients.
In some cancer patients, the immune system produces antibodies that attack nerves as a misdirected response to the tumor, a process called paraneoplastic syndrome. This can cause neuropathy even before the cancer itself is diagnosed.
Infections
Several infections can target or indirectly damage peripheral nerves. Shingles is one of the more common culprits. The virus reactivates along a nerve path and can leave behind lasting nerve pain called postherpetic neuralgia. Lyme disease, caused by tick-borne bacteria, can cause neuropathy weeks to months after the initial infection if left untreated. Hepatitis B and C both carry neuropathy risk, partly through the inflammation they cause and partly through immune complexes that deposit in nerve tissue. HIV can damage nerves directly, and some of the older antiretroviral medications used to treat it added to the problem.
Nerve Compression in the Foot
Not all foot neuropathy stems from a systemic cause. Sometimes the nerve is being physically squeezed at a specific point. Tarsal tunnel syndrome is one example: the tibial nerve passes through a narrow channel on the inner side of the ankle, and anything that crowds that space can compress the nerve and produce pain, tingling, or numbness along the bottom of the foot.
Common causes of this compression include ankle injuries (sprains, fractures, dislocations), ganglion cysts, bone spurs, varicose veins, and even foot structure. Both flat feet and unusually high arches can change the mechanics of the ankle enough to put pressure on the tibial nerve. Tarsal tunnel syndrome is worth considering when symptoms affect only one foot, since most systemic causes of neuropathy tend to be symmetrical.
How Neuropathy Is Detected
One of the most common screening tools is surprisingly simple. A thin nylon filament calibrated to deliver exactly 10 grams of force is pressed against the skin on the top of the big toe. If you can’t feel it, that indicates a meaningful loss of protective sensation. The test takes less than a minute per foot and is a standard part of diabetic foot exams, but it’s useful for screening any suspected neuropathy.
Beyond this, doctors typically use blood tests to check for diabetes, B12 levels, thyroid function, and markers of autoimmune disease or infection. Nerve conduction studies, which measure how quickly electrical signals travel along your nerves, can confirm the diagnosis and help pinpoint where the damage is occurring. In some cases, a small skin biopsy from the ankle or foot can reveal early nerve fiber loss before other tests pick it up.
When No Cause Is Found
Even after a thorough workup, 25% to 46% of peripheral neuropathy cases end up classified as idiopathic, meaning no clear cause is identified. This is more common in older adults. Some of these cases may involve metabolic factors that current testing doesn’t fully capture, such as borderline glucose intolerance or subtle nutritional shortfalls. The neuropathy itself is still real and still treatable in terms of symptom management. Not having a named cause can be frustrating, but it doesn’t change the options available for controlling pain and protecting your feet from injury related to reduced sensation.