Neuropathy in the legs happens when peripheral nerves, the long fibers connecting your spinal cord to your feet and lower limbs, become damaged or diseased. Diabetes is the single most common cause, but dozens of other conditions can trigger it, from vitamin deficiencies and alcohol use to autoimmune disorders and certain medications. In many cases, more than one factor is at work simultaneously.
Why the Legs Are Affected First
Peripheral neuropathy almost always starts in the feet and works upward. This isn’t random. The nerves supplying your toes are the longest in your body, stretching from a tiny cluster of nerve cells near your spine all the way down to your feet. These extremely long fibers are vulnerable at their most distant end because they depend on a steady supply of nutrients and oxygen transported along their entire length. When something disrupts that supply, whether it’s high blood sugar, a toxin, or inflammation, the farthest tips of the nerve suffer first. This creates the characteristic “stocking” pattern of numbness, tingling, or pain that begins in the toes and gradually creeps up the calves.
Diabetes and High Blood Sugar
Chronically elevated blood sugar is the leading cause of leg neuropathy worldwide. The damage isn’t from a single mechanism but from a cascade of overlapping problems. Excess glucose gets converted into a sugar alcohol called sorbitol inside nerve cells, depleting the protective antioxidants those cells need to survive. At the same time, glucose reacts with proteins to form harmful compounds called advanced glycation end-products, which accumulate directly in nerve fibers and the tiny blood vessels feeding them.
Those small blood vessels are critical. In diabetes, the walls of the microscopic vessels inside nerves thicken and deteriorate, reducing blood flow and starving nerve fibers of oxygen. The nerve essentially suffers a slow, ongoing shortage of fuel. Meanwhile, mitochondria inside nerve cells begin to malfunction, triggering a self-destruct process in the cells themselves. The combined effect of toxic metabolic byproducts and impaired blood supply is what makes diabetic neuropathy progressive: the longer blood sugar stays elevated, the more nerve fibers degenerate from the toes upward.
Alcohol Use
Heavy, long-term alcohol consumption damages leg nerves through two separate pathways that often overlap. The first is nutritional: alcohol impairs the absorption of thiamine (vitamin B1) in the gut, drains the liver’s thiamine stores, and blocks the chemical step that converts thiamine into its active form. People who drink heavily also tend to eat poorly, compounding the deficiency.
The second pathway is direct toxicity. Ethanol is broken down into acetaldehyde, a highly reactive compound that damages proteins, disrupts DNA repair, and impairs the energy-producing machinery inside cells. Animal studies confirm that nerve degeneration occurs even when thiamine levels are kept normal, and human data show a dose-dependent relationship: the more alcohol consumed over a lifetime, the worse the neuropathy. The two forms also feel different. Pure alcohol-related neuropathy tends to progress slowly with burning pain and impaired sensitivity to sharp or hot stimuli. Thiamine-deficiency neuropathy, by contrast, is more likely to cause muscle weakness and can worsen quickly.
Vitamin B12 Deficiency
Vitamin B12 plays an essential role in building and maintaining myelin, the insulating sheath that wraps around nerve fibers and allows signals to travel quickly. Without enough B12, the body produces abnormal fatty acids that lead to faulty or deteriorating myelin. At the same time, a lack of B12 causes a toxic amino acid called homocysteine to accumulate, which directly damages neurons.
Levels below about 148 pg/mL are considered very low, but neuropathy has been associated with levels that many labs would still call borderline. A systematic review of 32 studies found that neuropathy risk increased roughly 50% in people with low B12 levels. The resulting nerve damage is primarily sensory, producing numbness and tingling in the legs and feet. B12 deficiency is especially common in older adults, people taking long-term acid-reducing medications, and those following strict vegan diets without supplementation. Other B vitamins, including B6 and folate, are also involved in nerve maintenance, though B12 deficiency is the most frequent culprit.
Chemotherapy and Other Medications
Certain cancer treatments are notorious for causing neuropathy in the legs and feet, a condition called chemotherapy-induced peripheral neuropathy. It follows the same “stocking and glove” pattern as other forms, with the feet typically affected before the hands. Symptoms can begin days after the first infusion and are dose-dependent, meaning the risk climbs with each additional treatment cycle.
Platinum-based drugs carry some of the highest rates. With cisplatin, neuropathy develops in up to 92% of patients at higher cumulative doses. Oxaliplatin causes acute, temporary nerve symptoms in 65 to 98% of patients, with chronic neuropathy developing in roughly 10% at moderate cumulative doses and up to 50% at the highest doses. Taxanes like paclitaxel cause neuropathy in 11 to 87% of patients depending on the regimen. Vinca alkaloids, particularly vincristine, cause sensory symptoms and painful tingling first, with weakness following at higher doses. Thalidomide, used for certain blood cancers, also carries dose-dependent nerve toxicity. For many of these drugs, symptoms improve after treatment stops, but some patients experience lasting damage.
Beyond chemotherapy, other medications linked to leg neuropathy include certain antibiotics (particularly fluoroquinolones and metronidazole), some HIV medications, and high-dose vitamin B6 supplements, which paradoxically can cause the same type of nerve damage that B6 deficiency causes.
Autoimmune and Inflammatory Conditions
The immune system can mistakenly attack peripheral nerves, stripping away their myelin coating or damaging the nerve fibers themselves. One well-known example is chronic inflammatory demyelinating polyneuropathy (CIDP), which typically begins with tingling and weakness in the legs along with difficulty walking. On examination, muscle weakness affects both sides of the body and involves muscles close to the trunk as well as in the feet, with reduced or absent reflexes. CIDP is most common between ages 40 and 60, affects men more often, and progresses over at least 8 weeks, distinguishing it from Guillain-Barré syndrome, which peaks faster.
Other autoimmune conditions that can cause leg neuropathy include lupus, rheumatoid arthritis, Sjögren’s syndrome, and vasculitis, which inflames the blood vessels supplying nerves. In each case, the immune system’s attack reduces blood flow to the nerve or directly destroys nerve tissue.
Nerve Compression and Physical Injury
Not all leg neuropathy is systemic. Sometimes the problem is mechanical: a single nerve gets pinched or compressed at a specific point. The most common example in the leg is peroneal nerve compression, where the nerve wraps around the bony knob just below the outer side of the knee. Habitual leg crossing, prolonged bed rest, tight casts, or significant weight loss (which removes the fat pad protecting the nerve) can all trigger it. Symptoms include foot drop, numbness over the top of the foot, and weakness when trying to lift the toes.
Deeper in the leg, the superficial peroneal nerve can get trapped as it exits the outer compartment of the lower leg, and the deep peroneal nerve can be compressed between structures at the top of the ankle. Tarsal tunnel syndrome, similar to carpal tunnel but at the inner ankle, is another entrapment that causes burning or tingling along the sole of the foot. Traumatic injuries, including fractures, dislocations, and surgical complications, can also sever or stretch nerves in the leg.
Infections
Several infections can damage peripheral nerves. Lyme disease, caused by bacteria transmitted through tick bites, can affect the peripheral nervous system during its early disseminated stage, producing numbness, tingling, shooting pain, or weakness in the arms and legs. Shingles, a reactivation of the chickenpox virus, can cause intense burning pain along a single nerve’s territory, and the pain sometimes persists for months or years after the rash heals (postherpetic neuralgia). HIV can cause neuropathy both from the virus itself and from certain antiretroviral medications. Hepatitis C has also been associated with peripheral nerve damage, potentially through immune-mediated inflammation of small blood vessels.
Other Contributing Causes
Kidney disease allows toxins to accumulate in the blood that would normally be filtered out, and these uremic toxins are directly harmful to nerve fibers. Hypothyroidism causes fluid retention and tissue swelling that can compress nerves, along with metabolic changes that impair nerve function. Exposure to heavy metals like lead, mercury, and arsenic damages nerves through oxidative stress, as do industrial solvents and certain pesticides.
Hereditary neuropathies, the most common being Charcot-Marie-Tooth disease, cause progressive weakness and sensory loss in the legs starting in childhood or early adulthood. These genetic conditions affect the structure of myelin or the nerve fiber itself and tend to run in families with a pattern of high arches, hammertoes, and difficulty running.
How the Cause Is Identified
Because so many conditions can produce identical symptoms, pinpointing the cause typically involves blood tests (checking glucose levels, B12, thyroid function, kidney markers, and inflammatory indicators), followed by nerve conduction studies and electromyography if the diagnosis is unclear. Nerve conduction testing sends small electrical pulses along a nerve and measures how fast the signal travels and how strong it is. If the signal speed drops but its strength stays normal, the problem is likely damage to the myelin insulation, as seen in CIDP or early compression injuries. If the signal strength drops instead, nerve fibers themselves are dying off, which is more typical of diabetic, toxic, or nutritional neuropathy.
Electromyography, which records electrical activity in the muscles, can detect signs of ongoing nerve fiber loss, such as spontaneous twitching in resting muscle that shouldn’t be firing on its own. Together, these tests help distinguish between different types and severities of nerve damage, guiding treatment toward the underlying cause rather than just the symptoms. In a meaningful percentage of cases, no clear cause is found even after thorough testing, a situation classified as idiopathic neuropathy. These cases are still managed with symptom control and monitoring for any emerging underlying condition.