Peripheral neuropathy has dozens of known causes, but diabetes is the single most common one. In roughly 30% of cases, no cause is ever identified, a condition called idiopathic neuropathy. The remaining cases trace back to a mix of metabolic problems, toxic exposures, infections, autoimmune diseases, inherited conditions, and physical injuries to nerves.
Diabetes and High Blood Sugar
Chronically elevated blood sugar is the leading cause of peripheral neuropathy worldwide. Among people with diabetes, the prevalence ranges from 7% within the first year of diagnosis to 50% in those who have had the disease for 25 years or more. If subtle, subclinical nerve changes are counted, that number may exceed 90%.
The damage happens through a cascade of metabolic events triggered by prolonged high blood sugar. Excess glucose gets converted into a sugar alcohol called sorbitol, which builds up inside nerve cells because it can’t easily pass through cell membranes. This creates swelling and, eventually, cell death. At the same time, high blood sugar ramps up oxidative stress and inflammation inside nerve fibers, gradually degrading them from the ends inward. That’s why diabetic neuropathy almost always starts in the toes and feet before working its way up.
Alcohol Use
Heavy, long-term drinking damages peripheral nerves through two overlapping mechanisms. Ethanol itself is directly toxic to nerve fibers. Studies in both animals and humans have shown that nerve degeneration occurs even when nutrition is adequate, and the severity of damage correlates with the total lifetime dose of alcohol consumed. At the same time, chronic alcohol use impairs absorption of B vitamins, especially thiamine (B1), which nerves need to function. Most cases of alcoholic neuropathy involve both direct toxicity and nutritional deficiency working together, though researchers have confirmed that malnutrition alone is not a prerequisite for the condition to develop.
Vitamin Deficiencies
Vitamin B12 plays a central role in maintaining the protective myelin sheath that insulates nerve fibers. When B12 levels drop, that sheath breaks down, and signals traveling through the nerves slow or misfire. The typical symptoms are tingling, numbness, unsteady walking, and limb weakness. B12 deficiency is especially common in older adults, people who follow strict vegan diets, and those taking long-term acid-reducing medications that interfere with absorption.
Other nutritional gaps can cause similar problems. Thiamine (B1) deficiency damages nerves and is frequently seen alongside alcohol use disorders or severe malnutrition. Vitamin B6 is unusual: both deficiency and excess can trigger neuropathy. Vitamin E deficiency, though less common, also contributes to nerve degeneration over time.
Chemotherapy and Medications
Several classes of cancer drugs are well-established causes of peripheral neuropathy. Platinum-based drugs like oxaliplatin, taxanes like docetaxel, vinca alkaloids like vincristine, and myeloma treatments like bortezomib all carry significant risk. Symptoms can appear within hours to days of a treatment session and typically start as tingling or numbness in the hands and feet. For some patients, the neuropathy fades after treatment ends. For others, it persists for months or years.
Cancer drugs aren’t the only medications involved. Certain antibiotics, antivirals, and heart rhythm medications can also cause nerve damage, particularly at high doses or over long treatment courses.
Autoimmune and Inflammatory Diseases
When the immune system mistakenly attacks nerve tissue, the result can be rapid or slowly progressive neuropathy. Guillain-Barré syndrome is the most dramatic example: the immune system strips the myelin sheath from peripheral nerves over days to weeks, causing weakness that can spread from the legs to the arms and respiratory muscles. Chronic inflammatory demyelinating polyneuropathy (CIDP) follows a similar pattern but develops over months rather than days.
Neuropathy also complicates many other autoimmune conditions. In lupus, it usually appears as mild, symmetrical tingling and numbness. In Churg-Strauss syndrome, an inflammatory blood vessel disease, peripheral neuropathy affects 50 to 80% of patients, often in an asymmetric pattern where isolated nerves are damaged one at a time. Sjögren’s syndrome, rheumatoid arthritis, and sarcoidosis can all trigger nerve involvement as well. The underlying mechanism often involves inflamed blood vessels cutting off the blood supply to nerves, starving them of oxygen.
Infections
Several bacterial and viral infections target the peripheral nervous system directly. HIV is a major cause globally: peripheral neuropathy has become the most common neurological complication in people living with HIV, driven by the virus itself and, in some cases, by antiretroviral medications used to treat it.
Shingles, caused by reactivation of the chickenpox virus, can leave behind a painful condition called postherpetic neuralgia in which damaged sensory nerves continue firing pain signals long after the rash heals. Hepatitis C can cause neuropathy through direct viral effects or by triggering blood vessel inflammation. Lyme disease, caused by a tick-borne bacterium, occasionally leads to nerve damage, though chronic polyneuropathy from Lyme remains rare. Leprosy, still present in parts of the world, causes a complex pattern of nerve damage through direct bacterial invasion and immune responses within nerve tissue.
Toxins and Heavy Metals
Workplace and environmental exposures account for a meaningful share of neuropathy cases. Among heavy metals, lead, arsenic, mercury, and thallium are the most well-documented culprits. These metals don’t get broken down by the body. Instead, they accumulate and gradually poison nerve fibers. Arsenic poisoning, often from contaminated water, can cause a demyelinating neuropathy severe enough to be mistaken for Guillain-Barré syndrome. About half of people with chronic mercury exposure develop peripheral neuropathy over time, with symptoms including weakness, numbness, and diminished reflexes.
Industrial solvents pose their own risks. Hexane, found in spray cleaners used in the automotive industry, causes symmetrical nerve degeneration. Organophosphates, widely used as pesticides, can trigger neuropathy in acute, intermediate, and delayed forms. Even ethylene oxide, used to sterilize medical equipment, has caused nerve damage in exposed workers. For many of these substances, the neuropathy develops gradually and may not be recognized until significant damage has already occurred.
Inherited Conditions
Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy, linked to mutations in more than 100 different genes. The most frequent subtype, CMT1A, results from a duplicated gene that causes overproduction of a protein involved in building the myelin sheath. Too much of this protein disrupts the insulation around nerves, slowing signal transmission.
Symptoms typically begin in the teen years or early adulthood, starting with weakness in the feet and lower legs. Foot drop, a difficulty lifting the front of the foot, is often one of the first noticeable signs. Over time, the weakness can spread to the hands, making fine motor tasks like buttoning a shirt more difficult. Other features include high arches, hammertoes, balance problems, and lower legs that thin visibly due to muscle wasting. CMT progresses slowly, and most people with the condition remain able to walk throughout their lives, though many benefit from braces or other supportive devices.
Physical Injury and Compression
Nerves can be damaged by direct physical force. Traumatic injuries from accidents, falls, or sports can stretch, crush, or sever peripheral nerves. Compression injuries develop more gradually. Carpal tunnel syndrome, where the median nerve gets pinched at the wrist, is the most familiar example. Similar compression can happen at the elbow (affecting the ulnar nerve), the knee (the peroneal nerve), or anywhere a nerve passes through a tight anatomical space.
Repetitive motions are a common trigger. People whose jobs or hobbies involve sustained gripping, typing, or vibrating tools are at higher risk. Prolonged pressure, such as sitting in one position for hours during surgery or while unconscious, can also compress nerves enough to cause lasting symptoms. In most compression cases, removing the source of pressure allows at least partial recovery, though the timeline depends on how long and how severely the nerve was affected.
When No Cause Is Found
Despite thorough testing, about 30% of peripheral neuropathy cases have no identifiable cause. This is classified as idiopathic neuropathy. It tends to develop gradually, usually after age 60, and most often presents as a slowly progressive sensory neuropathy affecting the feet and lower legs. Some of these cases may involve prediabetes or metabolic changes that don’t yet meet the threshold for a formal diagnosis. Others may reflect genetic variants or subtle toxic exposures that current testing simply can’t detect. Having no identified cause doesn’t change the treatment approach: symptom management and preventing further nerve damage remain the priorities.