Neuropathy develops when peripheral nerves are damaged by disease, toxins, physical injury, or genetic conditions. Diabetes is the single most common cause, responsible for nerve damage in up to 50% of people with the disease. But dozens of other triggers exist, from vitamin deficiencies to chemotherapy to long-term alcohol use. In 25% to 46% of cases, no cause is ever identified.
Diabetes and High Blood Sugar
Persistently elevated blood sugar is the leading cause of peripheral neuropathy worldwide. Over time, high glucose triggers a chain of metabolic damage inside nerve fibers: excess sugar gets converted through alternative chemical pathways, toxic byproducts accumulate, and oxidative stress builds up inside the cells. Simultaneously, the tiny blood vessels that supply nerves lose their ability to regulate blood flow properly, starving nerves of oxygen. The nerve endings that control those blood vessels are themselves damaged by diabetes, creating a vicious cycle of worsening blood supply.
This process typically unfolds over years. It most often affects the feet and legs first, producing numbness, tingling, or burning pain that gradually moves upward. Roughly one in three people with diabetes develops painful neuropathy, and the risk climbs the longer blood sugar remains poorly controlled.
Chemotherapy
Certain cancer drugs are directly toxic to peripheral nerves. The classes most likely to cause neuropathy include platinum-based drugs (commonly used for colon and ovarian cancers), taxanes (used for breast and lung cancers), vinca alkaloids (used in lymphomas and leukemias), and some drugs used to treat multiple myeloma. The risk increases with higher doses, more treatment cycles, and combination regimens that stack multiple nerve-damaging agents.
Chemotherapy-induced neuropathy typically starts in the fingertips and toes as numbness or tingling, sometimes with sharp or burning pain. For some people it resolves after treatment ends, but for others it becomes a chronic problem that persists for months or years.
Alcohol and Nutritional Deficiencies
Heavy, long-term alcohol use is a well-established cause of neuropathy. Research links it most clearly to people consuming more than 100 grams of alcohol per day (roughly seven standard drinks) for more than 10 years, though the total lifetime amount matters as well. Alcohol damages nerves both through direct toxicity and by depleting essential nutrients, particularly B vitamins, that nerves need to function.
Vitamin B12 deficiency on its own can cause neuropathy even without alcohol involvement. People with low B12 levels show measurably reduced nerve conduction speed and greater loss of sensitivity to light touch compared to those with normal levels. B12 deficiency is especially common in older adults, people taking certain acid-reducing medications, and those with digestive conditions that impair nutrient absorption. Other nutritional gaps that can damage nerves include deficiencies in vitamins B1, B6, and E, as well as copper.
Infections
Several infections can damage peripheral nerves directly or trigger an immune response that attacks them. HIV can cause neuropathy both from the virus itself and from the medications used to treat it. Lyme disease, caused by the bacterium transmitted through tick bites, can produce nerve pain and weakness when the infection spreads beyond the initial skin rash. Shingles, a reactivation of the chickenpox virus, is one of the more common infectious causes. The virus lives dormant in nerve cells and, when it flares, can leave behind lingering nerve pain called postherpetic neuralgia that sometimes lasts months or years after the rash heals.
Physical Compression and Injury
Nerves can be damaged when they’re compressed, stretched, or cut. Carpal tunnel syndrome is the most common example, accounting for 90% of all focal neuropathy cases. It occurs when the median nerve gets squeezed as it passes through a narrow channel in the wrist, causing pain, numbness, and tingling in the thumb, index, middle, and half of the ring finger.
Other common compression sites include the elbow (where the ulnar nerve can be pinched, causing numbness in the pinky and ring finger) and the outside of the knee (where the peroneal nerve can be compressed, leading to foot drop). Repetitive motions, prolonged pressure from crutches or casts, herniated discs, and traumatic injuries like fractures can all damage nerves at specific points along their path.
Toxic Exposures and Heavy Metals
Certain metals are toxic to nerves even at relatively low concentrations. Lead, arsenic, mercury, and thallium are the most recognized culprits, and each produces a somewhat distinct pattern of damage.
- Lead poisoning classically causes weakness in the muscles that extend the wrist and foot (leading to wrist drop or foot drop), along with milder sensory symptoms. Occupational exposure and contaminated water are the most common sources. Neurological damage from lead can persist even after other symptoms improve.
- Arsenic exposure, most often from contaminated water or food, causes numbness and tingling in chronic cases. At higher doses it can trigger a rapidly progressing neuropathy that mimics Guillain-Barré syndrome.
- Mercury accumulates from industrial exposure, contaminated fish, and other sources. About half of people with chronic mercury exposure eventually develop neuropathy with weakness, numbness, and reduced reflexes.
- Thallium, found in some pesticides, can cause neuropathy along with hair loss and mental disturbances. It too can be mistaken for Guillain-Barré syndrome.
Industrial solvents, certain pesticides, and even colloidal silver (sometimes taken as an unproven supplement) have also been linked to nerve damage in rare cases.
Inherited Neuropathy
Some people are born with genetic mutations that cause their nerves to deteriorate over time. The most common inherited form is Charcot-Marie-Tooth disease, which affects roughly 1 in 2,500 people. Mutations in at least 17 different genes have been identified as causes, with a single gene duplication (PMP22) responsible for about 50% of all cases and at least 70% of the most common subtype.
Symptoms usually begin in childhood or the teenage years, though some forms appear later. They typically start with weakness and numbness in the feet and lower legs, gradually progressing to the hands. The pace varies widely depending on which gene is affected. Some forms primarily damage the insulating coating around nerves, slowing signal transmission. Others damage the nerve fiber itself. A few gene mutations can cause either pattern.
Autoimmune and Inflammatory Conditions
The immune system can mistakenly attack peripheral nerves. In Guillain-Barré syndrome, this happens acutely, often after an infection, and can cause rapid-onset weakness. Chronic inflammatory demyelinating polyneuropathy (CIDP) is a longer-term version where the immune system gradually strips the insulating layer off nerves. Lupus, rheumatoid arthritis, and Sjögren’s syndrome can all include neuropathy as a complication, driven by inflammation of the small blood vessels that feed nerves.
When No Cause Is Found
Despite thorough testing, doctors cannot identify a cause in a substantial number of cases. Studies estimate that 25% to 46% of peripheral neuropathy cases are classified as idiopathic, meaning the cause remains unknown. This is more common in older adults. The standard workup includes blood tests for blood sugar levels, kidney and liver function, thyroid hormones, B12 levels, and certain protein abnormalities. If those come back normal, a neurologist may order nerve conduction studies, specialized antibody tests, or in rare cases a nerve biopsy to look for less common causes. Even with this full evaluation, many cases remain unexplained.