Neuropathy is damage to one or more nerves outside the brain and spinal cord, typically causing numbness, tingling, pain, or weakness in the hands and feet. It affects a wide range of people, but diabetes is by far the most common cause, eventually developing in roughly half of all adults with type 1 or type 2 diabetes over their lifetime. The condition can also result from infections, nutritional deficiencies, alcohol use, autoimmune disorders, and dozens of other triggers.
How Your Peripheral Nerves Work
Your body has an enormous network of nerves that branch out from the brain and spinal cord to every other part of the body. These peripheral nerves carry three types of signals. Motor nerves control muscles you move consciously, like those used for walking, gripping, or speaking. Sensory nerves relay information about touch, temperature, and pain. Autonomic nerves handle things you don’t think about: heartbeat, digestion, blood pressure, sweating, and bladder function.
Neuropathy can affect any one of these nerve types or a combination of them. Doctors sometimes describe a case as “predominantly sensory,” “predominantly motor,” “sensory-motor,” or “autonomic” depending on which signals are disrupted. Understanding which type is involved helps explain why symptoms can look so different from one person to the next.
What Damages the Nerves
At the cellular level, nerve damage generally happens in one of two ways. The first is damage to the axon itself, the long fiber that carries electrical signals along the nerve. When an axon is injured, the portion beyond the injury breaks down in a process called Wallerian degeneration. The internal structure of the nerve fiber fragments, and recovery depends on whether the nerve can regrow from the injury site outward.
The second type targets the myelin sheath, an insulating layer that wraps around nerve fibers and speeds up signal transmission. When myelin is stripped away or fails to form properly, nerve signals slow down or become erratic. Some inherited conditions cause defective myelin from birth, while autoimmune diseases can attack healthy myelin later in life. In many real-world cases, both axon damage and myelin damage occur together.
Common Causes
Diabetes dominates the list. The prevalence of neuropathy among adults with diabetes ranges from 6% to 51% depending on age, how long they’ve had diabetes, and how well blood sugar has been controlled. Chronic high blood sugar damages small blood vessels that supply nerves, starving them of oxygen and nutrients over time.
Beyond diabetes, the cause list is long:
- Chronic alcohol use, which is both directly toxic to nerves and often paired with poor nutrition
- Vitamin deficiencies, particularly B1, B6, B12, and vitamin E
- Autoimmune conditions like lupus, rheumatoid arthritis, and Sjögren syndrome
- Infections including shingles, Lyme disease, hepatitis C, and HIV
- Medications, especially certain chemotherapy drugs, some antibiotics, and heart medications
- Toxins such as heavy metals and industrial chemicals
- Inherited conditions, the most common being Charcot-Marie-Tooth disease
- Thyroid problems, particularly an underactive thyroid
Globally, leprosy remains a significant cause of neuropathy, especially in Southeast Asia. And in a substantial number of cases, no cause is ever identified. This is called idiopathic neuropathy.
The most common neuropathy affecting a single nerve is carpal tunnel syndrome, where the median nerve gets compressed at the wrist.
What Neuropathy Feels Like
Sensory neuropathy is the type most people associate with the condition. It typically starts in the feet and works its way upward, a pattern called “length-dependent” because the longest nerves are affected first. Early symptoms include tingling, prickling, or a “pins and needles” sensation. As it progresses, you may feel burning pain, sharp or stabbing sensations, or an unusual sensitivity where even light touch feels painful. In advanced cases, numbness replaces pain entirely, and you lose the ability to feel temperature changes, pressure, or injuries to your skin.
Motor neuropathy shows up as muscle weakness, cramping, or twitching. Over time, muscles can shrink from disuse. In the feet, motor nerve damage distorts the foot’s shape, producing claw toes, high arches, and prominent bones on the sole of the foot that create pressure points.
Autonomic neuropathy is less obvious but can be deeply disruptive. It can cause dizziness or fainting when you stand up due to sudden blood pressure drops. Digestive problems are common: feeling full after just a few bites, nausea, bloating, constipation, or diarrhea. Bladder function may suffer, making it hard to sense when your bladder is full or to empty it completely, which raises the risk of urinary tract infections. Sexual function is often affected too, including erectile dysfunction in men and vaginal dryness or difficulty with arousal in women. Some people find their heart rate no longer adjusts properly during exercise, leaving them unusually winded.
Small Fiber vs. Large Fiber Neuropathy
Not all nerve fibers are the same size, and the distinction matters for both symptoms and diagnosis. Large fibers handle vibration, balance, and proprioception (your sense of where your limbs are in space). When they’re damaged, you may feel unsteady on your feet or have trouble with coordination. Small fibers carry pain, temperature signals, and autonomic functions. Small fiber neuropathy tends to produce burning pain and is strongly associated with autonomic symptoms like abnormal sweating and blood pressure instability.
This distinction also affects how the condition is detected. Standard nerve conduction studies and EMG only test large fibers. If those tests come back normal but you still have classic neuropathy symptoms, small fiber neuropathy is the likely explanation. Confirming it requires a skin biopsy, where a tiny sample of skin is examined under a microscope to count the density of small nerve endings, or specialized autonomic function testing.
How Neuropathy Is Diagnosed
Diagnosis usually starts with a physical exam and a detailed medical history. Your doctor will check reflexes, muscle strength, and your ability to feel sensations like vibration and temperature. Electrodiagnostic testing, which combines nerve conduction studies with needle EMG, is the main tool for confirming neuropathy and determining whether the damage is to the axon, the myelin, or both. During nerve conduction studies, small electrical impulses are sent along a nerve to measure how fast and how strongly the signal travels. EMG involves inserting a thin needle into a muscle to assess the electrical activity there.
Blood work typically follows to look for underlying causes: blood sugar and hemoglobin A1c for diabetes, thyroid function, vitamin levels, markers of autoimmune disease, and sometimes tests for infections. If the electrical tests are normal but symptoms persist, a skin biopsy to evaluate small nerve fiber density can fill in the gap.
Treatment and Management
The most important step in treating neuropathy is addressing whatever is causing it. For diabetic neuropathy, tighter blood sugar control can slow progression and sometimes improve symptoms. For deficiency-related neuropathy, replacing the missing vitamin (most often B12) can lead to significant recovery. Alcohol-related neuropathy requires stopping or drastically reducing alcohol intake alongside nutritional support.
Pain management is often a central concern. Medications commonly used for neuropathic pain work differently from standard painkillers. They target the way nerves transmit pain signals rather than blocking inflammation. These include certain antidepressants and anti-seizure medications, which calm overactive nerve signaling. Topical treatments applied directly to painful areas can help when the discomfort is localized. For some people, combinations of treatments work better than any single approach.
Physical therapy plays a practical role, particularly for motor neuropathy. Strengthening exercises help compensate for weakened muscles, and balance training reduces fall risk. Occupational therapy can help with fine motor tasks if hand function is affected.
Complications Worth Knowing About
The loss of sensation in the feet creates a cascade of problems, especially for people with diabetes. Without the ability to feel pain, small injuries like blisters, cuts, or pressure sores go unnoticed. Autonomic nerve damage compounds this by reducing sweating in the feet, leaving skin dry and prone to cracking. These seemingly minor wounds can develop into deep ulcers that heal slowly and become infected.
Charcot foot is a serious complication where weakened bones in the foot fracture and collapse without the person feeling it happen. The foot becomes red, hot, and swollen, and over time can develop a “rocker-bottom” deformity that makes walking extremely difficult. Catching it early, when warmth and swelling first appear, is critical to preventing permanent damage.
Foot ulcers and the infections that follow remain a leading cause of lower limb amputation in people with diabetes. Daily foot inspections, properly fitting shoes, and regular visits with a foot specialist are practical steps that dramatically reduce this risk. If you have neuropathy in your feet, checking them each night for cuts, redness, or changes in shape is one of the most protective habits you can build.