Neuropathy is diagnosed through a combination of your symptom history, a physical exam, blood tests, and often electrical nerve testing. There’s no single test that confirms it. Instead, doctors work through a process that first confirms nerve damage exists, then identifies the type and underlying cause. The most common form, distal symmetric polyneuropathy, follows a recognizable pattern that typically starts in the toes and feet before reaching the hands.
What Your Doctor Asks First
The diagnostic process starts with a detailed conversation about your symptoms. Your doctor will want to know when symptoms began, how quickly they developed, and exactly where you feel them. These details matter more than you might expect. Neuropathy that develops in under four weeks points to very different causes than neuropathy building over months. Symptoms that appear suddenly within 24 to 72 hours can suggest blood vessel inflammation affecting the nerves, while a slow onset over many weeks or months is more typical of diabetes, nutritional deficiencies, or toxic exposures.
The pattern of your symptoms is equally telling. The most common type of neuropathy affects nerve fibers in a “length-dependent” way, meaning the longest nerves are damaged first. That’s why numbness, tingling, or burning typically starts in the toes and soles of the feet, then gradually moves upward. Hands are usually affected later. If your symptoms follow this stocking-and-glove pattern (affecting the areas covered by socks and gloves), it strongly suggests a systemic cause like diabetes or a vitamin deficiency rather than a problem at one specific nerve site.
Your doctor will also review your medications carefully. Several common drugs can cause neuropathy, including certain chemotherapy agents, seizure medications, some antibiotics, and statins. Alcohol use and exposure to toxins like organophosphates are also important to disclose.
The Physical Exam
A neurological exam tests how well your sensory and motor nerves are functioning. Your doctor will check sensation using a few simple tools. A tuning fork pressed against your toe or ankle tests your ability to feel vibration, which is one of the earliest sensations lost in neuropathy. A pinprick test checks whether you can feel sharp versus dull touch. Temperature sensation may also be tested.
One widely used screening tool is the 10-gram monofilament test, especially for diabetic neuropathy. The doctor presses a thin, flexible nylon filament against points on your foot. If you can’t feel it, that indicates significant sensory loss. This test has a wide range of accuracy depending on how it’s performed: sensitivity ranges from 41% to 93%, and specificity from 68% to 100%. Because of this variability, it’s typically used alongside other tests rather than on its own.
Deep tendon reflexes (like the knee-jerk test) are checked as well. Reduced or absent reflexes at the ankle are a hallmark of peripheral neuropathy. Your doctor will also assess muscle strength in your hands and feet, looking for weakness that suggests motor nerve involvement.
Blood Tests to Identify the Cause
Once nerve damage is suspected, blood work helps pin down why it’s happening. A standard screening panel for neuropathy includes a complete blood count, fasting blood glucose, HbA1c (a measure of blood sugar over the past few months), vitamin B12 levels, thyroid function, kidney and liver function tests, and immunofixation (which detects abnormal proteins in the blood that can signal conditions like certain cancers or immune disorders).
Diabetes and prediabetes are the most common identifiable causes, which is why blood sugar testing is central to the workup. Vitamin B12 deficiency is another frequently found and treatable cause. If B12 levels come back borderline, your doctor may order a follow-up test called methylmalonic acid, which rises when B12 is truly insufficient at the cellular level. These basic labs identify the underlying cause in a significant portion of cases, and the American Academy of Neurology recommends them as part of the standard evaluation for distal symmetric polyneuropathy.
Nerve Conduction Studies and EMG
Electrodiagnostic testing is often the most definitive step in confirming neuropathy and classifying it. This usually involves two tests done in the same visit: nerve conduction studies (NCS) and electromyography (EMG). Together, they take 30 to 60 minutes.
During nerve conduction studies, small electrodes are placed on your skin and mild electrical pulses are sent along specific nerves. The test measures how fast signals travel and how strong they are when they arrive. This distinguishes between the two main types of nerve damage. In demyelinating neuropathy (where the insulating coating around nerves is damaged), signals travel slowly but the nerve fiber itself may be intact. The test shows slowed conduction velocity and prolonged response times. In axonal neuropathy (where the nerve fibers themselves are damaged), signals travel at roughly normal speed but are weaker because fewer fibers are working. The amplitude of the response drops while the speed stays near normal.
EMG involves inserting a thin needle electrode into specific muscles. It records the electrical activity of muscle fibers at rest and during contraction. When nerve fibers have been damaged, the muscles they supply show distinctive patterns of abnormal electrical activity, including small spontaneous discharges called fibrillations. These signals wouldn’t appear in purely demyelinating neuropathy, so EMG helps confirm whether actual nerve fiber loss has occurred. The needle insertion feels like a brief pinch, and while uncomfortable, the test is tolerable for most people.
Autonomic Nerve Testing
If your symptoms include dizziness when standing, abnormal sweating, digestive problems, or changes in heart rate, your doctor may test the autonomic nerves that control these involuntary functions. Several specialized tests exist for this.
A tilt table test evaluates how your blood pressure and heart rate respond to position changes. You lie strapped to a motorized table that gradually tilts you from flat to nearly upright over the course of 45 minutes or more while monitors track your cardiovascular response. If your blood pressure drops significantly or you faint, the table is quickly returned to flat. A second phase using medication to increase heart rate may follow if the first part doesn’t provoke symptoms.
The quantitative sudomotor axon reflex test (QSART) measures sweat gland function. Electrodes placed on your foot, leg, and wrist deliver a mild electrical current along with a chemical that stimulates sweating. A computer analyzes whether the nerves controlling your sweat glands respond normally. Reduced sweating in a specific pattern can confirm small fiber neuropathy, which sometimes doesn’t show up on standard nerve conduction studies.
Deep breathing tests and the Valsalva maneuver (forceful exhaling against resistance) assess how well your autonomic nervous system regulates heart rate. Both are noninvasive and take just a few minutes.
MRI and Nerve Imaging
Standard nerve conduction studies work well for widespread neuropathy, but when the problem is localized (a single trapped or injured nerve, for example), imaging can add crucial detail. Magnetic resonance neurography (MRN) uses specialized MRI sequences to visualize individual nerves directly.
Healthy nerves have a predictable appearance on MRI. Damaged nerves show increased signal on certain sequences, indicating swelling, inflammation, or injury. The scan can pinpoint exactly where along a nerve the damage is, how far it extends, and whether the nerve is being compressed or flattened by surrounding tissue. Nearby muscles also provide clues: when a nerve stops properly supplying a muscle, that muscle shows characteristic signal changes on MRI that confirm denervation.
Contrast dye is sometimes used, particularly when looking for nerve tumors, scar tissue after surgery, or masses pressing on a nerve. Healthy nerves have a protective barrier that prevents contrast from leaking in, so enhancement on imaging signals that the barrier has been disrupted.
When Genetic Testing Is Needed
Most neuropathy is acquired, meaning it develops from diabetes, nutritional deficiencies, immune disorders, or other external causes. But when the evaluation doesn’t reveal a clear cause, or when certain patterns emerge, genetic testing may be recommended.
Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy. If nerve conduction studies show a demyelinating pattern and you have a family history of neuropathy, foot deformities, or slowly progressive weakness, testing for a specific gene duplication (PMP22) is the standard first step. Genetic testing is also recommended when a neuropathy initially thought to be inflammatory doesn’t respond to treatment, since hereditary neuropathies can mimic autoimmune ones.
For rapidly progressive neuropathy of unknown origin, testing for transthyretin amyloidosis is increasingly important. This hereditary condition causes a misfolded protein to accumulate in nerves and organs, and newer treatments can slow its progression significantly if caught early. Identifying it through genetic testing can change the course of the disease.