Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 14 peer-reviewed journal articles Updated
Neurology

Testing and Tools: How Your Nerves Are Measured

At a Glance

Diabetic polyneuropathy is diagnosed using physical exams and advanced nerve tests. A standard yearly check includes monofilament, tuning fork, and pinprick tests to measure nerve sensation in the feet. Tools like Nerve Conduction Velocity can even detect damage before you feel symptoms.

Diagnosing diabetic polyneuropathy is not a single event but a process of gathering objective data about how well your nerves are functioning. The American Diabetes Association (ADA) recommends that every person with diabetes undergo a comprehensive foot and neurological exam at least once a year—and more frequently if you already have risk factors like numbness or prior foot ulcers [1][2].

The Bedside Exam: Three Key Tools

During a standard clinical exam, your doctor uses simple tools to test different types of nerve fibers. Each of these tests provides a piece of the puzzle:

  • 10-g Semmes-Weinstein Monofilament: This is a small, flexible plastic wire used to touch specific spots on your feet. It measures your pressure threshold. If you cannot feel the 10-gram force of the wire, you have what is called Loss of Protective Sensation (LOPS), which is the most significant predictor of future foot ulcers [3][4].
  • 128-Hz Tuning Fork: The doctor strikes the fork and places the base against the bony parts of your big toe or ankle. This tests your vibration perception, which is a measure of how well your large-diameter nerve fibers are working [5].
  • Pinprick Test: By gently touching the skin with a sharp object (like a specialized neuro-pin), the doctor assesses your small-fiber function. These small fibers are responsible for carrying pain and temperature signals [6].

Advanced Diagnostic Tools

If your bedside exam is unclear or if your doctor needs to assess the severity of damage, they may use advanced technology:

  • Nerve Conduction Velocity (NCV): Often considered a “gold standard,” this test uses small electrical pulses to measure how fast and how strong signals travel through your nerves [7]. It is excellent for detecting large-fiber damage even before you feel symptoms [8].
  • Sudoscan: This is a quick, non-invasive test where you place your hands and feet on stainless-steel plates. It measures sudomotor function (how well your sweat glands react to a small electrical stimulus). Since sweat glands are controlled by the autonomic nervous system, this is a highly sensitive way to catch early small-fiber damage [9][10].
  • Corneal Confocal Microscopy (CCM): This is a rapid eye scan that takes high-resolution images of the nerves in your cornea. Because these nerves are similar to the ones in your feet, CCM can identify nerve fiber loss throughout the body without needing a skin biopsy [11][12].

Completeness Checklist

A thorough neurological and foot exam should never be rushed. Ensure your doctor covers these six essential areas:

  1. Visual Inspection: Checking for dry skin, calluses, fungal infections, and changes in the shape of the foot.
  2. Pulse Check: Feeling the pulses on the top and side of the foot to ensure good blood flow [1].
  3. Monofilament Testing: Testing at least 4 to 10 specific sites on each foot [13].
  4. Vibration Testing: Using a 128-Hz tuning fork.
  5. Reflexes: Testing the “ankle jerk” (Achilles reflex).
  6. Gait and Balance: Observing how you walk to see if nerve damage is affecting your stability [14].

Common questions in this guide

What is the monofilament test for diabetic neuropathy?
The 10-g Semmes-Weinstein monofilament test uses a flexible plastic wire to touch specific spots on your feet. It measures whether you have lost protective sensation, which is a major predictor for developing future foot ulcers.
Why does my doctor use a tuning fork on my feet?
A 128-Hz tuning fork is used to test your vibration perception. When placed against the bony parts of your toe or ankle, it helps the doctor measure how well your large-diameter nerve fibers are functioning.
What is a nerve conduction velocity (NCV) test?
An NCV test is a diagnostic tool that uses small electrical pulses to measure how quickly and strongly signals travel through your nerves. It is considered a highly reliable way to detect large-fiber nerve damage before you even feel symptoms.
How does a Sudoscan check for diabetic nerve damage?
A Sudoscan is a quick, non-invasive test that measures how well your sweat glands react to a small electrical stimulus. Because sweat glands are controlled by the autonomic nervous system, this test helps spot early damage to small nerve fibers.
What should be included in a complete diabetic foot exam?
A thorough exam should include a visual check for skin issues or shape changes, a pulse check for blood flow, and tests for sensation, vibration, reflexes, and balance. You should have this comprehensive check at least once a year.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Can you perform a 10-g monofilament test and a 128-Hz tuning fork test today to check for loss of protective sensation?
  2. 2.Are the pulses in my feet strong enough to ensure healthy blood flow for healing?
  3. 3.Based on my symptoms, should I have a 'gold standard' Nerve Conduction Velocity (NCV) test to check for subclinical nerve damage?
  4. 4.Would a Sudoscan or corneal confocal microscopy be helpful for detecting early small-fiber damage?
  5. 5.How often should I have this comprehensive exam given my current symptoms and risk factors?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (14)
  1. 1

    The Diabetic Foot Assessment.

    Johnson R, Osbourne A, Rispoli J, Verdin C

    Orthopedic nursing 2018; (37(1)):13-21 doi:10.1097/NOR.0000000000000414.

    PMID: 29369130
  2. 2

    Association of Preulcerative Foot Care and Outcomes of Diabetic Foot Ulceration.

    Tan TW, Tolson JP, Aristizabal JCA, et al.

    Journal of the American Podiatric Medical Association 2024; (114(2)).

    PMID: 38758687
  3. 3

    Studying the Diabetic Foot at Risk Using a 60-Second Foot Screening Tool and the Importance of the Categories of the Foot at Risk in Diabetes Patients at a Tertiary Care Center in East India.

    Behera KK, Soren UK, Behera BK, Devi S

    Cureus 2024; (16(10)):e72615 doi:10.7759/cureus.72615.

    PMID: 39610618
  4. 4

    Wherefore Art Thou, O Treatment for Diabetic Neuropathy?

    Malik RA

    International review of neurobiology 2016; (127()):287-317.

    PMID: 27133154
  5. 5

    [Sudomotor dysfunction diagnostic test for early detection of diabetic neuropathy].

    Lorenzini N, Díaz C, Quintana T

    Revista medica de Chile 2020; (148(1)):54-59 doi:10.4067/S0034-98872020000100054.

    PMID: 32730436
  6. 6

    Corneal confocal microscopy detects small nerve fibre damage in patients with painful diabetic neuropathy.

    Kalteniece A, Ferdousi M, Azmi S, et al.

    Scientific reports 2020; (10(1)):3371 doi:10.1038/s41598-020-60422-7.

    PMID: 32099076
  7. 7

    High Prevalence and Incidence of Diabetic Peripheral Neuropathy in Children and Adolescents With Type 1 Diabetes Mellitus: Results From a Five-Year Prospective Cohort Study.

    Walter-Höliner I, Barbarini DS, Lütschg J, et al.

    Pediatric neurology 2018; (80()):51-60 doi:10.1016/j.pediatrneurol.2017.11.017.

    PMID: 29429781
  8. 8

    Nerve conduction studies in diabetics presymptomatic and symptomatic for diabetic polyneuropathy.

    de Souza RJ, de Souza A, Nagvekar MD

    Journal of diabetes and its complications 2015; (29(6)):811-7.

    PMID: 26049172
  9. 9

    Comparison of electrochemical skin conductance and vibration perception threshold measurement in the detection of early diabetic neuropathy.

    Goel A, Shivaprasad C, Kolly A, et al.

    PloS one 2017; (12(9)):e0183973 doi:10.1371/journal.pone.0183973.

    PMID: 28880907
  10. 10

    Rapid, Objective and Non-invasive Diagnosis of Sudomotor Dysfunction in Patients With Lower Extremity Dysesthesia: A Cross-Sectional Study.

    Chae CS, Park GY, Choi YM, et al.

    Annals of rehabilitation medicine 2017; (41(6)):1028-1038 doi:10.5535/arm.2017.41.6.1028.

    PMID: 29354580
  11. 11

    Corneal confocal microscopy compared with quantitative sensory testing and nerve conduction for diagnosing and stratifying the severity of diabetic peripheral neuropathy.

    Ferdousi M, Kalteniece A, Azmi S, et al.

    BMJ open diabetes research & care 2020; (8(2)) doi:10.1136/bmjdrc-2020-001801.

    PMID: 33355206
  12. 12

    Quantitative analysis of corneal nerve fibers in type 2 diabetics with and without diabetic peripheral neuropathy: Comparison of manual and automated assessments.

    Li Q, Zhong Y, Zhang T, et al.

    Diabetes research and clinical practice 2019; (151()):33-38 doi:10.1016/j.diabres.2019.03.039.

    PMID: 30935930
  13. 13

    Easier operation and similar power of 10 g monofilament test for screening diabetic peripheral neuropathy.

    Zhang Q, Yi N, Liu S, et al.

    The Journal of international medical research 2018; (46(8)):3278-3284 doi:10.1177/0300060518775244.

    PMID: 29808737
  14. 14

    Postural sway serves as a predictive biomarker in balance and gait assessments for diabetic peripheral neuropathy screening: a community-based study.

    Lai YR, Chiu WC, Ting CP, et al.

    Journal of neuroengineering and rehabilitation 2025; (22(1)):123 doi:10.1186/s12984-025-01644-6.

    PMID: 40452056

This page is for educational purposes only and does not replace professional medical advice. Always consult your healthcare provider or podiatrist for comprehensive diabetic foot and neurological exams.

Get notified when new evidence is published on diabetic polyneuropathy.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.