Diabetic peripheral and autonomic neuropathy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Diabetic peripheral neuropathy is a diagnosis of pattern and exclusion. The commonest phenotype is a chronic, symmetrical, length-dependent polyneuropathy: small-fibre dysfunction produces burning pain, allodynia and altered temperature sensation, while large-fibre injury impairs vibration, proprioception and ankle reflexes. Loss of protective sensation allows repetitive pressure, ill-fitting footwear and heat injury to progress without pain. Neuropathic pain and insensate feet can coexist; asking only whether the feet hurt misses those at greatest ulcer risk.

Atypical features should interrupt the diabetic label. Marked asymmetry, motor predominance, upper-limb onset, sensory level, sphincter dysfunction, rapid progression or prominent systemic illness suggests entrapment, radiculopathy, vasculitis, inflammatory neuropathy, spinal disease or another neurological disorder. Review diabetes duration and trajectory, alcohol, nutrition, renal function and neurotoxic medicines. Metformin use, macrocytosis or dietary risk raises vitamin B12 deficiency, but normal blood count does not exclude it. Nerve-conduction studies assess large fibres and are reserved for atypical, progressive or diagnostically uncertain presentations; they can be normal in isolated small-fibre disease.

Autonomic neuropathy is organ-specific rather than a single screening-test result. Cardiovascular autonomic failure causes resting tachycardia, postural hypotension and exercise intolerance; gastroparesis creates early satiety, vomiting and erratic insulin–carbohydrate matching; enteropathy can cause nocturnal diarrhoea or constipation; bladder dysfunction causes retention or recurrent infection; sudomotor failure produces dry cracked feet; erectile and other sexual dysfunction affect wellbeing. Diagnose after excluding medicine effects, dehydration, endocrine disease and mechanical causes. Management combines risk-factor control, symptom-directed specialty care, foot protection and review of treatment harm.

Key points

Distal symmetrical sensorimotor polyneuropathy usually begins in the toes with length-dependent numbness, burning, electric pain or loss of protective sensation.
A 10 g monofilament identifies loss of protective sensation but does not exclude small-fibre painful neuropathy when the result is normal.
Check pulses, skin, footwear, deformity, callus and previous ulcer at every formal foot assessment because neuropathy converts pressure into unnoticed injury.
Diabetes is common but not exclusive: consider vitamin B12 deficiency, alcohol, CKD, thyroid disease, medicines, paraproteinaemia, entrapment and inflammatory neuropathy.
Autonomic involvement can affect blood pressure, heart rate, sweating, stomach emptying, bowel habit, bladder, sexual function and awareness of hypoglycaemia.
Optimise glucose safely and address smoking, alcohol, blood pressure, lipids and nutrition; overly rapid glycaemic improvement can occasionally provoke acute painful neuropathy.
NICE offers amitriptyline, duloxetine, gabapentin or pregabalin as initial non-specialist options for neuropathic pain, selected by comorbidity and patient preference.
Review analgesic benefit by pain, sleep and function, and plan deprescribing; gabapentinoids carry dependence, withdrawal, sedation and respiratory-depression risks.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Chronic hyperglycaemic injury

Prolonged metabolic exposure damages small and large peripheral nerve fibres, with risk shaped by diabetes duration and glycaemic trajectory.

Vascular and systemic contributors

Smoking, kidney disease, alcohol, nutritional deficiency and vascular risk can compound diabetic nerve injury or produce a clinically similar neuropathy.

Medicine and nutritional effects

Metformin-associated vitamin B12 deficiency and neurotoxic medicines are treatable contributors that should not be hidden beneath the diabetes label.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Distal sensory fibres fail
Length-dependent small-fibre damage causes burning, allodynia and altered temperature sensation, while large-fibre injury reduces vibration and proprioception.
2
Protective sensation is lost
Insensate feet continue to bear pressure and sustain heat or footwear injury without warning pain, allowing ulcers to develop unnoticed.
3
Autonomic fibres become dysfunctional
Damage to cardiovascular, gastrointestinal, genitourinary and sudomotor pathways disrupts postural responses, motility, bladder function, sexual function and skin integrity.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Length-dependent sensory change

Numbness, tingling, burning or shooting discomfort starts in toes and advances in a stocking distribution. Hand symptoms usually arise only after lower-limb involvement is established.

Loss of protective sensation

A patient may report painless burns, stones in shoes or unrecognised blisters. Monofilament loss identifies ulcer vulnerability and requires foot-protection referral by risk category.

Painful small-fibre disease

Burning, stabbing, electric pain and allodynia can be worse at night despite preserved strength, reflexes and monofilament sensation. Validate pain while excluding mimics.

Atypical neurological patternRed flag

Rapid evolution, pronounced weakness, asymmetry, a sensory level, cranial signs or sphincter change requires urgent neurological reassessment rather than routine diabetes follow-up.

Postural autonomic symptoms

Light-headedness, visual dimming, neck discomfort or syncope on standing may reflect autonomic hypotension, but bleeding, dehydration, antihypertensives, arrhythmia and adrenal disease remain alternatives.

Gastrointestinal dysautonomia

Early satiety, vomiting of undigested food, unpredictable post-meal glucose, nocturnal diarrhoea or severe constipation warrants evaluation for medicines, obstruction, coeliac disease and infection before attribution.

Genitourinary involvement

Erectile dysfunction, reduced arousal, incomplete bladder emptying, overflow, recurrent urinary infection or incontinence may indicate autonomic damage but need urological and medicine review.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Structured neurological foot examinationFirst step
Why
Define distribution, protective sensation, motor involvement and immediate ulcer risk.
Interpretation and limitations
Test 10 g monofilament at recommended sites alongside vibration or pinprick, reflexes, strength, skin and footwear. An insensate site changes foot-risk status; a normal monofilament does not exclude painful small-fibre neuropathy.
02
Peripheral vascular and skin assessment
Why
Identify ischaemia, pressure points and tissue injury that compound neuropathic risk.
Interpretation and limitations
Palpate pulses and inspect temperature, colour, callus, deformity, fissures, nail disease and between toes. Absent pulses or tissue loss needs vascular and diabetic-foot pathways rather than analgesia alone.
03
FBC, vitamin B12, renal profile and TSH
Why
Find common reversible or contributory metabolic causes of neuropathy.
Interpretation and limitations
Interpret B12 with symptoms, metformin exposure and laboratory caveats; CKD and thyroid disease can contribute. Broader tests such as folate, electrophoresis or autoimmune studies follow the phenotype.
04
Nerve-conduction studies and EMG
Why
Characterise large-fibre, demyelinating, axonal, focal or motor neuropathy when the pattern is atypical.
Interpretation and limitations
Typical slowly progressive distal symmetrical neuropathy may not require testing. Normal studies do not rule out small-fibre disease, while demyelination or focal conduction block changes referral urgency.
05
Lying and standing blood pressure with pulse
Why
Document reproducible orthostatic haemodynamic change and relate it to symptoms.
Interpretation and limitations
Repeat after adequate supine rest and review fluids and medicines. A postural fall supports orthostatic hypotension but does not prove diabetic autonomic causation.
06
ECG and cardiovascular assessment
Why
Exclude rhythm, conduction or ischaemic causes of syncope and exercise intolerance.
Interpretation and limitations
Resting tachycardia or reduced variability may support autonomic dysfunction, but ECG abnormalities, exertional chest equivalents or structural signs require the appropriate cardiac pathway.
07
Gastric or urological specialist testing
Why
Confirm organ dysfunction after mechanical and medicine causes are excluded.
Interpretation and limitations
Upper endoscopy or imaging may precede gastric-emptying assessment; post-void bladder volume and urodynamics are selective. Test choice follows the symptom and specialist question.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Vitamin B12 deficiency

Dietary risk, metformin use, macrocytosis or posterior-column features support deficiency, but a normal blood count does not reliably exclude it.

Entrapment or radiculopathy

Focal distribution, dermatomal pain or unilateral weakness suggests nerve compression or root disease rather than symmetrical length-dependent diabetic neuropathy.

Inflammatory or vasculitic neuropathy

Rapid progression, marked asymmetry, motor predominance or systemic inflammatory features should prompt urgent neurological assessment for another process.

Spinal cord disease

A sensory level, upper motor-neurone signs or sphincter dysfunction is incompatible with routine distal neuropathy and requires spinal evaluation.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ScreenFind neuropathy and foot riskFirst stepA person attends annual diabetes review or reports sensory symptoms, pain, balance change or unnoticed injury.

1Ask about pain, numbness, balance, falls, skin injury and footwear, then inspect both feet, palpate pulses and test protective sensation using the local NICE-aligned technique.
2Classify foot risk from neuropathy, vascular supply, deformity, callus, previous ulcer or amputation and renal replacement therapy, and arrange the required foot-protection follow-up.
3Give specific daily inspection, footwear and temperature-injury advice, with a same-day route for a new blister, colour change, swelling, break in skin or discharge.

02DifferentiateChallenge the diabetic attributionNeuropathy is new, painful, progressive or not a classic symmetrical distal pattern.

1Map sensory and motor findings, reflexes and tempo, looking explicitly for asymmetry, proximal weakness, upper motor-neurone signs, sensory level, systemic illness and sphincter dysfunction.
2Review alcohol, nutrition, metformin, chemotherapy and other neurotoxic exposure, and test common reversible metabolic causes before deciding the presentation is diabetic.
3Refer urgently for rapidly progressive weakness or central signs, and request neurology or neurophysiology input for atypical, function-limiting or diagnostically uncertain disease.

03RelieveTreat pain and autonomic dysfunctionNeuropathic pain impairs sleep or function, or an autonomic symptom has been confirmed after competing causes are reviewed.

1Agree functional goals and select one NICE initial neuropathic-pain medicine using renal, hepatic, cardiac, mental-health, falls, driving and dependence considerations; titrate and review one change at a time.
2If ineffective or intolerable, switch among recommended options rather than layering sedatives indefinitely; consider capsaicin cream for selected localised pain and refer severe refractory pain.
3For autonomic disease, correct contributing medicines and dehydration, use organ-specific measures and involve gastroenterology, urology, cardiology or sexual-health services when symptoms persist or red flags arise.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

One NICE initial option for neuropathic pain, particularly when a serotonin–noradrenaline reuptake inhibitor fits comorbidity and patient preference.

Duloxetine

For licensed diabetic peripheral neuropathic pain, the starting and recommended maintenance dose is 60 mg once daily with or without food; review response after two months and follow the exact current product information.

Avoid in hepatic impairment causing liver dysfunction, severe renal impairment and uncontrolled hypertension as specified by the SmPC. Review serotonergic interactions, bleeding risk, hyponatraemia, suicidality and withdrawal; taper rather than stopping suddenly.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Foot ulceration and amputation

Loss of sensation and dry skin permit repeated unnoticed injury, which can progress to infection, osteomyelitis and limb loss.

Falls and functional decline

Impaired proprioception, weakness and postural hypotension destabilise gait, limiting activity and increasing falls and fracture risk.

Organ-specific autonomic failure

Gastroparesis, bladder retention, erectile dysfunction and cardiovascular autonomic failure can impair nutrition, infection control, treatment matching and quality of life.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Repeat formal foot-risk assessment at least annually and more often through the foot-protection service when neuropathy, deformity, PAD or previous ulcer raises risk.
At each pain-treatment review, record pain intensity, sleep, walking and daily function as well as dizziness, sedation, falls, mood and medicine adherence.
Check renal and hepatic function where it changes analgesic selection or dose, and reassess gabapentinoid dependence, respiratory and withdrawal risk before repeats.
Monitor postural symptoms, lying and standing blood pressure, falls and interacting hypotensive medicines after any autonomic treatment change.
For suspected gastroparesis, track weight, hydration, nutrition, vomiting, ketones and mismatch between insulin action and carbohydrate absorption with diabetes-team input.
Escalate any new skin break, hot swollen foot, blackening, discharge or rest pain immediately rather than waiting for a scheduled neuropathy appointment.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Pain does not protect

A painful foot can still have enough sensory loss to miss trauma, so a symptom label never replaces monofilament, vascular and skin assessment.

Small fibres hide

Routine nerve-conduction studies examine large myelinated fibres and may be normal when burning pain and temperature disturbance arise predominantly from small fibres.

Autonomic is plural

Cardiovascular, gastric, bowel, bladder, sudomotor and sexual dysfunction need separate confirmation and treatment; one symptom does not prove global autonomic failure.

Glycaemic pace matters

Long-term glucose optimisation reduces progression risk, but unusually rapid improvement can be followed by an acute painful neuropathy that merits specialist recognition rather than treatment abandonment.

Medicine burden can mimic

Sedatives worsen balance, antihypertensives worsen postural symptoms and GLP-1 receptor agonists can delay gastric emptying, so medication chronology is part of neuropathy diagnosis.

11Common pitfallsFrequent interpretation and management errors.

01
Calling every numb or painful foot diabetic neuropathy without checking pulses, skin, footwear and focal neurological alternatives.
02
Using a normal 10 g monofilament result to exclude small-fibre neuropathic pain.
03
Missing vitamin B12 deficiency in a metformin-treated person because the mean cell volume is normal.
04
Escalating several sedating neuropathic-pain medicines without measurable functional benefit or a deprescribing plan.
05
Attributing syncope to autonomic neuropathy before excluding bleeding, dehydration, arrhythmia and medicine effects.
06
Treating vomiting as gastroparesis without checking ketones, obstruction, pregnancy, medicines and acute metabolic illness.