What is ICD-10 code G61.9?

G61.9 is the ICD-10-CM diagnosis code for Inflammatory polyneuropathy, unspecified. Inflammation affecting multiple nerves throughout the body where the specific cause or type cannot be determined. It belongs to the ICD-10-CM chapter for diseases of the nervous system (g00-g99). G61.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G61.9 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G61.9 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G61.9 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for G61.9?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. G61.9 was a payment HCC under V24 (Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting G61.9?

This is an unspecified code; query the provider for more specific diagnostic information before coding Review all available test results and clinical findings to determine if a more specific G61 code applies Because G61.9 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

G61.9: Inflammatory polyneuropathy, unspecified — ICD-10 | Myasthenia Gravis/Myoneural Disorders

ICD-10-CM Code View

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Code lookupG61.9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Polyneuropathies and other disorders of the peripheral nervous system (G60-G65)

G61.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Inflammatory polyneuropathy, unspecified

Inflammation affecting multiple nerves throughout the body where the specific cause or type cannot be determined.

Buddy Insight

Inflammatory polyneuropathy, unspecified represents an inflammatory nerve condition where the specific type cannot be determined.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Mapped

HCC 75

Myasthenia Gravis/Myoneural D...

RAF 0.472

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 75

Myasthenia Gravis/Myoneural D...

RAF 0.0

RXHCC

Mapped

HCC 158

Guillain-Barre Syndrome and O...

RAF 0.0

Code Trumping

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Code Book Path

Official

G61Inflammatory polyneuropathy

G61.9Inflammatory polyneuropathy, unspecified

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for G61.9 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G61.9 in this effective period.

Related Child Codes

Official

G61.0Guillain-Barre syndrome

G61.1Serum neuropathy

G61.8Other inflammatory polyneuropathies

Includes

Official

ICD-10-CM does not list Includes notes for G61.9 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for G61.9 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G61.9 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G61.9 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G61.9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Evidence of polyneuropathy: clinical symptoms of weakness, sensory changes, or pain in multiple nerve distributions

Laboratory or electrodiagnostic evidence of inflammatory etiology

Documentation explaining why a more specific type cannot be determined

Treatment plan addressing the inflammatory polyneuropathy

MEAT Support

HCC Buddy guidance

Evidence of polyneuropathy: clinical symptoms of weakness, sensory changes, or pain in multiple nerve distributions

Laboratory or electrodiagnostic evidence of inflammatory etiology

Documentation explaining why a more specific type cannot be determined

Treatment plan addressing the inflammatory polyneuropathy

Audit Caution

HCC Buddy guidance

Using this unspecified code when sufficient documentation exists to assign a more specific G61 code

Not querying the provider to obtain the specific type of inflammatory polyneuropathy

Accepting this code at face value without reviewing nerve conduction studies or specialist notes that may provide specificity

Confusing with G62.9 which does not specify the inflammatory nature of the condition

Common Mistakes

HCC Buddy guidance

G61.0 — Guillain-Barre syndrome should be used when acute ascending paralysis is documented with diagnostic confirmation

G61.81 — CIDP should be used for chronic demyelinating polyneuropathy lasting beyond 8 weeks

G61.89 — Other inflammatory polyneuropathies is preferred when the provider specifies a type but it does not have its own code

G62.9 — Polyneuropathy, unspecified is even more general and does not specify inflammatory etiology

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is G61.9 an HCC code?

Yes. G61.9 maps to Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy under the V24 model but is not retained in V28.

HCC Category Mapping

V24HCC 75, Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy

0.472

ESRDHCC 75, Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy

0.000

RxHCCHCC 158, Guillain-Barre Syndrome and Other Polyneuropathies

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work G61.9 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for G61.9

For G61.9to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G61.9 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

G61.9 is the ICD-10-CM diagnosis code for inflammatory polyneuropathy, unspecified. Inflammation affecting multiple nerves throughout the body where the specific cause or type cannot be determined. G61.9 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering polyneuropathies and other disorders of the peripheral nervous system (g60-g65).

Under the older CMS-HCC V24 model, G61.9 maps to Myasthenia Gravis/Myoneural Disorders and Guillain-Barre Syndrome/Inflammatory and Toxic Neuropathy (HCC 75) with a community, non-dual, aged base RAF weight of 0.472. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This is an unspecified code; query the provider for more specific diagnostic information before coding. Because G61.9 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G61.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is an unspecified code; query the provider for more specific diagnostic information before coding
•Review all available test results and clinical findings to determine if a more specific G61 code applies

Clinical Significance

Inflammatory polyneuropathy, unspecified represents an inflammatory nerve condition where the specific type cannot be determined. While this captures disease complexity for risk adjustment, it is a non-specific code that ideally should be replaced with a more precise diagnosis. It still reflects a patient with significant neurological disease burden requiring treatment.

Documentation Requirements

✓Evidence of polyneuropathy: clinical symptoms of weakness, sensory changes, or pain in multiple nerve distributions
✓Laboratory or electrodiagnostic evidence of inflammatory etiology
✓Documentation explaining why a more specific type cannot be determined
✓Treatment plan addressing the inflammatory polyneuropathy
✓Follow-up plan for additional diagnostic workup to refine the diagnosis
✓Provider's clear diagnosis of inflammatory polyneuropathy

Commonly Confused Codes

•G61.0: Guillain-Barre syndrome should be used when acute ascending paralysis is documented with diagnostic confirmation
•G61.81: CIDP should be used for chronic demyelinating polyneuropathy lasting beyond 8 weeks
•G61.89: Other inflammatory polyneuropathies is preferred when the provider specifies a type but it does not have its own code
•G62.9: Polyneuropathy, unspecified is even more general and does not specify inflammatory etiology