Question 1

What is ICD-10 code G59?

Accepted Answer

G59 is the ICD-10-CM diagnosis code for mononeuropathy in diseases classified elsewhere. Damage to a single nerve that occurs as a result of another disease or condition the patient has. G59 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering nerve, nerve root and plexus disorders (g50-g59).

G59 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

This code requires documentation of the underlying disease; code the primary condition first, then G59.

Question 2

Is G59 an HCC code?

Accepted Answer

No. G59 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is G59 billable?

Accepted Answer

Yes. G59 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. G59 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.

Question 4

What is the V28 vs V24 difference for G59?

Accepted Answer

G59 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards G59 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting G59?

Accepted Answer

This code requires documentation of the underlying disease; code the primary condition first, then G59 Common causes include diabetes, infections, and malignancies; ensure the causal relationship is documented

HCC Buddy Code Card

G59

Is G59 an HCC code?

What This Code Means

Coding Tips

Excludes 1, Do NOT code together

Code First

Code Hierarchy

Work G59 in HCC Buddy

G59 ICD-10-CM Code: Mononeuropathy in diseases classified elsewhere

HCC Buddy Code Card

G59

Is G59 an HCC code?

What This Code Means

Coding Tips

Excludes 1, Do NOT code together

Code First

Code Hierarchy

Work G59 in HCC Buddy