ICD-10 G20.C
Billable / Specific HCC v28: 78Parkinsonism, unspecified
About ICD-10-CM G20.C
ICD-10-CM code G20.C represents Parkinsonism, unspecified. This is a billable/specific code in the Nervous System chapter (block G20). The 2026 edition of ICD-10-CM G20.C became effective on October 1, 2025.
Coding Tips for G20.C
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G20.C is a CMS-HCC v28 risk-adjustment code (category 78). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under G20.C. Per CMS ICD-10-CM Tabular 2026.
- Parkinsonism, NOS
Type 1 Excludes
Pure excludes, these codes can never be coded together with G20.C. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- Parkinson's disease NOS (G20.A1)
- Parkinson's disease with dyskinesia (G20.B-)
- Parkinson's disease without dyskinesia (G20.A-)
- secondary parkinsonism (G21.-)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for G20.C
Local Coverage Determinations (LCDs) from CMS MACs that list G20.C as a covered diagnosis.
Showing top 10 of 339 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G20.C.
1 Aetna
2 Cigna
5 Medicare
CPT Codes Commonly Billed with G20.C
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 95923 CMS LCD: Billing and Coding: Autonomic Function Testing CMS LCD
- 95924 CMS LCD: Billing and Coding: Autonomic Function Testing CMS LCD
- 95921 CMS LCD: Billing and Coding: Autonomic Function Testing CMS LCD
- 95922 CMS LCD: Billing and Coding: Autonomic Function Testing CMS LCD
- 51741 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51728 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51729 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 55899 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51792 CMS LCD: Billing and Coding: Urodynamics CMS LCD
- 51736 CMS LCD: Billing and Coding: Urodynamics CMS LCD
Codes Adjacent To G20.C
Other codes in section G20-G26 (Extrapyramidal and movement disorders).
ICD-10 G20.C, Billing FAQ
Is ICD-10 code G20.C billable? +
Yes, G20.C is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to G20.C? +
ICD-10 G20.C includes: Parkinsonism, NOS.
What codes are Type 1 Excludes for G20.C? +
Type 1 Excludes (never code together with G20.C): Parkinson's disease NOS (G20.A1); Parkinson's disease with dyskinesia (G20.B-); Parkinson's disease without dyskinesia (G20.A-)
Does G20.C affect Medicare Advantage HCC risk adjustment? +
Yes. G20.C maps to CMS-HCC v28 category 78. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with G20.C? +
Procedures frequently paired with G20.C include: 95923, 95924, 95921, 95922, 51741.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on July 17, 2026.
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