G20.C vs G21
G20.C (Parkinsonism, unspecified) compared with G21 (Secondary parkinsonism), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. G20.C carries an Excludes1 note covering G21: “secondary parkinsonism (G21.-)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| G20.CParkinsonism, unspecified | G21Secondary parkinsonism | |
|---|---|---|
| Billing status | Billable | Non-billable header |
| Classification | G00-G99 — Diseases of the Nervous System (G00-G99) | G00-G99 — Diseases of the Nervous System (G00-G99) |
| Definition | Parkinsonism, unspecified is a billable ICD-10-CM diagnosis code (G20.C). | Secondary parkinsonism is a non-billable ICD-10-CM category code (G21). |
| Includes | Parkinsonism, NOS | — |
| Use additional code | code, if applicable, to identify: dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4) dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-) | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources