Secondary parkinsonism (G21) ICD-10-CM
The G21 code range covers secondary parkinsonism with 10 ICD-10-CM diagnosis codes. 8 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the G21 Range 10 codes · 8 billable
- G21 Secondary parkinsonismNon-billable
- G21.0 Malignant neuroleptic syndrome
- G21.1 Other drug-induced secondary parkinsonismNon-billable
- G21.11 Neuroleptic induced parkinsonism
- G21.19 Other drug induced secondary parkinsonism
- G21.2 Secondary parkinsonism due to other external agents
- G21.3 Postencephalitic parkinsonism
- G21.4 Vascular parkinsonism
- G21.8 Other secondary parkinsonism
- G21.9 Secondary parkinsonism, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the G21 range.
Neuroleptic Malignant Syndrome
A potentially fatal syndrome associated primarily with the use of neuroleptic agents (see ANTIPSYCHOTIC AGENTS) which are in turn associated with dopaminergic receptor blockade (see RECEPTORS, DOPAMINE) in the BASAL GANGLIA and HYPOTHALAMUS, and sympathetic dysregulation. Clinical features include diffuse MUSCLE RIGIDITY; TREMOR; high FEVER; diaphoresis; labile blood pressure; cognitive dysfunction; and autonomic disturbances. Serum CPK level elevation and a leukocytosis may also be present. (From Adams et al., Principles of Neurology, 6th ed, p1199; Psychiatr Serv 1998 Sep;49(9):1163-72)
About the G21 Code Range
Secondary parkinsonism (ICD-10 code G21) covers a group of conditions where parkinsonian symptoms result from external causes such as drugs, toxins, infections, or brain injury rather than primary Parkinson’s disease.
This ICD-10 section includes specific codes for varied causes: G21.0 for malignant neuroleptic syndrome (also known as neuroleptic malignant syndrome), and G21.11 for neuroleptic-induced parkinsonism, which reflect drug-induced cases, particularly from neuroleptic or dopamine-blocking medications. Other codes like G21.19 cover parkinsonism caused by various drugs or toxins including manganese or methanol. Exposure to environmental toxins or poisons such as pesticides, carbon monoxide, or cyanide is coded under G21.2. Post-infectious causes like postencephalitic parkinsonism (G21.3), vascular parkinsonism due to blood vessel issues (G21.4), and other secondary forms from infections, hereditary disorders, or brain injuries are classified under G21.8. When the cause is unspecified, G21.9 is used. Understanding these distinctions helps medical coders select the precise ICD-10 code for documenting secondary parkinsonism accurately.
Questions About This Page
How many billable codes are in the G21 range?
Of the 10 codes in this range, 8 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the G21 range classify?
The range classifies secondary parkinsonism. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
