G21.9
✓ BillableSecondary parkinsonism, unspecified
Diseases of the nervous system (G00-G99)
❌ Excludes1
inheritedRules inherited from parent codes in the hierarchy.
- • Huntington's disease (G10)
- • neurocognitive disorder with Lewy bodies (G31.83)
- • Shy-Drager syndrome (G90.3)
- • syphilitic Parkinsonism (A52.19)
Clinical Description
ICD-10-CM code G21.9 represents secondary parkinsonism, unspecified. This code falls under the Diseases of the nervous system (G00-G99) classification. It is a billable/specific code valid for HIPAA-covered transactions as of October 1, 2025 (FY2026). This code can be used to indicate a diagnosis for reimbursement purposes on insurance claims.
This is a 5-character code at the 4th level of specificity. This is the most specific code available in this subcategory. Coders should note that G21.9 has 4 Excludes1 restriction(s) — codes that cannot be reported together on the same claim.
Frequently Asked Questions
What is ICD-10 code G21.9?
ICD-10-CM code G21.9 is "Secondary parkinsonism, unspecified". It belongs to the category: Diseases of the nervous system (G00-G99).
Is G21.9 a billable ICD-10 code?
Yes, G21.9 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
What codes are excluded with G21.9?
G21.9 has 4 Excludes1 rule(s). These codes are mutually exclusive and cannot be coded together on the same claim.
Related Codes in G21
Other codes in the same category that may be relevant for differential coding:
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Data Source
CMS ICD-10-CM 2026 Tabular List
Updated October 1, 2025 (FY2026)