What does ICD-10 code G21 mean?

ICD-10 code G21 is the standardized code used for secondary parkinsonism in medical records and coding systems.

When is ICD-10 code G21 used?

Doctors, hospitals, and insurers may use ICD-10 code G21 when recording secondary parkinsonism in a standardized format. This entry may also act as a broader category that points toward more specific child codes.

Does ICD-10 code G21 confirm a diagnosis?

No. A code helps standardize documentation and claims, but it should not be read as a substitute for a clinician's full assessment.

ICD10

ICD-10 Code G21: Secondary parkinsonism

Name: ICD-10 Code G21: Secondary parkinsonism
Creator: HealthAssure Clinical Team
Published: 2026-05-21T06:06:47.435Z

G21 is an ICD-10 diagnosis entry used to group records related to Secondary parkinsonism. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

When is it used?

May be used when a clinician documents secondary parkinsonism in a patient's medical record.
May appear in hospital records, claims, referrals, and clinical documentation.
This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

A code alone does not explain severity, treatment plan, or outcome.
A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter

6Diseases of the nervous system (G00-G99)

block

G20-G26Extrapyramidal and movement disorders

currentG20-G26

Official coding notes

Excludes1 (do not code together)

Huntington's disease (G10)
neurocognitive disorder with Lewy bodies (G31.83)
Shy-Drager syndrome (G90.3)
syphilitic Parkinsonism (A52.19)

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

NeurologistGeneral Physician

Sibling codes

G20Parkinson's disease G23Other degenerative diseases of basal ganglia G24Dystonia G25Other extrapyramidal and movement disorders G26Extrapyramidal and movement disorders in diseases classified elsewherebillable

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.

Legacy codes

G21

Replacement codes

G21.0 — Malignant neuroleptic syndromeG21.2 — Secondary parkinsonism due to other external agentsG21.3 — Postencephalitic parkinsonismG21.4 — Vascular parkinsonismG21.8 — Other secondary parkinsonismG21.9 — Secondary parkinsonism, unspecified

Common synonyms

Secondary parkinsonism

Frequently asked questions

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.