ICD-10-CM 2027 diagnosis code

G21Secondary parkinsonism

Not billable — use a more specific code

G21 is a header code, so it can't be reported by itself. Choose one of the 7 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G21

G21 is the ICD-10-CM diagnosis code for secondary parkinsonism. It belongs to block G20-G26 (extrapyramidal and movement disorders) and chapter 6 (diseases of the nervous system). It is a header code, so it can't be reported by itself; one of its 7 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: G21.0 (syndrome), G21.1 (parkinsonism), G21.2 (due to other external agents), G21.3 (parkinsonism), G21.4 (parkinsonism), G21.8 (parkinsonism) and G21.9 (unspecified).

Don't report G21 together with the conditions in its Excludes1 note: Huntington's disease (G10), neurocognitive disorder with Lewy bodies (G31.83), Shy-Drager syndrome (G90.3) and syphilitic Parkinsonism (A52.19).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under G21

Coding notes

Excludes1Not coded here — never report together with this code

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

Notes that apply from higher levels

Instructions written at a parent level also apply to G21.

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Codes whose notes reference G21

G20.CExcludes1

Code history

2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about G21

Is G21 billable?: No. G21 is a header code. Report one of its more specific subcodes instead.