2027 ICD-10-CM Diagnosis Code G21Secondary parkinsonism

ICD-10-CM Codes›G00–G99›G20-G26›G21

ICD-10-CM G21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G21 is a non-billable ICD-10-CM category code for secondary parkinsonism, so it cannot be submitted on claims. Use a more specific code from this category instead, such as G21.0, G21.11, G21.19, and G21.2.

Code Identity

ICD-10-CM Code
G21
Billable Status
No — Non-Billable Category
Code Describes
Secondary parkinsonism
Short Description
Secondary parkinsonism
Same as the full description in the CMS dataset.
Chapter
G20-G26
Extrapyramidal and movement disorders

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG20-G26Extrapyramidal and movement disorders
CategoryG21Secondary parkinsonism
This CodeG21Secondary parkinsonism

Specific Coding for Secondary parkinsonismOverview

Non-specific codes like G21 require more characters. Use one of these billable codes instead:

  • Use G21.0 for Malignant neuroleptic syndrome

  • G21.1 for Other drug-induced secondary parkinsonism

  • Use G21.11 for Neuroleptic induced parkinsonism

  • Use G21.19 for Other drug induced secondary parkinsonism

  • Use G21.2 for Secondary parkinsonism due to other external agents

  • Use G21.3 for Postencephalitic parkinsonism

  • Use G21.4 for Vascular parkinsonism

  • Use G21.8 for Other secondary parkinsonism

  • Use G21.9 for Secondary parkinsonism, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G21: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

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

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G21, its category, or a range that includes it.

Excludes1 2

These codes carry an Excludes1 note naming G21: they are not reported together with it, unless the two conditions are unrelated.

  • G20.C Parkinsonism, unspecified
    secondary parkinsonism (G21.-)
  • R25 Abnormal involuntary movements
    specific movement disorders (G20-G26) names G20-G26, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming G21: its condition is not part of those codes, and both may be reported when the patient has both.

  • F98.4 Stereotyped movement disorders
    movement disorders of organic origin (G20-G25) names G20-G25, which includes this code

Clinical InformationClinical

  • Parkinson Disease, Secondary

    conditions which feature clinical manifestations resembling primary parkinson disease that are caused by a known or suspected condition. examples include parkinsonism caused by vascular injury, drugs, trauma, toxin exposure, neoplasms, infections and degenerative or hereditary conditions. clinical features may include bradykinesia, rigidity, parkinsonian gait, and masked facies. in general, tremor is less prominent in secondary parkinsonism than in the primary form. (from joynt, clinical neurology, 1998, ch38, pp39-42)

Patient EducationClinical

Parkinson's Disease

Parkinson's disease (PD) is a type of movement disorder. It happens when nerve cells in the brain don't produce enough of a brain chemical called dopamine. Sometimes it is genetic, but most cases do not seem to run in families. Exposure to chemicals in the environment might play a role.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G21Overview

What is the ICD-10 code for secondary parkinsonism?

G21 is the ICD-10-CM category for secondary parkinsonism, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is G21 (Secondary parkinsonism) a billable code?

No. This is a category header that groups the codes for secondary parkinsonism, and headers cannot be submitted on claims. Claims for secondary parkinsonism need a more specific code from this category, such as G21.0, G21.11, and G21.19.

Can G21 be reported with G10?

Not as a rule. The Excludes1 note on G21 lists "Huntington's disease (G10)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).