Is ICD-10-CM code G21 billable?

No, G21 (Secondary parkinsonism) is a non-billable ICD-10-CM code. It must be coded to a more specific subcategory before it can be used for reimbursement.

What chapter does ICD-10-CM code G21 belong to?

G21 belongs to Chapter 6 of the ICD-10-CM tabular list: G00–G99 (Diseases of the Nervous System).

G21Not billable, use a more specific code below

Secondary parkinsonism

In Extrapyramidal and movement disorders (G20-G26), chapter 6: Diseases of the Nervous System

8 billable codes under G21: 1 is an MCC, 6 are a CC; 4 map to HCC 199 (Parkinson and Other Degenerative Disease of Basal Ganglia).A CC or MCC (major CC) is a secondary diagnosis that raises the MS-DRG payment. An HCC counts toward a Medicare Advantage patient's risk score.

Instructional notes

Excludes1: not coded here, use a different code

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

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers default dominant or nondominant side for hemiplegia and monoplegia, and use and sequencing of G89 pain codes, including postoperative, chronic, and neoplasm-related pain.

Dominant/nondominant side (page 45)
Pain - Category G89 (page 45)

Read Section I.C.6 (page 45)

All codes under G21

G21 can't be used on a claim. Pick a billable code below; grey headings group them.

G21 MS-DRGs

As the principal diagnosis, the billable codes under G21 group to MS-DRG 056, 057, 091, 092, or 093 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

DRG 056 Degenerative Nervous System Disorders with MCC (7 of 8 codes)
DRG 057 Degenerative Nervous System Disorders without MCC (7 of 8 codes)
DRG 091 Other Disorders of Nervous System with MCC (1 of 8 codes)
DRG 092 Other Disorders of Nervous System with CC (1 of 8 codes)
DRG 093 Other Disorders of Nervous System without CC/MCC (1 of 8 codes)

Other codes that refer to G21

Notes on these codes point to G21.

G20.C Excludes1: secondary parkinsonism (G21.-)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

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.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.