G21.9: Secondary parkinsonism, unspecified
G21.9, secondary parkinsonism, unspecified, is listed as a covered diagnosis in 6 Medicare billing and coding articles that apply to 20 HCPCS Level II codes, including G0451 (Development testing, with interpretation and report, per…), G0152 (Services performed by a qualified occupational therapist…), G0155 (Services of clinical social worker in home health or…). The articles come from 4 Medicare contractors. A listed diagnosis supports medical necessity only; coverage still depends on the LCD's criteria and on documentation in the medical record.
HCPCS Level II codes with G21.9 as a covered diagnosis
| Code | Description | Medicare coverage | DMEPOS fee 2026 (state range) | Articles listing it |
|---|---|---|---|---|
| G0451 | Development testing, with interpretation and report, per standardized instrument form | Carrier judgment | — | 2 |
| G0152 | Services performed by a qualified occupational therapist in the home health or hospice setting, each 15 minutes | Carrier judgment | — | 1 |
| G0155 | Services of clinical social worker in home health or hospice settings, each 15 minutes | Carrier judgment | — | 1 |
| G0156 | Services of home health/hospice aide in home health or hospice settings, each 15 minutes | Carrier judgment | — | 1 |
| G0299 | Direct skilled nursing services of a registered nurse (rn) in the home health or hospice setting, each 15 minutes | Carrier judgment | — | 1 |
| G0300 | Direct skilled nursing services of a licensed practical nurse (lpn) in the home health or hospice setting, each 15 minutes | Carrier judgment | — | 1 |
| G0410 | Group psychotherapy other than of a multiple-family group, in a partial hospitalization or intensive outpatient setting, approximately 45 to 50 minutes | Carrier judgment | — | 1 |
| G0017 | Psychotherapy for crisis furnished in an applicable site of service (any place of service at which the non-facility rate for psychotherapy for crisis services applies, other than the office setting); first 60 minutes | Carrier judgment | — | 1 |
| G0018 | Psychotherapy for crisis furnished in an applicable site of service (any place of service at which the non-facility rate for psychotherapy for crisis services applies, other than the office setting); each additional 30 minutes (list separately in addition to code for primary service) | Carrier judgment | — | 1 |
| G0411 | Interactive group psychotherapy, in a partial hospitalization or intensive outpatient setting, approximately 45 to 50 minutes | Carrier judgment | — | 1 |
| G2187 | Patients with clinical indications for imaging of the head: head trauma | Carrier judgment | — | 1 |
| G2188 | Patients with clinical indications for imaging of the head: new or change in headache above 50 years of age | Carrier judgment | — | 1 |
| G2189 | Patients with clinical indications for imaging of the head: abnormal neurologic exam | Carrier judgment | — | 1 |
| G2190 | Patients with clinical indications for imaging of the head: headache radiating to the neck | Carrier judgment | — | 1 |
| G2191 | Patients with clinical indications for imaging of the head: positional headaches | Carrier judgment | — | 1 |
| G2192 | Patients with clinical indications for imaging of the head: temporal headaches in patients over 55 years of age | Carrier judgment | — | 1 |
| G2193 | Patients with clinical indications for imaging of the head: new onset headache in pre-school children or younger (<6 years of age) | Carrier judgment | — | 1 |
| G2194 | Patients with clinical indications for imaging of the head: new onset headache in pediatric patients with disabilities for which headache is a concern as inferred from behavior | Carrier judgment | — | 1 |
| G2195 | Patients with clinical indications for imaging of the head: occipital headache in children | Carrier judgment | — | 1 |
| G0255 | Current perception threshold/sensory nerve conduction test, (snct) per limb, any nerve | Non-covered by Medicare | Not covered | 1 |
Medicare policy articles listing G21.9
- A56756: Billing and Coding: Home Health - Psychiatric Care (Palmetto GBA (HHH MAC); 5 Level II codes). LCD with the same title: L34561
- A57480: Billing and Coding: Psychiatry and Psychology Services (WPS Insurance Corporation (MAC - Part A, MAC - Part B); 4 Level II codes). LCD with the same title: L33632, L34616
- A56937: Billing and Coding: Psychiatry and Psychology Services (Wellpoint Federal (MAC - Part A, MAC - Part B); 1 Level II codes). LCD with the same title: L33632, L34616
- A57780: Billing and Coding: Psychological and Neuropsychological Tests (First Coast Service Options, Inc. (MAC - Part A, MAC - Part B); 1 Level II codes). LCD with the same title: L34520
- A56619: Billing and Coding: Nerve Conduction Studies and Electromyography (Palmetto GBA (MAC - Part A, MAC - Part B); 1 Level II codes). LCD with the same title: L34594, L34859, L35048, L35081
- A56612: Billing and Coding: CT of the Head (Palmetto GBA (MAC - Part A, MAC - Part B); 9 Level II codes). LCD with the same title: L34417
A diagnosis listed as covered in a billing and coding article supports medical necessity for the article's codes; it does not guarantee payment. Coverage depends on the LCD's criteria, the contractor's jurisdiction and documentation in the medical record.
Other G21 diagnoses (Secondary parkinsonism)
- G21.0 — Malignant neuroleptic syndrome
- G21.11 — Neuroleptic induced parkinsonism
- G21.19 — Other drug induced secondary parkinsonism
- G21.2 — Secondary parkinsonism due to other external agents
- G21.3 — Postencephalitic parkinsonism
- G21.4 — Vascular parkinsonism
- G21.8 — Other secondary parkinsonism
Frequently asked questions
Does Medicare cover G21.9 (Secondary parkinsonism, unspecified)?
Medicare covers items and services, not diagnoses. 6 Medicare billing and coding articles list G21.9 as a covered diagnosis for 20 HCPCS Level II codes: the diagnosis can support medical necessity for those codes, but payment still depends on the LCD's coverage criteria and the medical record.
Which HCPCS codes can be billed with ICD-10 G21.9?
The Level II codes from the policies most specific to this diagnosis are G0451 (Development testing, with interpretation and report, per…, 2 articles); G0152 (Services performed by a qualified occupational therapist…, 1 article); G0155 (Services of clinical social worker in home health or…, 1 article); G0156 (Services of home health/hospice aide in home health or…, 1 article); G0299 (Direct skilled nursing services of a registered nurse (rn)…, 1 article). Code choice depends on the item supplied; check each code's descriptor.
Which Medicare policy articles list G21.9?
A56756 (Billing and Coding: Home Health - Psychiatric Care); A57480 (Billing and Coding: Psychiatry and Psychology Services); A56937 (Billing and Coding: Psychiatry and Psychology Services), and 3 more articles.
What is ICD-10-CM code G21.9?
G21.9 is the ICD-10-CM code for secondary parkinsonism, unspecified, in category G21 (Secondary parkinsonism), chapter 6: Diseases of the nervous system.
Next steps
- Run a reimbursement report for a device billed under G0451
- Watch G0451 for fee, coverage and descriptor changes
- Build a full Medicare revenue model for G0451
Sources: CMS Medicare Coverage Database billing and coding articles (covered ICD-10 code lists and HCPCS links); ICD-10-CM FY2026; CMS HCPCS Level II release October 2026; CMS DMEPOS fee schedule 2026 (non-rural state fees). Not billing or legal advice.
Chapter 6: Diseases of the nervous system · All diagnoses · HCPCS lookup