G20.A2
BillableParkinson's disease without dyskinesia, with fluctuations
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G20.A2 an HCC code?
Yes. G20.A2 maps to Parkinson and Huntington Diseases under the CMS-HCC V28 risk adjustment model (and Parkinson's and Huntington's Diseases under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G20.A2
For G20.A2 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G20.A2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G20.A2 is the ICD-10-CM diagnosis code for parkinson's disease without dyskinesia, with fluctuations. Parkinson's disease without involuntary movements but with motor fluctuations, where symptoms vary throughout the day in response to medication. G20.A2 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering extrapyramidal and movement disorders (g20-g26).
Under the CMS-HCC V28 risk adjustment model, G20.A2 maps to Parkinson and Huntington Diseases (HCC 199) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, G20.A2 maps to Parkinson's and Huntington's Diseases (HCC 78) with a community, non-dual, aged base RAF weight of 0.584. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Motor fluctuations refer to 'on-off' phenomena where medication effectiveness varies. Because G20.A2 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G20.A2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Motor fluctuations refer to 'on-off' phenomena where medication effectiveness varies
- •Document the presence of fluctuations in the clinical notes to support this code selection
Clinical Significance
Parkinson's disease without dyskinesia but with motor fluctuations indicates disease progression where medication effectiveness varies throughout the day, creating 'on' and 'off' periods. This stage signals increasing disease complexity and medication management challenges that drive higher healthcare utilization through more frequent visits and medication adjustments.
Documentation Requirements
- ✓Confirmed Parkinson's disease diagnosis
- ✓Documentation that dyskinesia is absent
- ✓Motor fluctuations explicitly documented (on-off phenomena, wearing-off, end-of-dose deterioration)
- ✓Description of fluctuation pattern and impact on daily function
- ✓Current medication regimen and any recent adjustments
- ✓Levodopa dosing schedule and relationship to symptom control
Commonly Confused Codes
- •G20.A1 — Parkinson's disease without dyskinesia, without fluctuations: no motor fluctuations present
- •G20.B2 — Parkinson's disease with dyskinesia, with fluctuations: has both complications
- •G20.C — Parkinsonism, unspecified: insufficient specificity when fluctuation status is known
- •G20.B1 — Parkinson's disease with dyskinesia, without fluctuations: has dyskinesia but no fluctuations