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G20.B1 ICD-10-CM Code: Parkinson's disease with dyskinesia, without mention of fluctuations

G20.B1 maps to CMS-HCC V28 199. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupG20.B1

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Extrapyramidal and movement disorders (G20-G26)

G20.B1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Parkinson's disease with dyskinesia, without mention of fluctuations

Parkinson's disease with involuntary movements (dyskinesia) but without motor fluctuations, where abnormal involuntary movements occur without significant variation in symptom control.

Buddy the Bee presenting code insight

Buddy Insight

Parkinson's disease with dyskinesia but without fluctuations indicates that involuntary movements (often levodopa-induced) have developed but medication effectiveness remains consistent throughout the day.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 199

Coefficient HCC 199: 0.615 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 119

Code-level coefficient reference

ESRD/PACE

HCC 78

Code-level coefficient reference

RXHCC

HCC 161

Code-level coefficient reference

Code Book Path

Official
G20Parkinson's diseaseG20.BParkinson's disease with dyskinesiaG20.B1Parkinson's disease with dyskinesia, without mention of fluctuations

Inclusion Terms

Official
  • Parkinson's disease with dyskinesia, without mention of OFF episodes
  • HemiparkinsonismInherited from G20
  • Idiopathic Parkinsonism or Parkinson's diseaseInherited from G20
  • Paralysis agitansInherited from G20
  • Primary Parkinsonism or Parkinson's diseaseInherited from G20

Excludes 2

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

Related Codes

Official
G20.B2Parkinson's disease with dyskinesia, with fluctuations

Includes

Official

No Includes notes are included in this display for G20.B1. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • drug induced dystonia (G24.0-)Inherited from G20.B

Code First

Official

No Code First sequencing instructions are included in this display for G20.B1. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code, if applicable, to identify:Inherited from G20
  • dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4)Inherited from G20
  • dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)Inherited from G20
  • dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)Inherited from G20
  • dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)Inherited from G20
  • dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0)Inherited from G20
  • mild neurocognitive disorder due to known physiological condition (F06.7-)Inherited from G20

Code Also

Official

No Code Also instructions are included in this display for G20.B1. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed Parkinson's disease diagnosis
Dyskinesia explicitly documented (chorea, athetosis, dystonia from treatment)
Motor fluctuations documented as absent
Type and severity of dyskinesia described

MEAT Support

HCC Buddy guidance
Confirmed Parkinson's disease diagnosis
Dyskinesia explicitly documented (chorea, athetosis, dystonia from treatment)
Motor fluctuations documented as absent
Type and severity of dyskinesia described

Audit Caution

HCC Buddy guidance
Confusing parkinsonian tremor (disease symptom) with levodopa-induced dyskinesia (treatment complication)
Not documenting whether involuntary movements are dyskinesia from medication or disease progression
Using G20.A1 when documentation describes choreiform or athetoid movements indicating dyskinesia
Failing to distinguish peak-dose dyskinesia from diphasic dyskinesia which may affect treatment decisions

Common Mistakes

HCC Buddy guidance
G20.A1 — Parkinson's disease without dyskinesia, without fluctuations: no dyskinesia present
G20.B2 — Parkinson's disease with dyskinesia, with fluctuations: has both complications
G25.1 — Drug-induced tremor: different movement type and different code category
G24.01 — Drug induced subacute dyskinesia: for dyskinesia caused by drugs other than anti-parkinsonian medications

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is G20.B1 an HCC code?

Yes. G20.B1 (Parkinson's disease with dyskinesia, without mention of fluctuations) maps to HCC 199, Parkinson and Other Degenerative Disease of Basal Ganglia under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.615. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: G20.B1 is billable and maps to V28 HCC 199, Parkinson and Other Degenerative Disease of Basal Ganglia. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
G20.B1
Description
Parkinson's disease with dyskinesia, without mention of fluctuations
HCC (V28)
HCC 199 — Parkinson and Other Degenerative Disease of Basal Ganglia
RAF reference coefficient
0.615
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 199, Parkinson and Other Degenerative Disease of Basal Ganglia
0.615
ESRDHCC 78, Parkinsons and Huntingtons Diseases
Not separately weighted
RxHCCHCC 161, Parkinson Disease
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work G20.B1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G20.B1

For G20.B1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

G20.B1 is the ICD-10-CM diagnosis code for parkinson's disease with dyskinesia, without mention of fluctuations. Parkinson's disease with involuntary movements (dyskinesia) but without motor fluctuations, where abnormal involuntary movements occur without significant variation in symptom control. G20.B1 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.B1 maps to Parkinson and Other Degenerative Disease of Basal Ganglia (HCC 199) with a source-labeled community, non-dual, aged reference coefficient of 0.615. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Dyskinesia includes chorea, athetosis, and other involuntary movements. For G20.B1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for G20.B1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Dyskinesia includes chorea, athetosis, and other involuntary movements
  • •Ensure dyskinesia is documented separately from tremor or rigidity

Clinical Significance

Parkinson's disease with dyskinesia but without fluctuations indicates that involuntary movements (often levodopa-induced) have developed but medication effectiveness remains consistent throughout the day. Dyskinesia represents a significant treatment complication that may require medication adjustments, surgical intervention consideration, or deep brain stimulation evaluation.

Documentation Requirements

  • ✓Confirmed Parkinson's disease diagnosis
  • ✓Dyskinesia explicitly documented (chorea, athetosis, dystonia from treatment)
  • ✓Motor fluctuations documented as absent
  • ✓Type and severity of dyskinesia described
  • ✓Relationship of dyskinesia to medication timing
  • ✓Impact of dyskinesia on daily functioning and quality of life

Commonly Confused Codes

  • •G20.A1: Parkinson's disease without dyskinesia, without fluctuations: no dyskinesia present
  • •G20.B2: Parkinson's disease with dyskinesia, with fluctuations: has both complications
  • •G25.1: Drug-induced tremor: different movement type and different code category
  • •G24.01: Drug induced subacute dyskinesia: for dyskinesia caused by drugs other than anti-parkinsonian medications

Child Codes

G20.B1Parkinson's disease with dyskinesia, without mention of fluctuations
HCC 199
G20.B2Parkinson's disease with dyskinesia, with fluctuations
HCC 199

Code Hierarchy

└G20Parkinson's disease└G20.BParkinson's disease with dyskinesia└G20.B1Parkinson's disease with dyskinesia, without mention of fluctuations
└G20.B1Parkinson's disease with dyskinesia, without mention of fluctuations

G20.B1 code history

Code setChange
FY2024 (effective Oct 1, 2023)Added to the code set

Source: official CMS ICD-10-CM order and addenda files, FY2016 through FY2027.

Also searched as

  • G20 B1
  • G20B1

For G20.B1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

G20.B1 maps to CMS-HCC V28 category 199, Parkinson and Other Degenerative Disease of Basal Ganglia. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for G20.B1. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

Work G20.B1 in HCC Buddy

Open G20.B1 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

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