G83.21
BillableMonoplegia of upper limb affecting right dominant side
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G83.21 an HCC code?
Yes. G83.21 maps to Monoplegia, Other Paralytic Syndromes under the CMS-HCC V28 risk adjustment model (and Monoplegia, Other Paralytic Syndromes 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 G83.21
For G83.21 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 G83.21 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G83.21 is the ICD-10-CM diagnosis code for monoplegia of upper limb affecting right dominant side. Weakness or paralysis affecting only the right arm in a person whose right side is their dominant side. G83.21 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering cerebral palsy and other paralytic syndromes (g80-g83).
Under the CMS-HCC V28 risk adjustment model, G83.21 maps to Monoplegia, Other Paralytic Syndromes (HCC 254) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, G83.21 mapped to the same category but with a base RAF weight of 0.304 — V28 recalibrated weights across the entire model. 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.
Verify that only the upper limb is affected; if the lower limb is also involved, use a different code. Because G83.21 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 G83.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify that only the upper limb is affected; if the lower limb is also involved, use a different code
- •Document the functional impact on the dominant arm, as this may affect rehabilitation and treatment planning
Clinical Significance
Monoplegia of the upper limb affecting the right dominant side is one of the most functionally devastating monoplegia presentations, as most people rely heavily on their dominant hand for writing, eating, grooming, and work tasks. Loss of dominant arm function requires extensive occupational therapy to develop compensatory strategies with the nondominant hand. This code captures maximum specificity for risk adjustment and clinical documentation.
Documentation Requirements
- ✓Documentation of monoplegia isolated to the right upper extremity
- ✓Right-hand dominance confirmed
- ✓Underlying etiology documented and coded separately
- ✓Motor strength examination findings
- ✓Functional impact on handwriting, self-care, and occupational tasks
- ✓Occupational therapy and rehabilitation plan
- ✓Adaptive equipment needs