Understanding CMS HCC v28 in 5 Minutes

What every provider needs to know about the new risk-adjustment model 

If you work in Medicare Advantage (MA), ACO REACH, or any value-based program, CMS’s move to the HCC v28 risk-adjustment model is not just a payer problem—it directly affects how your documentation turns into dollars and how your sickest patients are “seen” by the system. 

Here’s a 5-minute, clinically grounded walkthrough you can use with your admin, coding, and finance teams. 

Minute 1 – What is the HCC model (and why should I care)? 

CMS’s Hierarchical Condition Category (HCC) model is the engine that turns diagnoses into a risk score (RAF). That RAF score adjusts per-member-per-month payments in: 

• Medicare Advantage (MA) 

• ACO REACH and other CMMI models 

• Certain risk-sharing and total cost of care contracts 

  
  

Key points: 

• Average Traditional Medicare beneficiary = RAF 1.0. 

• Higher clinical complexity → more HCCs → higher RAF → higher benchmark/payment. CMS 

• HCCs are not every ICD-10 code; they are a curated set of clinically similar condition groups (e.g., “Diabetes with chronic complications”). 

  
  

Historically, the model (v24 and earlier) has been criticized because plans and provider groups could increase payment through aggressive documentation and coding practices, even when true disease burden didn’t change. MedPAC 

That’s the backdrop for HCC v28. 

Minute 2 – What changed in HCC v28? 

CMS rebuilt the model and is phasing it in from 2024–2026.  

Major shifts: 

1. Directly ICD-10–based model 

   1. v24 used an ICD-10 → ICD-9 → condition → HCC pipeline. 

   2. v28 maps directly from ICD-10 to HCCs, improving clinical specificity and alignment with current coding practice.  

2. More granular HCC structure 

   1. The number of condition indicators increased (e.g., ~79 to 115 in one widely cited analysis), providing finer stratification of disease categories—especially for cardiovascular disease, kidney disease, mental health, and diabetes. MedPAC 

3. Removal / down-weighting of “high-leverage, low-cost” conditions 

   CMS explicitly targeted HCCs that had become magnets for coding intensity rather than true cost: 

   1. Protein-calorie malnutrition 

   2. Certain angina and atherosclerosis codes 

   3. Some conditions with highly variable documentation practices These are suppressed or significantly down-weighted in v28. MedPAC 

4. Constrained coefficients for certain hierarchies 

   1. Diabetes HCCs (no complications, chronic complications, acute complications) share constrained coefficients to reduce outsized payment differences driven by coding detail alone. 

   2. Similar constraints are applied to some heart failure categories. MedPAC 

5. Calibration to more recent FFS data 

   1. Coefficients are recalibrated on more recent Traditional Medicare data, which affects relative weights across chronic conditions and interactions.  

In plain language: v28 is stricter, more granular, and explicitly designed to blunt the impact of “upcoding-heavy” diagnoses. 

 

Minute 3 – How and where is v28 being phased in?

CMS is not flipping a single switch—it’s a multi-year blend: 

• 2024: Start of v28 phase-in for MA (partially blended with v24). 

• 2025: CMS applies a 67% / 33% blend (67% v28, 33% v24) for MA, and similar blending for ACO REACH/Kidney Care Choices with their Part C risk adjustment alignment. CMS 

• 2026: Expected to be fully v28-based for MA (barring policy changes). Becker's Payer Issues  

  
  

In parallel, MedPAC estimates that MA payments are ~20% higher than FFS in 2025 (about $84B more), driven by coding intensity and favorable selection. CMS and MedPAC explicitly point to model reforms like v28 and coding intensity adjustments as key levers to rein this in. MedPAC 

For you, that means: 

• Your RAF scores may drift down even if you code the same way as last year. 

• Benchmarks in ACO REACH/Kidney Care models are also being recalibrated with Part C (v28) alignment and caps on risk score growth. CMS 

Minute 4 – What does v28 mean for providers on the ground?

From a provider and coding perspective, v28 changes what “counts,” how much it counts, and how risky coding gaps become. 

1. Some diagnoses “matter less” for payment 

Conditions that historically yielded meaningful RAF bumps (e.g., malnutrition, some vascular codes, angina) may now: 

• Map to non-payment HCCs, or 

• Have substantially lower coefficients. MedPAC 

  
  

This doesn’t mean they’re clinically unimportant—but they will drive less revenue signal. 

2. Complexity and combinations matter more than isolated labels 

Because of constrained coefficients and more granular hierarchies, the model better differentiates: 

• Truly complex chronic disease (e.g., diabetes + advanced CKD + heart failure) 

• Versus “diagnosis stacking” without consistent evidence in the chart. MedPAC 

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That increases the importance of: 

• Longitudinal evidence (labs, imaging, notes) 

• Clear links between ICD-10 codes and the assessment & plan 

  
  

3. Coding intensity is under a microscope 

A growing body of literature shows that differential coding practices in MA drove billions in additional payments: 

• One study in Annals of Internal Medicine estimated $33B in extra payments in 2021 from coding differences, with CMS explicitly citing v28 as a tool to reduce the MA–FFS risk-score gap. Becker's Payer Issues  

• MedPAC finds that most MA enrollees are in contracts where coding intensity exceeds CMS’s adjustment, and cites multiple Health Affairs / HSR studies documenting persistent upcoding. MedPAC 

Translation: CMS expects risk scores to come down—and is okay with that. If your organization’s RAF performance depends on aggressive rather than accurate documentation, v28 will expose that. 

4. SNFs, LTC, and complex-care providers are in a “barbell” zone 

For SNFs, LTC, and high-acuity primary care: 

• Patients often truly have high disease burden (CKD 4–5, CHF, dementia, frailty, multimorbidity). 

• But documentation is fragmented across EMR encounters, hospitalizations, and post-acute transitions. 

In v28, missing a single key condition (e.g., advanced CKD) in a year can have a larger relative impact on RAF than before, because the model leans more heavily on accurate capture of genuinely expensive chronic illness and less on edge-case diagnoses. 

 

Minute 5 – How should providers respond? 

Here’s a pragmatic playbook you can act on now. 

1. Re-educate teams on which conditions “drive the model” 

Don’t treat v28 as just a payer issue. Your clinical, coding, and quality teams should know: 

• Which chronic condition families are most impactful in v28 (e.g., CHF, CKD, diabetes, pulmonary disease, serious mental illness). MedPAC 

• Which historically “favorite” codes (e.g., protein-calorie malnutrition) are now much less impactful. 

Use short, condition-focused refreshers rather than long coding seminars—anchored in real patients and charts. 

2. Tighten the link between documentation and ICD-10 

In a stricter model, sloppy documentation is more expensive: 

• Make sure Assessment & Plan clearly supports each HCC-relevant diagnosis. 

• Reduce over-reliance on problem list carry-forward; reconcile active vs historical conditions. 

• Encourage clinicians to document severity and chronicity (e.g., CKD stage, HF with reduced EF, insulin-use in diabetes) when clinically accurate. 

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3. Shift from “chasing codes” to clinical reasoning + evidence 

Risk adjustment under v28 rewards: 

• Coherent clinical stories 

• Longitudinal follow-up of chronic disease 

• Evidence of active management (labs, meds, referrals, plans) 

That’s why we focus on clinical reasoning AI rather than just NLP: 

• Instead of surfacing every possible code, we prioritize conditions where documentation and evidence clearly support persistent, costly disease. 

• We align nudges and gap closure recommendations with v28’s structure, so you’re not optimizing for a model that’s already going away. 

(You don’t need to mention this in your internal policy—but it’s how we think about building tools for your teams.) 

4. Stress-test your RAF and revenue under v28 assumptions 

Work with analytics / actuarial partners to: 

• Simulate RAF under v24 vs v28 using your existing population. 

• Identify which conditions, practices, or facilities drive the largest delta. 

• Prioritize high-impact cohorts: multi-morbid patients in SNFs, LTC, complex primary care panels, dual-eligibles. 

This turns v28 from a source of “rate shock” into a roadmap for documentation and care improvement. 

• HCC v28 is here and phasing in through 2026—it’s not theoretical anymore. 

• The model is more granular and stricter, directly ICD-10–based and explicitly targeting high-leverage coding intensity. 

• Expect RAF scores and payments to compress, especially where coding intensity was driving revenue. 

• Clinically coherent documentation, longitudinal evidence, and accurate capture of true complexity will matter more than ever. 

• If you’re in SNF/LTC or complex primary care, v28 can help you—if you have the data and workflows to surface and document the real burden of disease consistently. 

References 

1. Centers for Medicare & Medicaid Services (CMS). Advance Notice of Methodological Changes for Calendar Year 2024 for Medicare Advantage Capitation Rates and Part C and Part D Payment Policies (Fact Sheet). CMS Newsroom; 2023–2024.  

2. Centers for Medicare & Medicaid Services (CMS). Risk Adjustment. CMS.gov. Accessed 2025. Becker's Payer Issues | Payer News 

3. Carlin CS, Feldman R, Jung J. The mechanics of risk adjustment and incentives for coding intensity in Medicare. Health Services Research. 2024;59(3):e14272. PMCID: PMC11063086. MedPAC 

4. Medicare Payment Advisory Commission (MedPAC). Report to the Congress: Medicare Payment Policy. Chapter 11: The Medicare Advantage Program—Status Report. March 2025. 

5. Johnson A. Coding Intensity in Medicare Advantage and Part D. MedPAC public meeting presentation; June 2025. MedPAC 

6. Curto VE, Politzer E, et al. Coding intensity variation in Medicare Advantage. Health Affairs Scholar. 2025;3(1). (Cited in MedPAC 2025 coding intensity review.) MedPAC 

7. Emerson J. Medicare Advantage coding differences drove $33B in extra payments: Study. Becker’s Payer Issues. April 16, 2025. Summarizing a study published in Annals of Internal Medicine on differential coding and MA payments. Becker's Payer Issues | Payer News 

8. Centers for Medicare & Medicaid Services (CMS). ACO REACH and Kidney Care Choices Models: PY2025 Risk Adjustment. 2024–2025. CMS