Healthcare has come a long way from what it used to be.
Imagine a patient walking into the doctor’s office, handing over a few dollars in cash, and walking out with no bills, claims, or paperwork. That was healthcare in America not so long ago.
Then came employer-sponsored insurance, followed by the launch of Medicare and Medicaid in 1965. These programs dramatically expanded access to care for everyone and introduced new layers of billing rules, coding systems, and regulatory requirements. By the 1990s, Revenue Cycle Management (RCM) emerged to bring structure to the increasingly complex process of getting paid for healthcare services.
Despite all the progress, one of the biggest ongoing and expensive challenges in healthcare is Hierarchical Condition Category (HCC) coding, a model developed by the Centers for Medicare & Medicaid Services (CMS) to align payments with the severity and complexity of a patient’s health conditions. The goal is to match reimbursement with clinical risk, but errors in HCC coding can lead to lost revenue, compliance audits, and underpayment for high-risk patient care.
This blog post explores the HCC model and explains how it works.
Understanding the HCC Model and Its Role in Risk-Based Reimbursement
Understanding the HCC model starts with understanding Risk Adjustment.
There was a time when payers reimbursed healthcare providers the same amount whether they treated something simple like the common cold or something complex and costly like cancer. This created a severe imbalance. Providers caring for high-risk, medically complex patients were often underpaid, while those mainly treating healthy populations could be overpaid.
Risk Adjustment was introduced to correct that imbalance by aligning payments with the actual cost of care. It predicts the expected expense per patient based on the complexity of care and helps ensure that reimbursement better reflects how much care a patient actually needs.
This shift moved healthcare reimbursement from fee-for-service (volume-based) to value-based care, where payments are based on quality and clinical complexity. Providers are no longer paid just for how many patients they see, but also for how sick those patients are, how well they’re managed, and how accurately their conditions are documented and coded.
At the center of this shift is the HCC risk adjustment model. HCC stands for Hierarchical Condition Categories, a model that groups similar chronic conditions together to estimate the clinical risk and cost of treating a patient. Developed by CMS, it’s designed to ensure that payments reflect the true clinical complexity of a patient’s health status.
Providers use ICD-10 diagnosis codes to document chronic conditions like diabetes, heart failure, or kidney disease. These diagnoses are then grouped into HCC categories; each assigned a value based on the expected cost of managing that condition. However, not all diagnoses contribute to HCC risk adjustment, only specific ICD-10 codes “map” to HCC categories. That means if a provider documents a condition that doesn’t have an assigned HCC, it won’t impact the patient’s RAF score.
You might be wondering: what are RAF scores?
The Risk Adjustment Factor (RAF) is a score that predicts the patient’s expected healthcare costs for the year. The more complex the patient’s conditions, the higher the score.
While HCC coding is based on diagnosis codes (like diabetes, heart failure, etc.), the final RAF score, includes more than just medical conditions. It considers several demographic factors for pay-out, including:
Age– Older patients generally require more care.
Gender– Some conditions and risk profiles differ by sex.
Disability status– Indicates complex care needs.
Insurance status (Medicare, Medicaid, or dual-eligible) – Socioeconomic hardship may lead to higher health risks.
Institutional status (e.g., nursing home) – Suggests higher baseline care costs.
HCC coding is also calendar-year based, which means all chronic conditions must be re-documented and coded every year. If a provider doesn’t code a condition annually—even if the patient still has it—it falls off the record, lowering the RAF score and potentially reducing payment.
Real-Life Example: How HCC Coding Impacts Risk Adjustment
Two Medicare Advantage patients, Maria and James, are both 68 years old and visit the same primary care clinic.
Maria has controlled high blood pressure and no other chronic conditions.
→ Her HCC risk score: 0.45
James has diabetes, congestive heart failure (CHF), and chronic kidney disease (CKD).
→ His HCC risk score: 2.1
Patient
Age
Chronic Conditions
Mapped HCCs
RAF Score
Maria
– Controlled hypertension
– None (controlled hypertension doesn’t map to HCC)
0.45
James
– Diabetes- Congestive Heart Failure (CHF)- Chronic Kidney Disease (CKD)
– HCC 18 (Diabetes) – HCC 85 (CHF) – HCC 134 (CKD)
2.10
Although they’re the same age, James is far more likely to need hospitalizations, lab work, medications, and specialist care throughout the year.
Using the HCC model, Medicare assigns higher reimbursement to James’s care team because his coded diagnoses reflect a higher clinical risk. This is how Risk Adjustment works: predicting the cost of care based on each patient’s documented health conditions and adjusting payment accordingly.
If James’s provider fails to document and code all his chronic conditions, his HCC score would drop, and reimbursement would be lower than it should be, even though his care still requires more resources.
Model update: CMS-HCC V28 and social determinants of health
The HCC numbers and scores in the example above are illustrative and use V24 category labels. CMS is phasing in the 2024 CMS-HCC model (V28) for Medicare Advantage payment: a blend of 67% V24 and 33% V28 in 2024, 33% V24 and 67% V28 in 2025, and 100% V28 in payment year 2026. V28 renumbers many categories and some diagnosis codes no longer map to a payment HCC, so check the current CMS mappings before coding.
Social determinants of health Z codes (Z55–Z65) should be documented because they inform care planning and quality programs, but they do not raise a patient’s CMS-HCC risk score. Coding should always follow the ICD-10-CM guidelines and the provider’s documentation, and complex cases should be reviewed by a certified risk adjustment coder.
Final Thought:
HCC coding and RAF is all about making sure doctors and care teams get paid fairly for treating patients with complex health needs. When conditions are properly documented and coded, payments better reflect the real cost of care. It’s a key part of building a healthcare system that supports both patients and providers.
Up Next: Common HCC Coding Mistakes and How to Prevent Them
Now that we’ve covered the basics of the HCC model and risk adjustment, the next blog will dive into:
Common HCC coding errors
Their financial and compliance impacts
Practical strategies to prevent them