Every Medicare Advantage patient you see arrives with a health story, and hierarchical condition category (HCC) coding is how that story gets translated into data the payer can read. When it is thin, the picture is wrong, and the gap shows up later in payments, quality scores and audits. This guide explains how HCC coding works, what changed with CMS-HCC V28, and how physicians and practice managers can document with confidence.
What Is HCC Coding?
The HCC coding system is a hierarchical categorisation of ICD-10-CM diagnosis codes into related groups to help predict the level of care required by the patient.
These are grouped into categories that have a numerical weight and represent clinically similar diagnoses. In a similar group of diseases, the “hierarchy” applies: Only the most serious diagnosis is taken into account. HCC models are used for Medicare Advantage (MA) plans, Accountable Care Organizations (ACOs) and some Affordable Care Act (ACA) plans.
To physicians, the practicalities are straightforward. You will use the diagnosis codes you report to claims and encounter notes to directly drive this model, which is why the quality of your coding and documentation matters.
Why HCC Coding Matters
HCC coding is important because it is what converts the clinical record into a measure that defines patient complexity which in turn influences funding for health plans and ACOs to take care of patients. An accurate record of a patient’s chronic conditions enables appropriate care planning, fair benchmarks and meaningful quality reporting.
Only half of patients have chronic conditions recorded, IMO Health says. This is IMO’s own experience, not a CMS statistic, but that’s what many practices will find when they review their charts. Conditions are controlled in the exam room, but never coded.
A problem list which is shared with a care team that can see the entire list is better positioned to coordinate referrals, medications and follow-up.
Which Conditions Map to HCCs?
Many chronic, long-term conditions map to HCCs, and the most common ones are the ones physicians treat every day. Examples include:
- Diabetes, with or without complications
- Chronic obstructive pulmonary disease (COPD) and severe asthma
- Major depression and bipolar disorder
- Breast, prostate, lung and colorectal cancers
- Rheumatoid arthritis
A condition must be chronic or clinically significant enough to predict future cost, and it must be supported in a face-to-face or qualifying telehealth encounter. This is because your coding team needs to review the existing CMS mappings annually, and not on memory.
How Risk Adjustment and the RAF Score Work
To adjust payments to health plans for risk, CMS takes into account the need for more (or fewer) services and payment per patient. The outcome is a risk adjustment factor (RAF) score, which incorporates a demographic score and the weights of the patient’s known HCCs.
The CMS calculates a RAF(Risk Adjustment Factor) score by adding together three parts: a demographic factor (age, sex, Medicaid status, etc.), a disease factor (sum of the HCC weights), and, in some instances, interaction factors for some combinations of conditions. The total is then multiplied by a base rate, which yields a payment to the plan per member per month (PMPM). A lower RAF score is obtained by a healthy patient. A patient with multiple chronic medical conditions receives more than one.
A Step-by-Step RAF Example
These are examples of numbers, not official CMS coefficients. They display the arithmetic without the decimal points. Now, a 74-year-old woman with type 2 diabetes who has chronic kidney complications, stage 3 CKD, and COPD, all of which were establish and confirmed this year.
| Step | Component | Illustrative value |
|
1 |
Demographic score (age and sex) |
0.45 |
|
2 |
Diabetes with chronic complications |
0.17 |
|
3 |
CKD, stage 3 |
0.13 |
|
4 |
COPD |
0.32 |
|
5 |
Total RAF score (add steps 1 to 4) |
1.07 |
|
6 |
Illustrative base rate (PMPM) |
$1,000 |
|
7 |
Estimated PMPM payment (RAF × base rate) |
$1,070 |
Even though her care needs did not change, the COPD was never document, and the plan funding for this patient would be reduce, with the score to 0.75. Risk adjustment is intended to avoid such a mismatch. The same applies in reverse as well, and hence, unsupported diagnoses pose a compliance risk.
How HCC Coding Affects Billing and Reimbursement
HCC coding impact on reimbursement is due to the fact that plans and risk-bearing groups are paid and judge on the conditions describe in patient records. If your panel is under-document, your data will not reflect the complexity of your panel; if your documentation is vague, your codes won’t have a risk weight.
Specificity is the key. Though the word “diabetes” might not provide much clarity, the term “diabetes mellitus type 2 with diabetic chronic kidney disease” does. This applies to the case of depression (episode, severity, remission) and heart failure (systolic, diastolic, acute or chronic). When the health care model is a value-base system like a shar savings program, the accurate risk scores also create sensible spending targets; practices are never evaluate against sicker patients.
CMS-HCC V24 vs. V28: What Changed and Why
CMS-HCC V28 is the latest Medicare Advantage risk adjustment model. It supersed V24 in order to ensure payments are more in line with more recent fee-for-service cost data and to streamline what diagnoses affect payment. CMS rolled it out over 3 payment years, approximately one-third V28 in 2024, two-thirds in 2025, and 100% in payment year 2026.
Frequently Asked Questions
1. What does HCC stand for?
HCC stands for hierarchical condition category, a grouping of related diagnosis codes used to estimate patient risk.
2. What is a RAF score?
A risk adjustment factor (RAF) score is a number that reflects a patient’s expected healthcare costs, based on demographics and documented HCCs. A higher score means higher expected needs.
3. Does HCC coding apply to commercial insurance?
It applies mainly to Medicare Advantage, ACOs, and ACA plans. Traditional commercial plans often use different models.
4. How often must a diagnosis be documented?
Risk adjustment works on a calendar-year cycle, so chronic conditions should be assess and document at least once each year in a qualifying encounter.
5. What changed with CMS-HCC V28?
V28 expanded the number of categories, removed many diagnosis codes from payment and aligned diabetes weights. It has been fully phase in since 2026.
6. Can I code a condition from a problem list?
Not by itself. The condition needs evidence of monitoring, evaluation, assessment or treatment in the encounter.
7. Is HCC coding about increasing revenue?
No. Its purpose is to reflect patient complexity accurately. Coding conditions that are not support is a compliance risk.
8. Who can help with risk adjustment documentation?
Certified coders, clinical documentation improvement (CDI) specialists and billing partners with risk adjustment experience.
Disclaimer: This article is for educational purposes only. It is not compliance, legal or coding advice. Consult a qualified compliance professional or attorney about your specific situation.
