B18.1
BillableChronic viral hepatitis B without delta-agent
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B18.1 an HCC code?
Yes. B18.1 maps to Chronic Hepatitis under the CMS-HCC V28 risk adjustment model (and Chronic Hepatitis 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 B18.1
For B18.1 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 B18.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B18.1 is the ICD-10-CM diagnosis code for chronic viral hepatitis b without delta-agent. A long-term hepatitis B infection without the delta virus, where the patient remains infected with hepatitis B virus. B18.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral hepatitis (b15-b19).
Under the CMS-HCC V28 risk adjustment model, B18.1 maps to Chronic Hepatitis (HCC 65) with a community, non-dual, aged base RAF weight of 0.472. Under the older V24 model, B18.1 mapped to the same category but with a base RAF weight of 0.245 — 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.
This is the most common chronic hepatitis B code when delta virus is not present. Because B18.1 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 B18.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is the most common chronic hepatitis B code when delta virus is not present
- •Document whether the patient is HBeAg positive or negative if available for clinical management
Clinical Significance
Chronic hepatitis B without delta-agent is the most common form of chronic hepatitis B, affecting approximately 250 million people worldwide. It carries risk of progression to cirrhosis and hepatocellular carcinoma, requiring long-term monitoring and potential antiviral therapy. Risk adjustment capture is essential for reflecting ongoing disease management needs.
Documentation Requirements
- ✓Positive hepatitis B surface antigen (HBsAg) for >6 months confirming chronicity
- ✓HBeAg status (positive or negative) documenting viral replication phase
- ✓Hepatitis B viral load (HBV DNA quantitative PCR)
- ✓Liver disease assessment: ALT levels, fibrosis staging, imaging for hepatocellular carcinoma surveillance
- ✓Delta virus testing performed and negative (confirming absence of coinfection)