B18.1 ICD-10-CM Code: Chronic viral hepatitis B without delta-agent
B18.1 maps to CMS-HCC V28 65. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral hepatitis (B15-B19)
B18.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceChronic 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.
Buddy Insight
Chronic hepatitis B without delta-agent is the most common form of chronic hepatitis B, affecting approximately 250 million people worldwide.
CMS-HCC V28
MappedHCC 65
Coefficient HCC 65: 0.185 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 037_2
Code-level coefficient reference
ESRD/PACE
MappedHCC 29
Code-level coefficient reference
RXHCC
MappedHCC 56
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Carrier of viral hepatitis B
- Chronic (viral) hepatitis B
Excludes 2
Official- carrier or suspected carrier of infectious disease (Z22.-)Inherited from A00-B99, B15-B19
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)Inherited from A00-B99, B15-B19
- infectious and parasitic diseases specific to the perinatal period (P35-P39)Inherited from A00-B99, B15-B19
- influenza and other acute respiratory infections (J00-J22)Inherited from A00-B99, B15-B19
- cytomegaloviral hepatitis (B25.1)Inherited from A00-B99, B15-B19
- herpesviral [herpes simplex] hepatitis (B00.81)Inherited from A00-B99, B15-B19
Related Codes
Includes
Official- diseases generally recognized as communicable or transmissibleInherited from A00-B99, B18
- Carrier of viral hepatitisInherited from A00-B99, B18
Excludes 1
Official- certain localized infections - see body system-related chaptersInherited from A00-B99, B15-B19
- sequelae of viral hepatitis (B94.2)Inherited from A00-B99, B15-B19
Code First
OfficialNo Code First sequencing instructions are included in this display for B18.1. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify resistance to antimicrobial drugs (Z16.-)Inherited from A00-B99, B18
- code, if applicable, for ascites (R18.8)Inherited from A00-B99, B18
Code Also
OfficialNo Code Also instructions are included in this display for B18.1. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is B18.1 an HCC code?
Yes. B18.1 (Chronic viral hepatitis B without delta-agent) maps to HCC 65, Chronic Hepatitis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.185. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: B18.1 is billable and maps to V28 HCC 65, Chronic Hepatitis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- B18.1
- Description
- Chronic viral hepatitis B without delta-agent
- HCC (V28)
- HCC 65 — Chronic Hepatitis
- RAF reference coefficient
- 0.185
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work B18.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for B18.1
For B18.1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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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 source-labeled community, non-dual, aged reference coefficient of 0.185. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This is the most common chronic hepatitis B code when delta virus is not present. For B18.1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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)
Commonly Confused Codes
- •B18.0 (Chronic viral hepatitis B with delta-agent): Same hepatitis B but with delta virus coinfection; B18.1 specifically excludes delta
- •B16.9 (Acute hepatitis B without delta-agent and without hepatic coma): Acute infection, not chronic; must document >6 months duration for chronic
- •Z22.51 (Carrier of viral hepatitis B): Carrier status without active disease; B18.1 indicates active chronic infection