What is ICD-10 code B25.1?

B25.1 is the ICD-10-CM diagnosis code for Cytomegaloviral hepatitis. An infection of the liver caused by cytomegalovirus (CMV), typically occurring in patients with weakened immune systems. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B25.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B25.1 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. B25.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. B25.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for B25.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For B25.1, V28 maps to Opportunistic Infections at RAF 0.381 while V24 mapped to Opportunistic Infections at RAF 0.424. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting B25.1?

Document the presence of hepatitis and confirm CMV as the causative agent This condition is often associated with immunosuppression; consider coding related conditions Because B25.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM B25.1: Cytomegaloviral hepatitis

ICD-10-CM Code View

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Code lookupB25.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other viral diseases (B25-B34)

B25.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Cytomegaloviral hepatitis

An infection of the liver caused by cytomegalovirus (CMV), typically occurring in patients with weakened immune systems.

Buddy Insight

Cytomegaloviral hepatitis is liver inflammation caused by CMV infection, typically occurring in immunocompromised patients or occasionally in immunocompetent individuals with primary CMV infection.

CMS-HCC V28

Mapped

HCC 6

Opportunistic Infections

RAF 0.381

CMS-HCC V24

Mapped

HCC 6

Opportunistic Infections

RAF 0.424

ACA/HHS

Mapped

HCC 6

HHS-HCC 6

Varies by metal level

ESRD/PACE

Mapped

HCC 6

Opportunistic Infections

RAF 0.076

RXHCC

Mapped

HCC 5

Opportunistic Infections

RAF 0.468

Code Book Path

Official

B25Cytomegaloviral disease

B25.1Cytomegaloviral hepatitis

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for B25.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B25.1 in this effective period.

Related Child Codes

Official

B25.0Cytomegaloviral pneumonitis

B25.2Cytomegaloviral pancreatitis

B25.8Other cytomegaloviral diseases

B25.9Cytomegaloviral disease, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for B25.1 in this effective period.

Excludes 1

Official

congenital cytomegalovirus infection (P35.1)
cytomegaloviral mononucleosis (B27.1-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B25.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B25.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B25.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

CMV confirmed as the causative agent of hepatitis (CMV PCR, viral culture, or liver biopsy with CMV inclusions)

Liver function test abnormalities: elevated AST/ALT, bilirubin

Exclusion of other hepatitis causes (viral hepatitis A/B/C, drug-induced, autoimmune)

Underlying immunocompromised condition documented

MEAT Support

HCC Buddy guidance

CMV confirmed as the causative agent of hepatitis (CMV PCR, viral culture, or liver biopsy with CMV inclusions)

Liver function test abnormalities: elevated AST/ALT, bilirubin

Exclusion of other hepatitis causes (viral hepatitis A/B/C, drug-induced, autoimmune)

Underlying immunocompromised condition documented

Audit Caution

HCC Buddy guidance

Coding generic hepatitis when CMV is the confirmed causative agent — this loses the opportunistic infection HCC mapping

Not distinguishing CMV hepatitis from other causes of hepatitis in immunocompromised patients who may have multiple potential etiologies

Failing to code the underlying immunodeficiency that predisposed to CMV hepatitis

Using the unspecified CMV disease code (B25.9) when the liver is specifically documented as the affected organ

Common Mistakes

HCC Buddy guidance

B25.9 (Cytomegaloviral disease, unspecified) — Use B25.1 when liver involvement is specifically documented

B18.9 (Chronic viral hepatitis, unspecified) — Different viral etiology; CMV hepatitis is caused by cytomegalovirus, not hepatitis B or C

K75.9 (Inflammatory liver disease, unspecified) — Non-specific liver inflammation without identifying CMV as the cause

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is B25.1 an HCC code?

Yes. B25.1 (Cytomegaloviral hepatitis) maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections under V24), with a community non-dual aged RAF of 0.381. It is billable for payment year 2026.

Coder answer: B25.1 is billable and maps to V28 HCC 6, Opportunistic Infections. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: B25.1
Description: Cytomegaloviral hepatitis
HCC (V28): HCC 6 — Opportunistic Infections
RAF: 0.381
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 6, Opportunistic Infections

0.381

V24HCC 6, Opportunistic Infections

0.424

ESRDHCC 6, Opportunistic Infections

0.076

RxHCCHCC 5, Opportunistic Infections

0.468

Each model's RAF is its CMS base weight for that model's standard population, so 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 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.

Work B25.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B25.1

For B25.1to 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 B25.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B25.1 is the ICD-10-CM diagnosis code for cytomegaloviral hepatitis. An infection of the liver caused by cytomegalovirus (CMV), typically occurring in patients with weakened immune systems. B25.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other viral diseases (b25-b34).

Under the CMS-HCC V28 risk adjustment model, B25.1 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.381. Under the older V24 model, B25.1 mapped to the same category but with a base RAF weight of 0.424, 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.

Document the presence of hepatitis and confirm CMV as the causative agent. Because B25.1 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 B25.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the presence of hepatitis and confirm CMV as the causative agent
•This condition is often associated with immunosuppression; consider coding related conditions

Clinical Significance

Cytomegaloviral hepatitis is liver inflammation caused by CMV infection, typically occurring in immunocompromised patients or occasionally in immunocompetent individuals with primary CMV infection. As an opportunistic infection, it signals significant immune dysfunction and requires antiviral treatment.

Documentation Requirements

✓CMV confirmed as the causative agent of hepatitis (CMV PCR, viral culture, or liver biopsy with CMV inclusions)
✓Liver function test abnormalities: elevated AST/ALT, bilirubin
✓Exclusion of other hepatitis causes (viral hepatitis A/B/C, drug-induced, autoimmune)
✓Underlying immunocompromised condition documented
✓Treatment plan: antiviral therapy (ganciclovir/valganciclovir)

Commonly Confused Codes

•B25.9 (Cytomegaloviral disease, unspecified): Use B25.1 when liver involvement is specifically documented
•B18.9 (Chronic viral hepatitis, unspecified): Different viral etiology; CMV hepatitis is caused by cytomegalovirus, not hepatitis B or C
•K75.9 (Inflammatory liver disease, unspecified): Non-specific liver inflammation without identifying CMV as the cause