A41.4
BillableSepsis due to anaerobes
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A41.4 an HCC code?
Yes. A41.4 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock under the CMS-HCC V28 risk adjustment model (and Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock 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 A41.4
For A41.4 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 A41.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A41.4 is the ICD-10-CM diagnosis code for sepsis due to anaerobes. This is a serious bloodstream infection caused by bacteria that grow without oxygen, which can develop from infections in the abdomen, pelvis, or other areas of the body. It represents a life-threatening condition where harmful bacteria have spread throughout the bloodstream. A41.4 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).
Under the CMS-HCC V28 risk adjustment model, A41.4 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock (HCC 2) with a community, non-dual, aged base RAF weight of 0.455. The V24 model used during the PY2024–PY2025 transition mapped A41.4 the same way and at the same RAF weight. 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.
Ensure the clinical documentation explicitly states 'sepsis' and identifies anaerobic organisms (such as Bacteroides, Clostridium, or Peptostreptococcus) to support this specific code selection. Because A41.4 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 A41.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure the clinical documentation explicitly states 'sepsis' and identifies anaerobic organisms (such as Bacteroides, Clostridium, or Peptostreptococcus) to support this specific code selection
- •Remember to assign an additional code for the source/site of infection if documented (e.g., intra-abdominal infection) and include a code for sepsis-related organ dysfunction (R65.2x) if present
Clinical Significance
Sepsis due to anaerobes represents bloodstream infection by obligate anaerobic bacteria (Bacteroides fragilis, Clostridium species, Fusobacterium, Peptostreptococcus). These infections typically arise from intra-abdominal, pelvic, or oropharyngeal sources and are frequently polymicrobial. Anaerobic sepsis requires specific antibiotic coverage (metronidazole, carbapenems, or piperacillin-tazobactam).
Documentation Requirements
- ✓Blood cultures growing anaerobic organisms (requires anaerobic culture bottles drawn and processed correctly)
- ✓Identification of the specific anaerobic organism when available
- ✓Source of infection documented (intra-abdominal abscess, perforated viscus, aspiration, pelvic infection)
- ✓Sepsis criteria met with organ dysfunction assessment
- ✓Antibiotic regimen covering anaerobic organisms documented
Excludes 1 — Do NOT code together
- gas gangrene (A48.0)