A41.9
BillableSepsis, unspecified organism
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A41.9 an HCC code?
Yes. A41.9 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 A41.9
For A41.9 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 A41.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A41.9 is the ICD-10-CM diagnosis code for sepsis, unspecified organism. A serious bloodstream infection where harmful bacteria or other organisms have entered the blood and are causing a severe systemic response, but the specific organism causing the infection has not been identified. This is a life-threatening condition where the body's response to infection causes organ dysfunction. A41.9 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, A41.9 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 A41.9 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.
Only use A41.9 when the organism is truly unknown or unspecified; if any organism is identified, use the more specific A41.x code (such as A41.0 for Staphylococcus aureus or A41.1 for Streptococcus pneumoniae). Because A41.9 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 A41.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Only use A41.9 when the organism is truly unknown or unspecified; if any organism is identified, use the more specific A41.x code (such as A41.0 for Staphylococcus aureus or A41.1 for Streptococcus pneumoniae)
- •Sepsis coding requires documentation of the systemic inflammatory response; ensure the clinical record supports sepsis diagnosis and consider querying the provider if only bacteremia or infection is documented without sepsis criteria
Clinical Significance
Sepsis, unspecified organism, is used when sepsis is clinically diagnosed and documented but the causative organism is unknown or not identified through cultures. While it captures the sepsis diagnosis for risk adjustment, it represents the lowest specificity level and should be updated when organism identification becomes available.
Documentation Requirements
- ✓Clinical documentation of sepsis with systemic inflammatory response criteria met
- ✓Blood cultures drawn (even if negative or pending)
- ✓Documentation of presumed source of infection
- ✓Organ dysfunction assessment (renal, hepatic, respiratory, coagulopathy, altered mental status)
- ✓Antibiotic therapy initiated (reflects clinical judgment of sepsis even without positive cultures)
Commonly Confused Codes
- •R65.20 (Severe sepsis without septic shock) — R65.20 is an additional code for severity, NOT a replacement for A41.9; use both when severe sepsis is present
- •R65.21 (Severe sepsis with septic shock) — Same as above — always pair with a sepsis code like A41.9
- •A40/A41.0-A41.89 — Any organism-specific sepsis code is preferred over A41.9 when the organism is known