What is ICD-10 code A41.9?

A41.9 is the ICD-10-CM diagnosis code for Sepsis, unspecified organism. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). A41.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. A41.9 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. A41.9 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. A41.9 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 A41.9?

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 A41.9, V28 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock at RAF 0.500 while V24 mapped to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock at RAF 0.352. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting A41.9?

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 Because A41.9 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 A41.9: Sepsis, unspecified organism

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupA41.9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)

A41.9

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

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.

Buddy Insight

Sepsis, unspecified organism, is used when sepsis is clinically diagnosed and documented but the causative organism is unknown or not identified through cultures.

CMS-HCC V28

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.500

CMS-HCC V24

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.352

ACA/HHS

Mapped

HCC 2

HHS-HCC 2

Varies by metal level

ESRD/PACE

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.087

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

A41Other sepsis

A41.9Sepsis, unspecified organism

Inclusion Terms

Official

Septicemia NOS

Excludes 2

Official

sepsis (due to) (in) actinomycotic (A42.7)
sepsis (due to) (in) anthrax (A22.7)
sepsis (due to) (in) candidal (B37.7)
sepsis (due to) (in) Erysipelothrix (A26.7)
sepsis (due to) (in) extraintestinal yersiniosis (A28.2)

Related Child Codes

Official

A41.0Sepsis due to Staphylococcus aureus

A41.1Sepsis due to other specified staphylococcus

A41.2Sepsis due to unspecified staphylococcus

A41.3Sepsis due to Hemophilus influenzae

A41.4Sepsis due to anaerobes

Includes

Official

ICD-10-CM does not list Includes notes for A41.9 in this effective period.

Excludes 1

Official

bacteremia NOS (R78.81)
neonatal (P36.-)
puerperal sepsis (O85)
streptococcal sepsis (A40.-)

Code First

Official

, if applicable, postprocedural sepsis (T81.44-)
sepsis due to central venous catheter (T80.211-)
sepsis during labor (O75.3)
sepsis following abortion, ectopic or molar pregnancy (O03.37, O03.87, O04.87, O07.37, O08.82)
sepsis following immunization (T88.0-)

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A41.9 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A41.9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

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)

MEAT Support

HCC Buddy guidance

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)

Audit Caution

HCC Buddy guidance

A41.9 should not be the final code when culture results are available — always update to organism-specific codes

SIRS without infection (R65.10/R65.11) is NOT sepsis — do not code A41.9 for non-infectious SIRS

'Urosepsis' is not accepted as a sepsis diagnosis — query the provider for clarification and code the specific UTI and sepsis separately

Negative blood cultures do not preclude sepsis coding — clinical sepsis can be coded with culture-negative disease if the provider documents sepsis

Common Mistakes

HCC Buddy guidance

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

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 A41.9 an HCC code?

Yes. A41.9 (Sepsis, unspecified organism) 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), with a community non-dual aged RAF of 0.500. It is billable for payment year 2026.

Coder answer: A41.9 is billable and maps to V28 HCC 2, Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: A41.9
Description: Sepsis, unspecified organism
HCC (V28): HCC 2 — Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock
RAF: 0.500
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 2, Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock

0.500

V24HCC 2, Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock

0.352

ESRDHCC 2, Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock

0.087

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 A41.9 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

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.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

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 0.500. Under the older V24 model, A41.9 mapped to the same category but with a base RAF weight of 0.352, 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.

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