What is ICD-10 code A40.0?

A40.0 is the ICD-10-CM diagnosis code for Sepsis due to streptococcus, group A. A serious bloodstream infection caused by Group A Streptococcus bacteria that can spread throughout the body and cause organ failure. This is a life-threatening condition requiring immediate medical treatment. A40.0 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. A40.0 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. A40.0 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. A40.0 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.

Which HCC does A40.0 map to under V28?

A40.0 maps to CMS-HCC V28 2 (Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does A40.0 pay in RAF?

A40.0 carries a community, non-dual, aged (CNA) RAF weight of 0.500 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for A40.0?

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 A40.0, 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 documentation supports A40.0?

Always verify the organism identification (Group A Streptococcus) is documented in the medical record before assigning this code Remember that sepsis codes require a secondary code for the associated organ dysfunction (SIRS criteria) and may require additional codes for the source of infection if documented Because A40.0 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. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM A40.0: Sepsis due to streptococcus

A40.0 maps to CMS-HCC V28 2 (RAF 0.500). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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Code lookupA40.0Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

A40.0

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

Sepsis due to streptococcus, group A

A serious bloodstream infection caused by Group A Streptococcus bacteria that can spread throughout the body and cause organ failure. This is a life-threatening condition requiring immediate medical treatment.

Buddy Insight

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

A40Streptococcal sepsis

A40.0Sepsis due to streptococcus, group A

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for A40.0 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A40.0 in this effective period.

Related Child Codes

Official

A40.1Sepsis due to streptococcus, group B

A40.3Sepsis due to Streptococcus pneumoniae

A40.8Other streptococcal sepsis

A40.9Streptococcal sepsis, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for A40.0 in this effective period.

Excludes 1

Official

neonatal (P36.0-P36.1)
puerperal sepsis (O85)
sepsis due to Streptococcus, group D (A41.81)

Code First

Official

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

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A40.0 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A40.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Blood cultures positive for Group A Streptococcus (S. pyogenes) or clinical sepsis with identified GAS source

Sepsis criteria met: documented infection with systemic inflammatory response

Source of infection identified (pharyngitis, cellulitis, necrotizing fasciitis, puerperal infection)

Severity indicators: organ dysfunction, hemodynamic status, vasopressor requirements

MEAT Support

HCC Buddy guidance

Blood cultures positive for Group A Streptococcus (S. pyogenes) or clinical sepsis with identified GAS source

Sepsis criteria met: documented infection with systemic inflammatory response

Source of infection identified (pharyngitis, cellulitis, necrotizing fasciitis, puerperal infection)

Severity indicators: organ dysfunction, hemodynamic status, vasopressor requirements

Audit Caution

HCC Buddy guidance

If necrotizing fasciitis is present, code M72.6 in addition to A40.0 — the sepsis code does not capture the soft tissue complication

Streptococcal toxic shock syndrome (A48.3) should be coded as a separate diagnosis when documented alongside GAS sepsis

Always add R65.20/R65.21 for severe sepsis or septic shock — these are not included in A40.0

In puerperal sepsis, consider whether O85 (Puerperal sepsis) is more appropriate as the principal diagnosis with A40.0 as additional

Common Mistakes

HCC Buddy guidance

A40.1 (Sepsis due to Streptococcus, group B) — Group B Strep typically affects neonates and peripartum women; Group A causes pharyngitis-related and skin/soft tissue sepsis

A40.9 (Streptococcal sepsis, unspecified) — Use A40.0 when Group A is specifically identified; do not default to unspecified

A41.9 (Sepsis, unspecified organism) — Use A40.0 when Strep Group A is the identified organism

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 A40.0 an HCC code?

Yes. A40.0 (Sepsis due to streptococcus, group A) 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: A40.0 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: A40.0
Description: Sepsis due to streptococcus, group A
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 A40.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for A40.0

For A40.0 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 A40.0 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

A40.0 is the ICD-10-CM diagnosis code for sepsis due to streptococcus, group a. A serious bloodstream infection caused by Group A Streptococcus bacteria that can spread throughout the body and cause organ failure. This is a life-threatening condition requiring immediate medical treatment. A40.0 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, A40.0 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, A40.0 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.

Always verify the organism identification (Group A Streptococcus) is documented in the medical record before assigning this code. Because A40.0 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 A40.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Always verify the organism identification (Group A Streptococcus) is documented in the medical record before assigning this code
•Remember that sepsis codes require a secondary code for the associated organ dysfunction (SIRS criteria) and may require additional codes for the source of infection if documented

Clinical Significance

Sepsis due to Group A Streptococcus (Streptococcus pyogenes) is an aggressive, rapidly progressive bloodstream infection associated with necrotizing fasciitis, streptococcal toxic shock syndrome, and high mortality. Group A Streptococcal sepsis requires urgent source control, high-dose penicillin, and often clindamycin for toxin suppression.

Documentation Requirements

✓Blood cultures positive for Group A Streptococcus (S. pyogenes) or clinical sepsis with identified GAS source
✓Sepsis criteria met: documented infection with systemic inflammatory response
✓Source of infection identified (pharyngitis, cellulitis, necrotizing fasciitis, puerperal infection)
✓Severity indicators: organ dysfunction, hemodynamic status, vasopressor requirements
✓Complications documented: necrotizing fasciitis, streptococcal toxic shock syndrome, if present

Commonly Confused Codes

•A40.1 (Sepsis due to Streptococcus, group B): Group B Strep typically affects neonates and peripartum women; Group A causes pharyngitis-related and skin/soft tissue sepsis
•A40.9 (Streptococcal sepsis, unspecified): Use A40.0 when Group A is specifically identified; do not default to unspecified
•A41.9 (Sepsis, unspecified organism): Use A40.0 when Strep Group A is the identified organism