What is ICD-10 code A40.1?

A40.1 is the ICD-10-CM diagnosis code for Sepsis due to streptococcus, group B. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). A40.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. A40.1 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. A40.1 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. A40.1 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 A40.1?

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 A40.1, V28 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock at RAF 0.455 while V24 mapped to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock at RAF 0.455. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting A40.1?

Always verify the documentation specifies Group B Streptococcus (not other streptococcal groups) and confirms sepsis diagnosis before assigning this code This code requires a secondary code for the site of infection or organ dysfunction (such as septic shock R65.21, acute kidney injury, or respiratory failure) to fully capture the clinical picture and severity Because A40.1 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.

A40.1: Sepsis due to streptococcus, group B — ICD-10 | Septicemia, Sepsis, Systemic Inflammatory

ICD-10-CM Code View

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

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

A40.1

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

Sepsis due to streptococcus, group B

This is a serious bloodstream infection caused by Group B Streptococcus bacteria, which can spread throughout the body and cause life-threatening complications. Group B Strep is commonly found in the digestive and reproductive tracts and can be particularly dangerous in newborns, pregnant women, and elderly patients.

Buddy Insight

CMS-HCC V28

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.455

CMS-HCC V24

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.455

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 2

Septicemia, Sepsis, Systemic ...

RAF 0.0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Code Book Path

Official

A40Streptococcal sepsis

A40.1Sepsis due to streptococcus, group B

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for A40.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A40.1 in this effective period.

Related Child Codes

Official

A40.0Sepsis due to streptococcus, group A

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 A40.1 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 A40.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A40.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Blood cultures positive for Group B Streptococcus or clinical sepsis with GBS identified from relevant source

Patient demographics and risk context (neonate, peripartum, elderly, diabetic, immunocompromised)

In neonates: timing of onset (early <7 days vs. late 7-90 days), maternal GBS colonization status, intrapartum antibiotic prophylaxis received or not

Sepsis severity assessment with organ dysfunction documentation

MEAT Support

HCC Buddy guidance

Blood cultures positive for Group B Streptococcus or clinical sepsis with GBS identified from relevant source

Patient demographics and risk context (neonate, peripartum, elderly, diabetic, immunocompromised)

In neonates: timing of onset (early <7 days vs. late 7-90 days), maternal GBS colonization status, intrapartum antibiotic prophylaxis received or not

Sepsis severity assessment with organ dysfunction documentation

Audit Caution

HCC Buddy guidance

Neonatal GBS sepsis uses P36.0, not A40.1 — do not use adult sepsis codes on newborn records

In postpartum patients, consider O85 (Puerperal sepsis) as principal diagnosis with A40.1 as the causal organism code

Code any concurrent meningitis (G00.2 for streptococcal meningitis) separately when documented

Always add R65.20/R65.21 for severe sepsis/septic shock in adult patients

Common Mistakes

HCC Buddy guidance

A40.0 (Sepsis due to Streptococcus, group A) — Group A causes different clinical syndromes (pharyngitis, necrotizing fasciitis); Group B is neonatal/peripartum-associated

P36.0 (Sepsis of newborn due to Streptococcus, group B) — For neonatal GBS sepsis, use P36.0, not A40.1 — the P codes are used on the newborn record

A40.9 (Streptococcal sepsis, unspecified) — Use A40.1 when GBS is identified; do not default to unspecified

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 A40.1 an HCC code?

Yes. A40.1 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

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

0.455

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

0.455

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

0.000

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.

Work A40.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for A40.1

For A40.1to 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 A40.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

A40.1 is the ICD-10-CM diagnosis code for sepsis due to streptococcus, group b. This is a serious bloodstream infection caused by Group B Streptococcus bacteria, which can spread throughout the body and cause life-threatening complications. Group B Strep is commonly found in the digestive and reproductive tracts and can be particularly dangerous in newborns, pregnant women, and elderly patients. A40.1 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, A40.1 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 A40.1 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.

Always verify the documentation specifies Group B Streptococcus (not other streptococcal groups) and confirms sepsis diagnosis before assigning this code. Because A40.1 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 A40.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Always verify the documentation specifies Group B Streptococcus (not other streptococcal groups) and confirms sepsis diagnosis before assigning this code
•This code requires a secondary code for the site of infection or organ dysfunction (such as septic shock R65.21, acute kidney injury, or respiratory failure) to fully capture the clinical picture and severity

Clinical Significance

Sepsis due to Group B Streptococcus (Streptococcus agalactiae) predominantly affects neonates (early and late-onset neonatal sepsis), pregnant/postpartum women, and elderly or immunocompromised adults. In neonates, it remains a leading cause of sepsis and meningitis despite universal prenatal screening, and in adults it is increasingly recognized as a cause of serious invasive disease.

Documentation Requirements

✓Blood cultures positive for Group B Streptococcus or clinical sepsis with GBS identified from relevant source
✓Patient demographics and risk context (neonate, peripartum, elderly, diabetic, immunocompromised)
✓In neonates: timing of onset (early <7 days vs. late 7-90 days), maternal GBS colonization status, intrapartum antibiotic prophylaxis received or not
✓Sepsis severity assessment with organ dysfunction documentation
✓Source of infection if identified (urinary tract, skin/soft tissue, endometritis, osteoarticular)

Commonly Confused Codes

•A40.0 (Sepsis due to Streptococcus, group A): Group A causes different clinical syndromes (pharyngitis, necrotizing fasciitis); Group B is neonatal/peripartum-associated
•P36.0 (Sepsis of newborn due to Streptococcus, group B): For neonatal GBS sepsis, use P36.0, not A40.1: the P codes are used on the newborn record
•A40.9 (Streptococcal sepsis, unspecified): Use A40.1 when GBS is identified; do not default to unspecified