2027 ICD-10-CM Diagnosis Code A41.51Sepsis due to Escherichia coli [E. coli]

ICD-10-CM Codes›A00–B99›A30-A49›A41

ICD-10-CM A41.51
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A41.51 is a billable ICD-10-CM diagnosis code for sepsis due to Escherichia coli [E. coli]. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 791, 793, 870 through 872, 974 through 976. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 46 closely related codes. Coders also document this condition as sepsis caused by coliform bacteria. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Septicemia.

For Medicare Advantage risk adjustment, A41.51 maps to CMS-HCC Category 2 (Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock) under the V28 model, adding a risk factor of about 0.500 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
A41.51
Billable Status
Yes — Valid for Submission
Code Describes
Sepsis due to Escherichia coli [E. coli]
Short Description
Sepsis due to Escherichia coli [E. coli]
Same as the full description in the CMS dataset.
Parent Code
A41.5
Sepsis due to other Gram-negative organisms

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA41Other sepsis
This CodeA41.51Sepsis due to Escherichia coli [E. coli]

Medicare Risk Adjustment (HCC)Billing

A41.51 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 2— Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock
Payment HCC · PY 2027 one of 52 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.500
community, non-dual, aged · ranges 0.447–0.780 across segments
Hierarchy
Top of its hierarchy
HCC 2 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 2
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 2 · ESRD (V21): HCC 2 · ESRD (V24): HCC 2
ESRD V21 weights: 0.081 dialysis, 0.274–0.428 functioning graft · ESRD V24 weights: 0.087 dialysis, 0.270–0.532 functioning graft
Part D (RxHCC)
Not mapped
A41.51 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Sepsis caused by coliform bacteria
  • Sepsis caused by Escherichia coli

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A41.51: its own notes plus those printed at A41 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From A41 Other sepsis applies to 15 codes

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From A41 Other sepsis applies to 15 codes
  • 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)
  • sepsis (due to) (in) gonococcal (A54.86)
  • sepsis (due to) (in) herpesviral (B00.7)
  • sepsis (due to) (in) listerial (A32.7)
  • sepsis (due to) (in) melioidosis (A24.1)
  • sepsis (due to) (in) meningococcal (A39.2-A39.4)
  • sepsis (due to) (in) plague (A20.7)
  • sepsis (due to) (in) tularemia (A21.7)
  • toxic shock syndrome (A48.3)
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Code First

The underlying condition named in the note is sequenced before this code.

From A41 Other sepsis applies to 15 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A41.51, its category, or a range that includes it.

Code First 3

These codes say to code first a condition named in the note, and A41.51 is one of the conditions named.

  • I5A Non-ischemic myocardial injury (non-traumatic)
    sepsis (A41.-) names A41.-, which includes this code
  • N08 Glomerular disorders in diseases classified elsewhere
    sepsis (A40.0-A41.9) names A40.0-A41.9, which includes this code
  • N16 Renal tubulo-interstitial disorders in diseases classified elsewhere
    sepsis (A40.0-A41.9) names A40.0-A41.9, which includes this code

Use Additional Code 6

These codes say to use an additional code from the note, and A41.51 is one of the codes named.

  • J95.02 Infection of tracheostomy stoma
    sepsis (A40, A41.-) names A41.-, which includes this code
  • K94.02 Colostomy infection
    sepsis (A40.-, A41.-) names A41.-, which includes this code
  • K94.12 Enterostomy infection
    sepsis (A40.-, A41.-) names A41.-, which includes this code
  • K94.22 Gastrostomy infection
    sepsis (A40.-, A41.-) names A41.-, which includes this code
  • K95.01 Infection due to gastric band procedure
    sepsis (A40.-, A41.-) names A41.-, which includes this code
  • K95.81 Infection due to other bariatric procedure
    sepsis (A40.-, A41.-) names A41.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR INF002
Septicemia
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

E. coli Infections

E. coli is the name of a type of bacteria that lives in your intestines. Most types of E. coli are harmless. However, some types can make you sick and cause diarrhea. One type causes travelers' diarrhea. The worst type of E. coli causes bloody diarrhea, and can sometimes cause kidney failure and even death.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A41.51 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
038.42 E coli septicemia
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
995.91 Sepsis
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A41.51Overview

What is the ICD-10 code for sepsis due to Escherichia coli [E. coli]?

The ICD-10-CM code for sepsis due to Escherichia coli [E. coli] is A41.51 (sometimes written as A4151). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A41.51 (Sepsis due to other Gram-negative organisms) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report sepsis due to Escherichia coli [E. coli] on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does A41.51 group to?

When sepsis due to Escherichia coli [E. coli] is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 974, 976, 872, 975, 871, 870, with relative weights from 0.7879 to 6.9432 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A41.51 a CC or MCC?

CMS lists A41.51 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 46 closely related codes in its exclusion list.

Can A41.51 be reported with R78.81?

Not as a rule. The Excludes1 note at A41, which applies to A41.51, lists "bacteremia NOS (R78.81)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What HCC is A41.51?

A41.51 (sepsis due to Escherichia coli [E. coli]) maps to CMS-HCC Category 2 (Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock), commonly written as HCC 2, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 2 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.

Does A41.51 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, A41.51 adds a risk adjustment factor of about 0.500 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.447 to 0.780 depending on the payment segment). HCC 2 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 2 category page.