2026 ICD-10-CM Diagnosis Code E66.811Obesity, class 1

ICD-10-CM Codes›E00–E89›E65-E68›E66

ICD-10-CM E66.811
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E66.811 is a billable ICD-10-CM diagnosis code for obesity, class 1. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 640 through 641. The code is flagged as a questionable admission, since it rarely justifies inpatient admission on its own. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Obesity.

Code Identity

ICD-10-CM Code
E66.811
Billable Status
Yes — Valid for Submission
Code Describes
Obesity, class 1
Short Description
Obesity, class 1
Same as the full description in the CMS dataset.
Parent Code
E66.81
Obesity class

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE65-E68Overweight, obesity and other hyperalimentation
CategoryE66Overweight and obesity
This CodeE66.811Obesity, class 1

Code EditsBilling

Medicare Code Editor checks that affect claim validity for E66.811.

Questionable admission codes
Some diagnoses are not usually sufficient justification for admission to an acute care hospital. For example, if a patient is given code R030 for elevated blood pressure reading, without diagnosis of hypertension, then the patient would have a questionable admission, since elevated blood pressure reading is not normally sufficient justification for admission to a hospital. The following list contains diagnosis codes identified as questionable admission when used.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Obesity
      • class
        • 1

Clinical ClassificationClinical

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

CCSR END009
Obesity
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Understanding Adult Overweight & Obesity

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement E66.811 replaces the following previously assigned code(s):

  • E66.8 - Other obesity
FY 2025AddedAdded to the ICD-10-CM code setEffective October 1, 2024.
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E66.811Overview

Is E66.811 (Obesity class) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report obesity, class 1 on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E66.811 group to?

When obesity, class 1 is the principal diagnosis on an inpatient stay, it groups to MS-DRG 640, 641, with relative weights from 0.7782 to 1.3356 depending on complications. Higher weights mean higher Medicare reimbursement.

Does E66.811 justify an inpatient admission?

Not on its own. The Medicare Code Editor lists this code as a questionable admission because obesity, class 1 is not usually sufficient justification for admission to an acute care hospital.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.