2026 ICD-10-CM Diagnosis Code E66.813Obesity, class 3

ICD-10-CM Codes›E00–E89›E65-E68›E66

ICD-10-CM E66.813
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E66.813 is a billable ICD-10-CM diagnosis code for obesity, class 3. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Obesity.

Code Identity

ICD-10-CM Code
E66.813
Billable Status
Yes — Valid for Submission
Code Describes
Obesity, class 3
Short Description
Obesity, class 3
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 CodeE66.813Obesity, class 3

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
        • 3

Clinical ClassificationClinical

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

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

Patient EducationClinical

Obesity

Obesity is a disease that means having too much body fat. It is different from being overweight, which means weighing too much. Both terms mean that your weight is greater than what's considered healthy for your height.

The full article covers:

  • What is obesity?
  • What raises your risk of obesity?
  • How is obesity diagnosed?
  • What health problems can obesity cause?
  • What are the treatments for obesity?

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement E66.813 replaces the following previously assigned code(s):

  • E66.01 - Morbid (severe) obesity due to excess calories
  • 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 E66.813Overview

Is E66.813 (Obesity class) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report obesity, class 3 on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E66.813 group to?

When obesity, class 3 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.

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.