2026 ICD-10-CM Diagnosis Code E66.09Other obesity due to excess calories

ICD-10-CM Codes›E00–E89›E65-E68›E66

ICD-10-CM E66.09
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E66.09 is a billable ICD-10-CM diagnosis code for other obesity due to excess calories. 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
E66.09
Billable Status
Yes — Valid for Submission
Code Describes
Other obesity due to excess calories
Short Description
Other obesity due to excess calories
Same as the full description in the CMS dataset.
Parent Code
E66.0
Obesity due to excess calories

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE65-E68Overweight, obesity and other hyperalimentation
CategoryE66Overweight and obesity
This CodeE66.09Other obesity due to excess calories

Code EditsBilling

Medicare Code Editor checks that affect claim validity for E66.09.

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
      • due to
        • excess calories
    • Obesity
      • exogenous
    • Obesity
      • nutritional

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.

Convert E66.09 to ICD-9-CMHistory

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

ICD-9-CM
278.00 Obesity NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E66.09Overview

Is E66.09 (Obesity due to excess calories) a billable code?

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

What MS-DRG does E66.09 group to?

When other obesity due to excess calories 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 E66.09 justify an inpatient admission?

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

What is the ICD-9 equivalent of E66.09?

Under the General Equivalence Mappings, other obesity due to excess calories converts to ICD-9-CM 278.00 (obesity NOS). The mapping is approximate, so confirm the match fits the documentation.

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.