2026 ICD-10-CM Diagnosis Code E66.1Drug-induced obesity

ICD-10-CM Codes›E00–E89›E65-E68›E66

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

E66.1 is a billable ICD-10-CM diagnosis code for drug-induced obesity. 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 Drug induced or toxic related condition and Obesity.

Code Identity

ICD-10-CM Code
E66.1
Billable Status
Yes — Valid for Submission
Code Describes
Drug-induced obesity
Short Description
Drug-induced obesity
Same as the full description in the CMS dataset.
Parent Code
E66
Overweight and obesity

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE65-E68Overweight, obesity and other hyperalimentation
CategoryE66Overweight and obesity
This CodeE66.1Drug-induced obesity

Code EditsBilling

Medicare Code Editor checks that affect claim validity for E66.1.

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.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Drug-induced obesity

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Use Additional Code

  • code for adverse effect, if applicable, to identify drug T36 T50

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
      • drug-induced
    • Obesity
      • due to
        • drug

Clinical ClassificationClinical

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

CCSR INJ030
Drug induced or toxic related condition
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR END009
Obesity
Default principal diagnosis: inpatient No · outpatient No

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 E66.1 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 E66.1Overview

Is E66.1 (Overweight and obesity) a billable code?

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

What MS-DRG does E66.1 group to?

When drug-induced obesity 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 E66.1 justify an inpatient admission?

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

What is the ICD-9 equivalent of E66.1?

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

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.