E66.811 Obesity, class 1

Billable ICD-10-CM code, FY2026.

Applies from E66 Overweight and obesity

Excludes2 (not included here)

• adiposogenital dystrophy (E23.6)
• lipomatosis dolorosa [Dercum] (E88.2)
• lipomatosis NOS (E88.2)
• Prader-Willi syndrome (Q87.11)

Code first

• obesity complicating pregnancy, childbirth and the puerperium, if applicable (O99.21-)

Use additional code

• code to identify body mass index (BMI), if known, for adults (Z68.1-Z68.45) or pediatrics (Z68.5-)

MS-DRG index

Defines the logic of DRG(s) 640-641 in MDC 10.

Medicare Code Edits (MCE v43.1 (April 2026))

• Questionable admission: Some diagnoses are not usually sufficient justification for admission to an acute care hospital when reported as principal diagnosis.

Code annotations containing back-references to E66.811

Back-references to E66.8

• Code Also: Z15.2 Genetic susceptibility to obesity ("other obesity (E66.8-)")

Back-references to E66

• Use Additional: E88.81 Metabolic syndrome and other insulin resistance ("obesity (E66.-)")
• Use Additional: O99.21 Obesity complicating pregnancy, childbirth, and the puerperium ("code to identify the type of obesity (E66.-)")
• Type 1 Excludes: R63.5 Abnormal weight gain ("obesity (E66.-)")
• Code First: Z99.3 Dependence on wheelchair ("obesity (E66.-)")

Diagnosis Index entries for E66.811

• Obesity › class › 1

Nearby codes

• E66.1 Drug-induced obesity
• E66.2 Morbid (severe) obesity with alveolar hypoventilation
• E66.3 Overweight
• E66.8 Other obesity
• E66.81 Obesity class
• E66.811 Obesity, class 1 (this code)
• E66.812 Obesity, class 2
• E66.813 Obesity, class 3
• E66.89 Other obesity not elsewhere classified
• E66.9 Obesity, unspecified