E66.01 Morbid (severe) obesity due to excess calories

Billable ICD-10-CM code, FY2026.

Excludes1 (never code together)

• morbid (severe) obesity with alveolar hypoventilation (E66.2)

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-)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 48 — Morbid Obesity
• CMS-HCC V22: HCC 22 — Morbid Obesity
• ESRD V24: HCC 22

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• 278.01 Morbid obesity (approximate)

Code annotations containing back-references to E66.01

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 E66.01

• Obesity › due to › excess calories › morbid
• Obesity › due to › excess calories › severe
• Obesity › morbid
• Obesity › morbid › due to excess calories
• Obesity › severe

Nearby codes

• E66 Overweight and obesity
• E66.0 Obesity due to excess calories
• E66.01 Morbid (severe) obesity due to excess calories (this code)
• E66.09 Other obesity due to excess calories
• E66.1 Drug-induced obesity
• E66.2 Morbid (severe) obesity with alveolar hypoventilation
• E66.3 Overweight
• E66.8 Other obesity