Adult Morbid (severe) Obesity | August 2021 | Clinical Corner

August 1, 2021

Adult Morbid (Severe) Obesity

For adults 20 years and older, severe obesity has increased from 2.8% in years 1988 – 1994 to 9.2% in years 2017 – 2018 (1). Obesity-related conditions include heart disease, stroke, type 2 diabetes, sleep apnea, osteoarthritis, depression, hypertension and certain cancers like endometrial cancer, gastric cancer, colorectal cancer. The estimated annual health care costs of obesity-related illness are a staggering $190.2 billion, and that is a conservative estimate. (2) The Los Angeles Times in 2014 indicated that extreme obesity cut average life span extremely; a BMI above 40 has a life span reduction of 6.5 years to 14 years.

Obesity and its severity are classified using various characteristics like BMI, waist circumference and overall medical risk. Determining the correct terminology to use in diagnosis and documentation may be confusing because of the institutional (CDC, NIH, ICD 10) descriptive differences.

The diagnosis of morbid obesity (E66.01) or severe obesity (E66.01) is clinically significant and should be reported. The assignment of a diagnosis code is based on the provider’s diagnostic statement that the condition exists. (3) BMI codes need to be supported as medically relevant by an associated, reportable diagnosis. BMI codes were never intended to be used as a primary or standalone code.

What qualifies as morbid (severe) obesity:


  • Adult BMI is equal to or greater than 40 or
  • Adult BMI is equal to or greater than 35 and with at least one clinically significant and related comorbidity such as diabetes, hypertension, or sleep apnea


As a consideration when assessing morbid obesity, the BMI (body mass index) value is a screening tool (a mathematical calculation based on height and weight). Always report BMI documented with other weight-related diagnosis. However, the BMI may be coded alone without a weight-related diagnosis when the BMI has clinical significance for disorders like diabetes or hypertension and has an impact on quality scores and risk adjustment. The more recent guidelines suggest not assigning BMI codes during pregnancy but may use a billable diagnosis code O99.210 to specify a medical diagnosis of obesity complicating pregnancy, unspecified trimester.

Co-morbidities do not change a documented diagnosis of obesity into morbid obesity, these co-morbid conditions should be documented in the medical record and supported by ICD-10-CM coding.

In conclusion, providers must document a descriptive diagnostic term to express the clinical significance of a patient’s BMI. Morbid obesity is a BMI of 40 or more, severe obesity is a BMI of 35 to 39.9 plus at least one significant related comorbidity – both are assigned the same ICD-10-CM code of E66.01 which map to HCC (hierarchical coding category) 22 and increase the Risk Adjustment Factor (RAF) by 0.250.


  1. Prevalence Of Overweight, Obesity, And Severe Obesity Among Adults Aged 20 And Over: United States, 1960-1962 Through 2017-2018; Cheryl D. Fryar, M.S.P.H., revised January 29/2021, U.S. National Center for Health Statistics.
  2. John Cawley, Chad Meyerhoefer, The medical care costs of obesity: An instrumental variables approach. Journal of Health Economics, Volume 31, Issue 1, January 2012, pages 219-230.
  3. ACP Hospitalist; Richard Pinson M.D., FACP, October 2020.