Obesity vs. Morbid Obesity: ICD-10-CM Coding and Documentation Guidance

Obesity and morbid obesity are always clinically significant and reportable when documented by the provider. (Coding Clinic 4th Quarter 2018 p.77).

Definitions of Obesity and Morbid Obesity

According to the National Institute of Health the definition of morbid obesity is as follows:

• being 100 lbs or more above ideal body weight; or
• having a BMI of 40 or greater;
• having a BMI of 35 or greater with one or more obesity related health conditions such as hypertension, hyperlipidemia, diabetes mellitus, coronary artery disease, osteoarthritis, and gastroesophageal reflux disease.

BMI Classifications and Coding Rules

• BMI classifications (in kg/m2):
• Underweight- BMI <18.5
• Optimum range 18.5-24.9
• Overweight: BMI 25-29.9
• Class I Obesity: BMI 30-34.9
• Class II obesity: BMI 35-39.9\
• Class III obesity: BMI >40

BMI codes should only be assigned when there is an associated, reportable diagnosis (such as obesity). Do not assign BMI codes during pregnancy. 2024 ICD-10-CM Guidelines (I.C.21.c.3).

Clinical Indicators and Query Example

For example, a patient chart includes clinical indicators:

• Anthropometric flowsheet 01/01/23: Height: 167.7 cm., weight: 104 kg., BMI: 36.98
• 01/01/23 H&P- exam: “abdomen- obese”
• Risk Factors: DM II, HTN, hypercholesterolemia
• Treatment: daily weight, I&O, 60-75g CHO diet

A query should be considered to clarify the diagnosis of morbid obesity based on a BMI>35 with associated chronic comorbidities such as diabetes and heart disease.

Additional Coding Guidance for Obesity and BMI

• BMI codes must be accompanied by a weight-based diagnosis to be captured. BMI is a person’s weight in kilograms divided by height in meters squared. The BMI can be captured from clinicians who are not the patient’s provider such as a nurse, dietitian, or tech. However, the associated weight-based diagnosis must be documented by the patient’s physician. (Official Coding Guidelines, Section I.B.14; Documentation by Clinicians Other than the Patient’s Provider).
• If the provider documents overweight without additional documentation to support the clinical significance the code for overweight is not assigned. (Coding Clinic 4th Quarter 2018 p.77).
• Comorbidities do not change a diagnosis of obesity to morbid obesity. A query would be warranted if morbid obesity is not documented.
• If there is conflicting weight documentation between providers, defer to the attending physician.
• Class 3 obesity is synonymous with morbid obesity and is assigned code E66.01. Class 1 and 2 obesity need a query to determine the type or etiology if not specified in the documentation. (Coding Clinic 2^nd Quarter 2022 p.9).

Quality and Risk Adjustment Impact

Quality impact:

• Obesity is an Elixhauser variable
• E66.09, E66.1, E66.8, E66.9
• Morbid obesity is an HCC and an Elixhauser variable
• E66.01, E66.2
• BMI >30 to >70 is an Elixhauser variable and HCC
• Z68.30-Z68.45

Additional Clinical Context for Obesity

• 9% of the US adult population had class III obesity from 2017-2018.
• Factors increasing the risk for obesity include genetics, lack of physical activity, lack of sleep, high stress, increased age, female sex, hormone imbalances (hypothyroidism, high cortisol levels), cultural factors, exposure to chemicals such as obesogens, and low socioeconomic status
• A waist circumference in women of >35 or >40 inches in males may help to diagnose obesity.
• Treatment includes healthy lifestyle changes (exercise, diet), behavioral and psychological therapy, medications, and surgery.
• Obesity is associated with higher rates of death related to comorbidities such as diabetes, HTN, HLD, OSA, GERD, certain cancers, and PCOS.

Works Cited:

Bernard, S. P. (2019). Let’s get on the same page when coding BMI and obesity. AAPC Knowledge Center. Available at: https://www.aapc.com

Cleveland Clinic. (2023). Class III obesity (formerly known as morbid obesity): Causes, symptoms, risks & treatment. Available at: https://my.clevelandclinic.org

Abdelaal, M., le Roux, C. W., & Docherty, N. G. (2017). Morbidity and mortality associated with obesity. Annals of Translational Medicine, 5(7), 161. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5452220/