In case you missed it: New ICD-10-CM codes for obesity classes

As of Oct. 1, 2024, an important ICD-10-CM obesity coding update introduced new obesity ICD-10 codes that identify specific obesity classes. The new ICD-10-CM codes allow healthcare organizations to capture Class 1 obesity, Class 2 obesity and Class 3 obesity with greater clinical specificity, supporting more accurate reporting, analytics and disease tracking. For coding professionals, understanding these new codes for obesity and the related obesity coding guidelines is essential to assigning the most appropriate diagnosis code. 

According to the Centers for Disease Control and Prevention (CDC), the standard BMI obesity classification categories for adults are: 

• E66.811 obesity class 1: BMI of 30 to less than 35
• E66.812 obesity class 2: BMI of 35 to less than 40
• E66.813 obesity class 3: BMI of 40 or greater 

These new classifications provide additional specificity beyond previous documentation of overweight and obesity, helping organizations better classify patient populations and monitor long-term health trends. 

Obesity is recognized as a chronic disease characterized by excess body fat accumulation. Research from the CDC shows that obesity increases the risk of multiple serious health conditions, including cardiovascular disease, diabetes, sleep apnea, respiratory complications and high blood pressure. Improved documentation of obesity classes may support better population health analysis and improve understanding of obesity-related outcomes across healthcare settings. 

For organizations involved in obesity risk adjustment coding, understanding the HCC impact of these new diagnoses is particularly important. For HCC obesity coding, the new E66.811 obesity class 1 and E66.812 obesity class 2 codes do not risk adjust in payment models, while E66.01 (Morbid obesity) and E66.813 obesity class 3 continue to carry risk-adjustment implications. Coding teams should ensure providers understand the distinction between obesity classifications and morbid obesity to support accurate documentation and reporting. 
 

Obesity documentation requirements

As organizations implement this ICD-10-CM obesity coding update, provider education becomes increasingly important. Accurate code assignment relies on clear clinical documentation that supports the diagnosis and obesity classification being reported. Effective obesity documentation requirements include: 

• Documenting the specific obesity class when clinically supported.
• Using terminology that aligns with current obesity coding guidelines.
• Clearly distinguishing between Class 3 obesity and morbid obesity when applicable.
• Supporting diagnoses with appropriate clinical evaluation and documentation. 

Strong documentation practices help coding professionals assign the most specific diagnosis code available and improve consistency across organizations. 
 

Common challenges when coding obesity classes 

When assigning the new obesity ICD-10 codes, coding teams should watch for several common challenges:

• Applying E66.01 when Class 3 obesity has been specifically documented.
• Assuming BMI alone determines code assignment without provider documentation.
• Confusing "severe obesity" or "morbid obesity" when documented with class of obesity.
• Overlooking the risk-adjustment differences between obesity classifications.
• Continuing to use historical coding interpretations after the latest ICD-10-CM obesity coding update. 
   

Important updates for coders and clinicians 

Heads up #1: In the second quarter of 2022, Coding Clinic advised capturing the diagnosis of Class 3 Obesity as E66.01, Morbid (severe) obesity due to excess calories. Class 1 and Class 2 required clarification from the provider. With the new codes, you should now code the specific class to the correct and most specific ICD-10-CM code. Note that for HCC risk adjustment coders, the new E66.811, Obesity, Class 1 and E66.812, Obesity, Class 2 codes do not risk adjust to a payment model, unlike E66.01, Morbid obesity and E66.813, Obesity, Class 3. This change may significantly impact coding practices if providers frequently document Class 1 or Class 2 obesity as severe, as you will no longer code “severe” obesity to E66.01 in 2025.

Heads up #2: Clinical terminology can be confusing. “Severe obesity” is often used synonymously with both Class 3 obesity and morbid obesity. To complicate matters further, the BMI index for Class 3 obesity starts at 40 kg/m²*, the same as for morbid obesity. The key takeaway is that when Class 3 obesity is documented, coders should assign the new E66.813, Obesity, Class 3. When “severe” obesity is documented without further specificity, coders should index and assign E66.01, Morbid (severe) obesity. As of April 1, 2025, the Official Coding Guidelines have been updated that if both “Class 3 obesity and morbid obesity are documented, only a code for Class 3 obesity should be assigned as it is more specific.”
 

Action steps for providers 

To avoid confusion and ensure accurate coding, providers should understand both the clinical and coding implications of the new obesity classes. Early education regarding documentation expectations, obesity coding guidelines and risk-adjustment considerations can help streamline coding workflows, improve data accuracy and support compliant reporting. Organizations that proactively address these changes will be better prepared for evolving documentation, quality and reimbursement requirements. 

*BMI reference can be found at CDC.gov Centers for Disease Control and Prevention and NIH.gov National Institute for Health.

Will Morriss, CCS, CCDS-O, is a senior coding analyst at Solventum.
Diane Pittman, CPC, CRC, CPMA, CCDS-O, is a senior clinical analyst at Solventum.