The ICD-10-CM diagnosis code E66.01, titled “Morbid (severe) obesity due to excess calories,” is a critical code within the International Classification of Diseases, 10th Revision, Clinical Modification system. This code is used by healthcare professionals and medical coders in the United States to classify and document diagnoses related to morbid obesity stemming from excessive calorie intake. Understanding this code is crucial for accurate medical billing, statistical tracking, and healthcare management.
E66.01: A Billable and Specific Code
Specifically, E66.01 is designated as a billable/specific code. This means it is precise enough to be used for reimbursement purposes in healthcare claims. The code is part of the broader category E66, which encompasses “Overweight and obesity,” and the more specific subcategory E66.0, “Obesity due to excess calories.” E66.01 further pinpoints the diagnosis to morbid or severe obesity resulting from consuming more calories than the body expends.
Effective Date and International Variations
The 2025 edition of ICD-10-CM, which includes code E66.01, became effective on October 1, 2024. It’s important to note that this is the American ICD-10-CM version. International versions of ICD-10 for code E66.01 may differ, so accuracy requires using the appropriate coding system for the specific region.
Type 1 Excludes Note: What E66.01 Does Not Include
ICD-10-CM utilizes “excludes” notes to clarify coding guidelines. E66.01 has a Type 1 Excludes note, which is a “pure excludes.” This means that certain conditions should never be coded with E66.01 simultaneously. Type 1 excludes notes are used when two conditions are mutually exclusive, such as when one is a congenital form and the other is an acquired form of the same condition. While the original article doesn’t specify what is excluded for E66.01, in general, with obesity codes, it is crucial to check for specific excludes notes in the official ICD-10-CM guidelines to avoid coding errors.
Annotation Back-References and Synonyms
The E66.01 code is also associated with annotation back-references. These references point to other codes that may contain important notes relevant to E66.01. These annotations can include:
- Applicable To annotations
- Code Also annotations
- Code First annotations
- Excludes1 annotations
- Excludes2 annotations
- Includes annotations
- Note annotations
- Use Additional annotations
These back-references are valuable for ensuring comprehensive and accurate coding by directing coders to related information and guidelines within the ICD-10-CM system.
To further clarify the meaning of E66.01, several approximate synonyms are associated with this diagnosis code. These include:
- Morbid obesity
- Obesity (body mass index (BMI) more than 40)
- Obesity body mass index (BMI) >=40
- Obesity, body mass index (BMI 40-44.9)
- Obesity, body mass index (BMI) >= 70
- Obesity, body mass index (BMI) 45-49.9
- Obesity, body mass index (BMI) 50-59.9
- Obesity, body mass index (BMI) 60-69.9
- Obesity, body mass index (BMI) more than 99th percentile (for children)
- Severe adult obesity with BMI between 40-44.9, 45-49.9, and 50 to 59.9
- Severe childhood obesity with BMI >99th percentile
- Severe obesity
- Severe obesity in pregnancy
- Severely obese adult with body mass index
These synonyms highlight that E66.01 is used to classify cases of severe obesity, often defined by a BMI of 40 or greater in adults, or above the 99th percentile for children. The code also encompasses various ranges of very high BMIs, emphasizing the severity of the condition being coded.
Code History and Context within ICD-10-CM
The code E66.01 is relatively new within the ICD-10-CM system, with its first effective date in 2016 (October 1, 2015). Since then, there have been no changes to the code through the 2025 edition, indicating its continued relevance and stability within the diagnostic coding framework. E66.01 is positioned within the ICD-10-CM hierarchy under:
- Chapter IV: Endocrine, Nutritional and Metabolic Diseases (E00-E89)
- Diseases of Metabolism (E70-E88) (Note: While E66 is listed under E70-E88 in the original article’s “ICD-10-CM Codes Adjacent To E66.01” section, E66 actually falls under E65-E68 in the broader ICD-10-CM structure, which is more accurately “Disorders of nutrition, metabolism and immunity”)
- Overweight and Obesity (E65-E68)
- Obesity (E66)
- Obesity due to excess calories (E66.0)
Understanding this hierarchical structure helps to contextualize E66.01 within the larger system of medical diagnosis coding.
Conclusion
In summary, diagnosis code E66.01, Morbid (severe) obesity due to excess calories, is a specific and billable ICD-10-CM code essential for classifying and documenting severe obesity resulting from excessive calorie intake. Its detailed synonyms, annotation back-references, and placement within the ICD-10-CM system are all important for accurate medical coding, billing, and data analysis related to this significant health condition. Healthcare professionals and medical coders should utilize this code precisely according to official ICD-10-CM guidelines for effective healthcare management and reimbursement processes.
