E66 vs R63.5
E66 and R63.5 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on R63.5
obesity (E66.-)
E66
Overweight and obesity
Not billable
- Chapter 4
- Endocrine, nutritional and metabolic diseases
- Section
- E65-E68
R63.5
Abnormal weight gain
Billable
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R50-R69
Indexed under
- Weight › gain
- Excess, excessive, excessively › weight › gain
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027