E13 vs H20.0
E13 and H20.0 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 H20.0
iridocyclitis, iritis, uveitis (due to) (in) diabetes mellitus (E08-E13 with .39)
E13
Other specified diabetes mellitus
Not billable
- Chapter 4
- Endocrine, nutritional and metabolic diseases
- Section
- E08-E13
Use when the record says
- diabetes mellitus due to genetic defects of beta-cell function
- diabetes mellitus due to genetic defects in insulin action
- postpancreatectomy diabetes mellitus
- postprocedural diabetes mellitus
- secondary diabetes mellitus NEC
H20.0
Acute and subacute iridocyclitis
Not billable
- Chapter 7
- Diseases of the eye and adnexa
- Section
- H15-H22
Use when the record says
- Acute anterior uveitis
- Acute cyclitis
- Acute iritis
- Subacute anterior uveitis
- Subacute cyclitis
- Subacute iritis
Indexed under
- Iridocyclitis › acute
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