C93 vs Z85.6
C93 and Z85.6 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 C93
personal history of leukemia (Z85.6)
C93
Monocytic leukemia
Not billable
- Chapter 2
- Neoplasms
- Section
- C81-C96
Use when the record says
- monocytoid leukemia
Z85.6
Personal history of leukemia
Billable
- Chapter 21
- Factors influencing health status and contact with health services
- Section
- Z77-Z99
Use when the record says
- Conditions classifiable to C91-C95
Indexed under
- History › personal › leukemia
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