J70.0 vs T66
J70.0 and T66 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 T66
radiation pneumonitis (J70.0)
J70.0
Acute pulmonary manifestations due to radiation
Billable
- Chapter 10
- Diseases of the respiratory system
- Section
- J60-J70
Use when the record says
- Radiation pneumonitis
Indexed under
- Pneumonia › radiation (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Pneumonitis › radiation (acute) (primary)
- Poisoning › radiation (acute)
- Effect, adverse › radiationNOS › pneumonitis
- Inflammation, inflamed, inflammatory › respiratory, upper › acute, due to radiation (with exudation)
T66
Radiation sickness, unspecified
Not billable
- Chapter 19
- Injury, poisoning and certain other consequences of external causes
- Section
- T66-T78
Indexed under
- Irradiation effects, adverse
- Effect, adverse › infraredNOS
- Effect, adverse › radiationNOS
- Effect, adverse › ultravioletNOS
- Radiation › effects NOS
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