Excludes1 pair

F51.8 vs G47.5-

F51.8 and G47.5 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.

The official note, declared on G47.5
parasomnia not due to a substance or known physiological condition (F51.8)
F51.8

Other sleep disorders not due to a substance or known physiological condition

Billable
Chapter 5
Mental, Behavioral and Neurodevelopmental disorders
Section
F50-F59
Indexed under
  • Parasomnia › nonorganic origin
  • Disorder › sleep › nonorganic › specified NEC
G47.5

Parasomnia

Not billable
Chapter 6
Diseases of the nervous system
Section
G40-G47

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