R40Somnolence, stupor and coma

R40 is the ICD-10-CM diagnosis code for Somnolence, stupor and coma. It belongs to block R40-R46 (symptoms and signs involving cognition, perception, emotional state and behavior) and chapter 18 (symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified). It is a header code, so it can't be reported by itself; one of its 5 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: R40.0 (Somnolence), R40.1 (stupor), R40.2 (coma), R40.3 (state) and R40.4 (awareness).

Don't report R40 together with the conditions in its Excludes1 note: neonatal coma (P91.5), somnolence, stupor and coma in diabetes (E08-E13), somnolence, stupor and coma in hepatic failure (K72.-) and somnolence, stupor and coma in hypoglycemia (nondiabetic) (E15).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.