ICD-10-CM > N00-N99 > N80-N98 > N91 N91 Absent, scanty and rare menstruation Non-Billable/Non-Specific Type 1 Excludes ovarian dysfunction (E28.-) Codes N91.0Primary amenorrheaN91.1Secondary amenorrheaN91.2Amenorrhea, unspecifiedN91.3Primary oligomenorrheaN91.4Secondary oligomenorrheaN91.5Oligomenorrhea, unspecified