N91Absent, scanty and rare menstruation
Code usage status
Primary diagnosis
Select a more specific code
Apply only when it matches the confirmed diagnosis and the documented clinical record.
Specificity
Do not use N91 directly
Use the most specific code supported by the record.
- Chapter XIV
- Diseases of the genitourinary system
- Group N80-N98
- Noninflammatory disorders of female genital tract
- Official Vietnamese name
- Vô kinh, thiểu kinh và/hoặc hiếm kinh
- Additional WHO coding guidance
- Excl.: ovarian dysfunction (E28.-)
Related N91 codes
N91.0
Primary diagnosis candidate
Primary amenorrhoea
N91.1
Primary diagnosis candidate
Secondary amenorrhoea
N91.2
Primary diagnosis candidate
Amenorrhoea, unspecified
N91.3
Primary diagnosis candidate
Primary oligomenorrhoea
N91.4
Primary diagnosis candidate
Secondary oligomenorrhoea
N91.5
Primary diagnosis candidate
Oligomenorrhoea, unspecified
Clinical record checklist
View coding guide →- Confirm that the code matches the final documented diagnosis.
- Use one primary-diagnosis code and record only relevant additional conditions.
- Review Ministry indicators, inclusions, exclusions and notes.
- Do not infer a diagnosis beyond the clinical record.
2026 regulatory basis
Indicators are taken from columns 24–29 of the classification accompanying Circular 06/2026/TT-BYT, cross-referenced with Decision 1849/QĐ-BYT and Official Dispatch 4059/BYT-BH.
