ICD-10-CM 2027
ICD-10 code for mouth sore
From the official ICD-10-CM alphabetic index entry “Sore › mouth”. Page updated September 29, 2026.
About coding mouth sore
The ICD-10-CM code for mouth sore is K13.79 (Other lesions of oral mucosa). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on K13.79.
Within K13.7, choose K13.79 (Other lesions of oral mucosa) only when documentation doesn't support a more specific option: unspecified lesions of oral mucosa (K13.70).
Use an additional code to identify: alcohol abuse and dependence (F10.-), exposure to environmental tobacco smoke (Z77.22), exposure to tobacco smoke in the perinatal period (P96.81), history of tobacco dependence (Z87.891), occupational exposure to environmental tobacco smoke (Z57.31) and 2 more.
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
More specific mouth sore codes (official index)
- canker K12.0 — Recurrent oral aphthae
Common questions about mouth sore ICD-10 codes
What is the ICD-10 code for mouth sore?
- K13.79 — Other lesions of oral mucosa. More specific codes apply when the documentation supports them: K12.0.
What is the ICD-10 code for canker mouth sore?
- K12.0 — Recurrent oral aphthae.
Is K13.79 billable?
- Yes. K13.79 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can K13.79 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict K13.79 as a principal diagnosis.
Is K13.79 a CC or MCC?
- No. K13.79 is neither a CC nor an MCC under MS-DRG v44.0.