ICD-10 Code K12 – Stomatitis and related lesions (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K12 – Stomatitis and related lesions
What it is
K12 identifies inflammatory or ulcerative conditions of the mouth, including stomatitis and related oral lesions. Use it when the documentation describes nonspecific inflammation of oral tissues rather than a more specific diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include oral redness, swelling, soreness, ulcers, or painful mouth lesions that affect eating or speaking.
When to use this code
Use K12 when the provider documents stomatitis, oral mucositis, or related nonspecific lesions of the mouth and does not name a more specific cause. It is also appropriate when the record supports inflammation of oral mucosa without a better-defined diagnosis. Check documentation if the lesion is described as traumatic, infectious, or medication-related.
Do not use for
Do not use K12 for clearly identified conditions such as oral candidiasis, aphthous ulcers with a more specific code, or malignant oral lesions. If the note gives a different underlying diagnosis, code that condition instead.
Coding tip
Code K12 only when the chart supports a nonspecific mouth inflammation or lesion and no more specific oral diagnosis is documented.