ICD-10 Code K12.31 – Oral mucositis (ulcerative) due to antineoplastic therapy (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K12.31 – Oral mucositis (ulcerative) due to antineoplastic therapy
What it is
K12.31 identifies ulcerative inflammation of the oral mucosa caused by antineoplastic therapy. Use it when chemotherapy, radiation, or other cancer treatment has led to painful mouth sores or ulceration.
Clinical signs
Typical findings include erythema, mucosal ulceration, soreness, and difficulty eating or speaking. Clinical features vary; refer to documentation for the specific site, severity, and treatment-related cause.
When to use this code
Use this code when the record clearly links oral mucositis to antineoplastic therapy. It fits documentation of chemotherapy-related mouth ulcers, radiation-associated oral injury, or treatment-induced stomatitis with ulceration. Code it only when the provider states the causal relationship.
Do not use for
Do not use K12.31 for oral ulcers without a documented antineoplastic cause. Also avoid it for nonulcerative mouth irritation or mucositis from other causes; check documentation.
Coding tip
Look for explicit wording such as “due to chemotherapy” or “due to antineoplastic therapy” before assigning K12.31.