ICD-10 Code K12.33 – Oral mucositis (ulcerative) due to radiation (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K12.33 – Oral mucositis (ulcerative) due to radiation
What it is
K12.33 identifies ulcerative inflammation of the oral mucosa caused by radiation therapy. Use it when documentation links painful mouth sores or mucosal breakdown directly to radiation exposure.
Clinical signs
Typical findings include erythema, ulceration, soreness, and difficulty eating or speaking. Clinical features vary; refer to documentation for the specific oral findings and the radiation cause.
When to use this code
Use K12.33 when the record clearly states oral mucositis is due to radiation, such as after head, neck, or oral cavity radiotherapy. You should code the documented condition, not a general stomatitis diagnosis, when radiation is the stated cause.
Do not use for
Do not use this code for mucositis from chemotherapy, infection, trauma, or unspecified stomatitis. Check documentation if the cause is not clearly radiation-related.
Coding tip
Verify that the provider documents both mucositis and radiation causation before assigning K12.33.