| OM Grade | Description |
| Grade 0 | Normal oral mucosa |
| Grade 1 | Soreness/erythema |
| Grade 2 | Soreness/erythema + ulceration + solid foods |
| Grade 3 | Soreness/erythema + ulceration + liquid diet only |
| Grade 4 | Soreness/erythema + ulceration + oral alimentation impossible |