Classification of disease severity in ulcerative colitis. Adapted from Truelove and Witts' criteria.
| Disease severity | Characteristics |
| Mild | <4 stools/day +/− blood, normal ESR, no signs of toxicity |
| Moderate | 4–6 stools/day, occasional blood, minimal signs of toxicity, CRP ≤30 mg/L |
| Severe | ≥6 bloody stools/day AND any of: |
| > temperature >37.8°C | |
| > tachycardia >90 bpm> | |
| > anaemia, Hb <105 g/L | |
| > ESR >30 mm/h, CRP >30 mg/L | |
| Fulminant | 10 stools/day, continuous bleeding, toxicity, abdominal tenderness or distention, transfusion requirement, colonic dilatation on X-ray |
CRP = C-reative protein; ESR = erythrocyte sedimentation rate; Hb = haemoglobin.