Mayo Score Explained: What 0–3 Means in Ulcerative Colitis
Last Updated Jan 15, 2026
Colonoscopy reports for ulcerative colitis (UC) often include a Mayo endoscopic score, sometimes called the Mayo endoscopic subscore. This is a simple 0–3 rating of what the colon lining looks like during the exam. Because symptoms and inflammation do not always match perfectly, the Mayo score helps put a number on visible inflammation so results can be compared over time.
What 0–3 means on a colonoscopy report
The Mayo endoscopic score is based on the most inflamed area seen during the scope, not an average of the whole colon. It describes how the surface of the colon looks, including redness, bleeding, and ulcers. In plain terms, higher numbers usually mean more active inflammation.
Mayo 0 (inactive): normal-looking lining, no clear signs of active inflammation.
Mayo 1 (mild): mild redness, a less clear “vascular pattern” (the normal tiny blood vessels are harder to see), and mild “friability” (the lining may bleed a little when touched).
Mayo 2 (moderate): more intense redness, loss of the vascular pattern, clear friability, and erosions (small breaks on the surface).
Mayo 3 (severe): spontaneous bleeding and ulceration (deeper breaks in the lining). [1]
A few details can prevent confusion. First, the Mayo endoscopic score is different from the full Mayo score, which also includes symptoms like stool frequency and rectal bleeding. Second, biopsies can show microscopic inflammation that is not always obvious to the eye during colonoscopy, so the Mayo score is important, but it is not the whole story.
Why the Mayo score matters for remission goals (and why “0 vs 1” comes up)
In UC care, endoscopy is used not only for diagnosis, but also to understand how well inflammation is controlled. Many treatment goals are written around mucosal healing, meaning the colon lining looks healed. In the American College of Gastroenterology (ACG) clinical guideline, mucosal healing is defined as resolution of inflammatory changes, with a Mayo endoscopic subscore of 0 or 1, and reaching this target is associated with a better chance of sustained remission and fewer major outcomes like hospitalization or surgery. [2]
This approach connects to “treat-to-target,” where care teams track symptoms plus objective measures (such as endoscopy and biomarkers) and adjust plans when targets are not met. STRIDE-II (Selecting Therapeutic Targets in Inflammatory Bowel Disease) reaffirmed endoscopic healing as a long-term target in inflammatory bowel disease, including UC. [3]
People may also hear about endoscopic remission UC as “Mayo 0” only. That is because Mayo 0 and Mayo 1 are not always equal in outcomes. In one prospective study of people with UC who had mucosal healing (Mayo 0 or 1), those with Mayo 1 relapsed more often than those with Mayo 0 over the following months. [4]
When a report says “Mayo score 2 UC,” it generally signals ongoing visible inflammation (often including erosions), which can help explain why a care team might discuss closer monitoring or a change in the overall management plan. The number is best viewed as a shared language for severity, progress, and goals over time, rather than a grade of how someone “should” feel day to day.