Flares & ER
Ulcerative colitis produces a range of symptoms that shift depending on how much of the colon is inflamed and how active the disease is at any given time. Understanding what each symptom signals about your disease can help you communicate more effectively with your gastroenterologist and recognize when something has changed. This guide breaks down the most common ulcerative colitis symptoms explained in terms of what they indicate about location, severity, and when they warrant a call to your care team.
Blood in Stool: What the Color and Amount Tell You
Rectal bleeding is one of the hallmark symptoms of UC, and blood in stool with ulcerative colitis appears in roughly 87% of patients at some point during their disease course. The blood is typically bright red because it originates from the lining of the colon and rectum, close to the point of exit. If you notice darker or maroon-colored blood, that may indicate inflammation higher in the colon or another source entirely, and it warrants prompt medical attention.
The amount of bleeding correlates directly with disease activity. According to Cleveland Clinic, mild UC may produce occasional streaks of blood on the stool or on toilet paper, while moderate to severe disease can result in visibly bloody stools with every bowel movement. If you are passing large amounts of blood, experiencing dizziness or lightheadedness, or seeing blood in more than six bowel movements per day, contact your GI team the same day. Those signs may indicate a severe flare requiring treatment escalation.
Mucus in Stool: A Sign of Active Inflammation
Mucus in stool with ulcerative colitis is a distinctive marker that separates active UC from many other digestive complaints. The colon naturally produces a thin layer of mucus to protect its lining, but when inflammation damages the tissue and creates ulcers, the body ramps up mucus production. The result is a visible, clear or whitish coating on the stool, sometimes appearing on its own without formed stool at all.
When that mucus takes on a yellowish or greenish color, it often contains pus, which signals that the ulcers have become infected or that the inflammation is more severe. The presence of pus mixed with mucus is a finding worth reporting to your gastroenterologist, especially if it represents a new change from your baseline. Tracking the consistency, color, and frequency of mucus output over time gives your care team a practical measure of how your disease is responding to treatment between scoping procedures.
Where Pain Shows Up and What It Means
The location of ulcerative colitis abdominal pain maps closely to the extent of your disease. UC almost always begins in the rectum and spreads continuously upward, so pain tends to follow that same path. Healthline reports that UC pain most commonly presents in the lower left abdomen, corresponding to the sigmoid and descending colon where left-sided colitis concentrates.
If your pain is limited to the rectal area or very low abdomen, that often indicates ulcerative proctitis, the mildest extent of disease. Left side pain from ulcerative colitis suggests the inflammation extends up through the descending colon. Pain that spreads across the entire lower abdomen or into the upper abdomen may indicate pancolitis, where the full colon is involved. Severe, sudden abdominal distension with pain is a potential sign of toxic megacolon, a medical emergency that requires immediate care.
Diarrhea Frequency as a Severity Indicator
The number of bowel movements per day is one of the primary clinical measures your gastroenterologist uses to assess disease activity. Standardized scales like the Mayo Score and the Truelove and Witts Index both incorporate stool frequency as a core component. The general thresholds are:
Mild UC: fewer than four bowel movements per day
Moderate UC: four to six bowel movements per day
Severe UC: more than six loose, bloody stools per day
These numbers matter because they give your doctor an objective way to track disease trajectory. If you have been averaging three bowel movements a day and that number climbs to six or more over the course of a week, that shift represents a meaningful change in disease activity even if each individual episode feels manageable. Consistent daily tracking is the most reliable way to catch an upward trend before it becomes a full flare.
Gas, Bloating, and Constipation: The Overlooked Symptoms
Ulcerative colitis gas and bloating receive less attention than bleeding or diarrhea, but they affect a significant number of patients. Research has found that people with UC often have elevated levels of hydrogen sulfide-producing gut bacteria, which contributes to excess gas and abdominal distension. Bloating can persist even during periods of relative remission, making it a frustrating symptom that does not always align with other markers of disease activity.
Ulcerative colitis constipation may sound contradictory, but it is more common than most patients expect. A study published in the Journal of Gastroenterology and Hepatology found that 46% of UC patients met criteria for proximal constipation, now termed ulcerative colitis-associated constipation syndrome. This pattern is especially common in ulcerative proctitis, where rectal inflammation triggers frequent urgency and mucus passage while stool higher in the colon moves sluggishly. You may feel the constant need to use the bathroom while only passing an actual formed stool once every few days.
When to Contact Your GI Between Appointments
Not every symptom shift requires a phone call, but certain changes should prompt same-day communication with your care team. Reach out if you notice:
A sudden increase to six or more bloody bowel movements in a 24-hour period
New or worsening fever above 100.4 F alongside GI symptoms
Severe abdominal pain or sudden distension that feels different from your typical cramping
Between those acute situations, the most useful thing you can do is maintain a consistent symptom record. Your gastroenterologist relies on patient-reported data to make treatment decisions between colonoscopies. When you can show exactly when your stool frequency increased, when blood appeared, or when pain shifted location, your provider can respond with more targeted adjustments.
Log your symptoms daily with Aidy to build a pattern your GI can use to assess your disease activity between colonoscopies.