Ulcerative colitis symptoms: what to look out for

Ulcerative colitis (UC) causes a range of symptoms that can vary significantly from person to person — and even from flare to flare in the same person. Understanding what to look for and what signals a need for urgent attention can help you have more productive conversations with your gastroenterologist.

The most common UC symptoms

Bloody diarrhea or blood in stool

Blood in the stool is one of the hallmark signs of UC. It happens because inflammation in the colon causes the lining to ulcerate and bleed. The blood may appear bright red (coming from lower in the colon) or mixed into the stool. Some people notice only small streaks; others experience significant bleeding during flares.

If you suddenly notice a large amount of blood, or bleeding that is new or worsening, contact your healthcare provider promptly. For a detailed guide, see our article on blood in stool with ulcerative colitis.

Urgent and frequent bowel movements

Many people with UC feel a sudden, strong urge to go — and may not be able to hold it. Urgency and frequency are among the most disruptive symptoms, often affecting work, social activities, and sleep. Some people need the bathroom 10 or more times a day during a severe flare.

Abdominal cramping and pain

Pain is usually felt in the lower left abdomen, though it can occur anywhere. Cramping often comes on just before a bowel movement and may ease slightly after going. During a flare, the pain can be constant and severe enough to interfere with daily activity.

Fatigue and low energy

Fatigue in UC is not just tiredness — it is a deep exhaustion that does not improve with rest. It is caused by the body’s inflammatory response, blood loss (leading to anemia), disrupted sleep, and the physical strain of frequent bathroom trips. Many patients describe fatigue as one of their most limiting symptoms.

Unintended weight loss

Ongoing inflammation, reduced appetite, and the body’s difficulty absorbing nutrients can lead to weight loss. Significant or rapid unintended weight loss should always be discussed with a doctor.

Feeling like the bowels never fully empty (tenesmus)

Tenesmus is the persistent sensation of needing to pass stool even when the bowel is empty. It is caused by inflammation and irritation in the rectum and can be uncomfortable and exhausting.

Night-time bathroom trips

Waking up during the night to use the bathroom is a common UC symptom during active disease. It is also a useful signal to share with your doctor — nocturnal symptoms often indicate significant inflammation.

Mild, moderate, and severe symptoms

Doctors typically categorize UC activity as mild, moderate, or severe based on:

• Mild: Fewer than four loose stools per day, small amounts of blood, no fever, and minimal impact on daily life
• Moderate: Four to six stools per day with blood, some abdominal pain and cramping, starting to affect daily activities
• Severe: More than six bloody stools per day, significant cramping, high fever, rapid heartbeat, and dehydration — this requires urgent medical attention

Symptoms beyond the gut (extraintestinal)

UC can cause symptoms outside the digestive tract, including:

• Joint pain — particularly in the large joints (knees, ankles, hips)
• Skin problems — rashes, tender red nodules, or sores around the mouth
• Eye inflammation — redness, pain, or blurred vision
• Liver problems — some people with UC develop primary sclerosing cholangitis (PSC), a liver condition
• Anemia — caused by blood loss and chronic inflammation

If you develop any of these alongside gut symptoms, let your gastroenterologist know.

How symptoms change over time

UC typically follows a pattern of flares (active symptoms) and remission (little or no symptoms). Remission can last for months or years. Some people have only one or two flares in their lifetime; others experience them frequently. Understanding what triggers a UC flare-up can help you respond earlier and protect your remission.

Keeping a symptom diary — tracking stool frequency, blood, pain levels, and energy — helps your doctor assess whether your disease is in remission, whether treatment is working, and whether a change in approach is needed.

Questions to ask your GI doctor

• How severe is my UC based on my current symptoms?
• Should I have blood tests or a colonoscopy to assess my disease activity?
• Are my current symptoms consistent with a flare — and what should I do?
• Are my medications adequately controlling my disease?
• What symptom changes would mean I need to call your office urgently?
• Should I be checked for anemia given the blood in my stool?
• Are any of my symptoms outside the gut related to my UC?

When to contact a doctor

Contact your healthcare provider if:

• You notice new blood in your stool
• Your symptoms are getting worse or not responding to treatment
• You are losing weight unintentionally
• You are waking at night with symptoms
• Fatigue is significantly affecting your daily life

Seek emergency care immediately if you have: heavy rectal bleeding, severe abdominal pain, high fever (above 38.5°C / 101.3°F), or signs of dehydration such as dizziness, rapid heartbeat, or inability to keep fluids down.

This content is for educational purposes only. It is not a substitute for advice from a licensed healthcare professional. Always consult your doctor about your specific symptoms.