Ulcerative colitis (UC) is a disease that causes swelling and sores — called ulcers — in the lining of the rectum and large intestine. It is one type of inflammatory bowel disease (IBD), a group of conditions that cause long-term irritation in the gut. UC can start at any age, but it usually begins between ages 15 and 30, and it tends to run in families. The most common symptoms are belly pain and blood or pus in diarrhea. Other symptoms can include severe tiredness, weight loss, loss of appetite, bleeding from the rectum, joint pain, and sores on the skin. About half of people with UC have mild symptoms. Doctors use blood tests, stool tests, colonoscopy (a test that looks inside the large intestine with a small camera), and imaging tests to diagnose UC. Several types of drugs can help control it. Some people have long periods of remission — times when they are free of symptoms. Your care team can walk you through what all of this means for you.