Crohn's disease and ulcerative colitis are often mentioned together, and for good reason. Both are forms of inflammatory bowel disease (IBD), both can cause painful digestive symptoms, and both tend to flare and improve over time rather than follow a straight line. While they share a decent amount of overlap, they are not the same condition.
Understanding the difference matters because diagnosis, treatment, and long-term management can look a little different depending on which type of IBD a person has. It also matters because symptoms like diarrhea, abdominal pain, and blood in the stool can sometimes be mistaken for other digestive issues, which can delay getting the right care.
What is Crohn's disease?
Crohn's disease is a chronic inflammatory bowel disease that causes inflammation anywhere along the digestive tract. In most people, it affects the end of the small intestine and the beginning of the large intestine, but it can show up in different places, and even in multiple areas at once.
One of the key features of Crohn's is that the inflammation can extend into deeper layers of the bowel wall, not just the surface lining. That can increase the risk of complications such as strictures, fistulas, abscesses, and bowel obstruction over time. Crohn's can range from mild to severe, and symptoms may develop gradually or come on more suddenly. Many people also experience periods of remission, when symptoms ease or disappear for a time, followed by flares.
What is ulcerative colitis?
Ulcerative colitis is also a chronic inflammatory bowel disease, but it affects the large intestine differently. Instead of appearing anywhere in the digestive tract, ulcerative colitis causes inflammation and ulcers in the inner lining of the colon and rectum. Unlike Crohn's, ulcerative colitis is limited to the large intestine, and the inflammation typically affects the innermost lining rather than deeper layers of tissue.
Ulcerative colitis can begin gradually and worsen over time, although symptoms can also appear more suddenly. Like Crohn's disease, it often follows a pattern of flares and remission.
Symptoms of Crohn's disease and ulcerative colitis
Since both Crohn's disease and ulcerative colitis are forms of irritable bowel disease, the symptoms can look very similar at first.
Common symptoms of Crohn's disease include diarrhea, abdominal pain and cramping, fatigue, fever, blood in the stool, reduced appetite, and unintended weight loss. Some people also develop mouth sores or pain and drainage near the anus related to fistulas. In more severe cases, Crohn's can affect other parts of the body too, including the skin, liver, eyes, joints, or bile ducts.
Ulcerative colitis often causes diarrhea, rectal bleeding, or blood in the stool, abdominal cramping, urgency, and tenesmus (the feeling of needing to have a bowel movement even when the bowel is empty). Some people also pass mucus in the stool. Fatigue, fever, nausea, vomiting, and weight loss can happen as symptoms become more severe or involve more of the colon.
It's also worth noting that digestive symptoms aren't always straightforward. While Crohn's and ulcerative colitis are inflammatory bowel diseases, other gut issues can cause overlapping symptoms too. For example, some people confuse flare-related food triggers with broader digestive sensitivity.
Why Crohn's disease and ulcerative colitis may be confused
The reason Crohn's disease and ulcerative colitis get mixed up so often is simple: they share many of the same headline symptoms. Both can cause diarrhea, abdominal pain, blood in the stool, fatigue, weight loss, and periods of flare-ups followed by remission. Both are driven by chronic inflammation in the digestive tract, and both can affect more than digestion alone, sometimes leading to symptoms involving joints, skin, eyes, or general energy levels.
On top of that, the exact cause of either condition isn't fully understood. In both cases, researchers believe genes, abnormal immune responses, the gut microbiome, and environmental factors likely play a role. That overlap can make the two conditions sound nearly interchangeable to someone hearing about them for the first time.
This is also where conversations around the microbiome can become relevant. While gut bacteria don't provide a simple explanation for IBD, researchers continue to study how dysbiosis may influence inflammation and symptom patterns.
Crohn's vs ulcerative colitis: how they're diagnosed and treated
There isn't one single test that instantly confirms Crohn's disease or ulcerative colitis. Doctors usually diagnose both conditions by reviewing symptoms, taking a medical and family history, doing a physical exam, and ordering tests to look for inflammation, bleeding, anemia, infection, and structural changes in the digestive tract.
That often includes blood tests, stool tests, and endoscopic procedures such as a colonoscopy. In ulcerative colitis, doctors typically use endoscopy of the large intestine to confirm inflammation and determine how much of the colon is affected. In Crohn's disease, colonoscopy may also be used, but imaging such as CT scans, MRI, capsule endoscopy, or other specialized studies may be needed because Crohn's can affect deeper layers and areas beyond the colon.
Treatment for both conditions is focused on reducing inflammation, managing symptoms, preventing complications, and helping maintain remission. For Crohn's disease, that may include corticosteroids, immune-modifying medications, biologics, nutritional support, and in some cases, surgery. For ulcerative colitis, doctors also use anti-inflammatory medicines, immune-modifying drugs, biologics, and sometimes surgery, particularly if medications aren't controlling the disease or complications develop. The exact treatment plan depends on disease severity, location, complications, and how someone responds over time.
When to talk to a doctor — and how Evidation can help
Ongoing digestive symptoms are worth paying attention to, especially when they're persistent or worsening. It's a good idea to talk to a doctor if you have diarrhea lasting more than a couple of weeks, ongoing abdominal pain, blood in the stool, unexplained weight loss, persistent fatigue, fever, or changes in bowel habits that don't seem to resolve.
Using Evidation to streamline the health data you're already tracking can help set you up for a useful conversation with your doctor. When you download the app and connect your health data, you'll receive insights that can help you understand more about your health. Click here to get started with Evidation today.
