Are GLP-1s Safe if You Have Ulcerative Colitis (UC)?

Glucagon-like peptide-1 (GLP-1) medications like semaglutide and tirzepatide are among the most talked-about drugs for weight loss and type 2 diabetes. But as their popularity has grown, so have questions from people living with ulcerative colitis (UC): Can people with inflammatory bowel disease (IBD) safely use these medications, which directly affect the gut?

It’s a fair question, and one that’s being asked by many people within the IBD community, according to Alan Moss, MD, the chief scientific officer at the Crohn’s & Colitis Foundation and a professor of gastroenterology at Boston University's Chobanian and Avedisian School of Medicine.

“Based on current data, GLP-1s appear generally well tolerated in people with IBD, but we do not yet have large, long-term trials in people with UC, so I tell patients we should decide together, case by case, based on their disease activity, nutritional status, and other health conditions,” Dr. Moss says.

How GLP-1 Medications Work in the Gut

“These drugs slow gastric emptying, help people feel fuller longer, and can reduce overall food intake, which is why they may be effective for weight loss,” says Danielle Gaffen, RDN, the San Diego–based founder of Eat Well Crohn’s Colitis, which provides personalized nutrition counseling for people living with IBD and other digestive conditions.

While weight loss is part of the appeal of these medications, that can be complicated for people with UC. Weight in UC tends to be highly variable, Gaffen says.

Some people with UC struggle with unintentional weight loss during flares. But others may gain weight due to limited safe foods, reduced exercise because of symptoms, or medications that can increase appetite and cravings, like corticosteroids, Gaffen says. For them, GLP-1s may offer an additional tool for weight management that can be difficult to achieve through diet and exercise alone.

There’s also growing interest in how these medications may influence inflammation in the gut, which is a key driver of UC.

• A study published in 2023 found that GLP-1 medications may help reduce inflammation and strengthen the gut lining in people with UC, though it notes that most of the evidence so far comes from animal and lab-based studies, not large trials in people.

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• A review published in 2025 in the Journal of Crohn’s and Colitis suggests that GLP-1 medications have both metabolic and anti-inflammatory benefits for people with IBD, with early studies linking them to improved outcomes like fewer hospitalizations.

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• A large real-world study published in 2026 in the journal Inflammatory Bowel Diseases found that GLP-1 use in people with UC and Crohn’s disease was linked to lower rates of steroid use, hospitalization, and intestinal surgery. The researchers used the Mayo Clinic Platform, a healthcare database covering 8 million patients, to find about 580 people with IBD who had taken GLP-1 drugs. They note that their findings are observational and need confirmation in clinical trials.

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Even with these promising results, the research has a long way to go, Moss says. “I’d call the data intriguing but not yet practice changing,” he says.

Navigating GI Side Effects

GI upset can increase your risk of dehydration, which is already a concern in people with UC, Moss says. “For someone with UC, even mild fluid losses can worsen fatigue, dizziness, and kidney strain, and significant vomiting or diarrhea can also mask or aggravate a flare, so we watch hydration and electrolytes closely.”

This is why working with a registered dietitian who specializes in IBD can help, Gaffen says. An RD can keep an eye on your intake of protein and other nutrients, as well as your hydration and electrolyte balance. “While some people with UC can do well on these medications, it really requires a careful team-based approach,” Gaffen says. This step is important even in people with UC who are using GLP-1s for weight loss, especially during flares, when symptoms are at their worst.

Distinguishing Between a Drug Side Effect and a UC Flare

One of the trickiest parts of taking a GLP-1 for people with UC is determining whether new symptoms are due to the medication or the disease flaring. There are some clues to watch for, Gaffen says.

GLP-1 side effects can look like nausea, early fullness, and changes in bowel habits, such as diarrhea or constipation, especially when starting the medication or increasing the dose. During a flare, people with UC could also encounter stool frequency, urgency, abdominal pain, or blood or mucus in the stool, Gaffen says.

“It’s not always easy to distinguish between the two based on symptoms alone, especially in someone with active disease,” she says.

Moss tells his patients to contact their IBD care team if symptoms are persistent, are severe, or include rising urgency or a fever. In most cases, confirming whether it’s a flare and not drug side effects will require medical evaluation, such as blood work, stool tests like a fecal calprotectin test, or an endoscopy, he says.

Rare but Serious Risks

• Gastroparesis (delayed stomach emptying)
• Intestinal blockage
• Pancreatitis

For people with UC who have had surgeries, these risks may mean you need extra caution and closer monitoring

As with any medication, understanding the risks is especially important when you have UC, particularly for people with a history of strictures, surgery, or complex disease, Moss says.

Tips for Staying Safe

Starting a GLP-1 if you have UC is doable, but it should be a coordinated decision between you and your IBD care team.

If you and your gastroenterologist decide to move forward, a few strategies can help reduce the risk:

Start low and go slow. To start GLP-1 therapy as safely as possible, Moss recommends that people with UC begin with a “modest initial dose and increase it gradually,” he says, while staying in close contact with their care team to assess tolerance and side effects. Your healthcare provider can always adjust the type of medication and the dosage if needed, Gaffen says.

Build a supportive eating plan. Gaffen focuses on helping patients maintain adequate nutrition despite reduced appetite. That may include smaller, more frequent meals; prioritizing protein; and adjusting fat or fiber intake depending on symptoms. “I meet patients where they are by considering their symptoms, any changes in intake or tolerance, and overall clinical picture. I also provide nutrition strategies to help manage side effects,” Gaffen says.

Stay on top of hydration. Both experts say that people with UC should prioritize fluid intake, especially if nausea or diarrhea are present.

Know the red flags. “Pay attention to red flags like persistent vomiting, severe abdominal pain, signs of dehydration, and blood in the stool. That should prompt an urgent call or visit to your doctor,” Moss says.