Ozempic (semaglutide) is a GLP-1 receptor agonist licensed in the UK for type 2 diabetes management, but many patients wonder about its effects on existing bowel conditions. Diverticulitis, an inflammatory condition affecting the colon, requires careful consideration when starting new medications that influence gastrointestinal function. Whilst Ozempic commonly causes gastrointestinal side effects such as nausea, constipation and altered bowel habits, understanding how these effects interact with diverticular disease is essential for safe treatment. This article examines the relationship between Ozempic and diverticulitis, exploring mechanisms, risks, and practical management strategies for patients with both conditions.

What Is Ozempic and How Does It Work?

Ozempic (semaglutide) is a prescription medication licensed in the UK for the treatment of type 2 diabetes mellitus in adults. It belongs to a class of drugs known as glucagon-like peptide-1 (GLP-1) receptor agonists, which work by mimicking the action of a naturally occurring hormone that regulates blood glucose levels and appetite.

The mechanism of action of Ozempic involves several key processes. Firstly, it stimulates insulin secretion from the pancreas in a glucose-dependent manner, meaning insulin is released only when blood sugar levels are elevated. Secondly, it suppresses glucagon release, a hormone that raises blood glucose, thereby preventing excessive glucose production by the liver. Thirdly, Ozempic slows gastric emptying, which means food moves more slowly from the stomach into the small intestine. This contributes to improved post-meal blood sugar control and promotes a feeling of fullness.

Ozempic is administered as a once-weekly subcutaneous injection, typically starting at a low dose (0.25 mg for 4 weeks) and gradually increasing to therapeutic doses of 0.5 mg, 1 mg, or 2 mg, depending on individual response and tolerability. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved Ozempic specifically for glycaemic control in adults with type 2 diabetes, often in combination with other glucose-lowering medications or as monotherapy when metformin is not tolerated.

Whilst Ozempic has demonstrated significant benefits in improving HbA1c levels, with weight reduction as a secondary effect, it is important to note that it is not licensed for weight management in the UK. When used with insulin or sulfonylureas, there is an increased risk of hypoglycaemia, and doses of these medications may need adjustment. Patients should also be aware of rare but serious risks including pancreatitis, gallbladder disease, and potential worsening of diabetic retinopathy, particularly with rapid improvement in glucose control.

Understanding Diverticulitis: Causes and Symptoms

Diverticulitis is an inflammatory condition affecting the colon, characterised by infection or inflammation of small pouches called diverticula that can form in the lining of the large intestine. These pouches develop through weak spots in the bowel wall, a condition known as diverticulosis, which is extremely common in older adults and often causes no symptoms.

The exact cause of diverticulitis is not fully understood, but several factors are believed to contribute. A low-fibre diet has historically been associated with increased risk, as it may lead to harder stools and increased pressure within the colon during bowel movements. Other risk factors include obesity, lack of physical activity, smoking, and certain medications such as non-steroidal anti-inflammatory drugs (NSAIDs) and opioids. Age is also significant, with diverticular disease becoming more prevalent after 50 years.

Common symptoms of diverticulitis include:

• Persistent abdominal pain, typically in the lower left side (though it can occur on the right in some individuals)

• Fever and chills, indicating infection

• Changes in bowel habits, including constipation or diarrhoea

• Nausea and vomiting

• Bloating and abdominal tenderness

According to NICE guidance (NG147), uncomplicated diverticulitis is not routinely treated with antibiotics. Management typically involves pain relief, monitoring, and safety-netting advice. However, complicated cases involving abscess formation, perforation, peritonitis, or patients with significant comorbidities or immunosuppression require urgent hospital assessment. CT imaging may be necessary to confirm complicated disease or when diagnosis is uncertain. The severity can range from mild inflammation managed with conservative treatment to life-threatening complications requiring surgical intervention. Understanding these symptoms is crucial for patients taking medications that affect gastrointestinal function, as early recognition and appropriate management can prevent serious complications.

Gastrointestinal Side Effects of Ozempic

Gastrointestinal adverse effects are among the most commonly reported side effects of Ozempic, occurring in a significant proportion of patients, particularly during dose initiation and escalation. These effects are directly related to the drug's mechanism of action, specifically its ability to slow gastric emptying and affect gut motility.

The most frequent gastrointestinal side effects include:

• Nausea (very common: may affect more than 1 in 10 people)

• Diarrhoea (common: may affect up to 1 in 10 people)

• Constipation (common: may affect up to 1 in 10 people)

• Vomiting (common: may affect up to 1 in 10 people)

• Abdominal pain and discomfort (common)

• Dyspepsia and bloating (common)

These symptoms are typically mild to moderate in severity and often improve over time as the body adjusts to the medication. The gradual dose titration recommended by prescribers is specifically designed to minimise these effects. Most gastrointestinal symptoms are transient, resolving within the first few weeks of treatment or after dose adjustments.

It is important to note that whilst Ozempic affects bowel function and can cause abdominal discomfort, there is no established link between Ozempic and the development or worsening of diverticulitis based on current clinical evidence and product literature. However, the medication's effects on gut motility and the potential for constipation or altered bowel habits could theoretically influence symptoms in patients with pre-existing diverticular disease.

Patients should be aware of two serious conditions that can present with abdominal pain: pancreatitis and gallbladder disease. If you experience severe, persistent abdominal pain (which may radiate to your back), with or without vomiting, stop taking Ozempic and seek urgent medical attention as this could indicate pancreatitis. Similarly, right upper abdominal pain, fever or jaundice could indicate gallbladder problems, which have been reported with GLP-1 receptor agonists.

Suspected side effects should be reported via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Managing Diverticulitis While Taking Ozempic

For patients with known diverticular disease or a history of diverticulitis who are prescribed Ozempic, careful management and monitoring are essential to ensure both conditions are appropriately controlled without compromising treatment outcomes.

Dietary considerations play a crucial role. For long-term prevention of diverticulitis, patients are advised to maintain a high-fibre diet to promote regular bowel movements and reduce intracolonic pressure. However, during an acute flare of diverticulitis, dietary management differs – initially clear fluids or a low-residue diet may be recommended, with gradual reintroduction of fibre as symptoms improve. For ongoing prevention, patients should aim for gradual fibre intake (25–30g daily), adequate hydration (at least 1.5–2 litres of fluid daily, unless advised to restrict fluids due to heart or kidney conditions), and smaller, more frequent meals to manage both conditions effectively.

Monitoring bowel habits is particularly important. Patients should be alert to:

• Persistent constipation, which may increase diverticular pressure

• New or worsening abdominal pain, especially if localised to the lower abdomen

• Changes in stool consistency or frequency

• Fever or systemic symptoms suggesting infection

Communication with healthcare providers is vital. Patients should inform their GP or diabetes specialist nurse about any history of diverticular disease before starting Ozempic. If diverticulitis develops whilst taking Ozempic, treatment decisions should be made collaboratively.

During acute illness, including diverticulitis, UK 'sick day rules' should be followed. This means temporarily withholding Ozempic if you have persistent vomiting, inability to maintain fluid intake, or during significant acute illness. If you're also taking insulin or sulfonylureas, these may need adjustment to prevent hypoglycaemia when food intake is reduced. Always consult your healthcare team before making medication changes.

Medication review may be necessary if gastrointestinal side effects are problematic. Dose reduction or slower titration schedules can help manage symptoms whilst maintaining glycaemic control. Alternative GLP-1 receptor agonists or different classes of diabetes medications may be considered if Ozempic is poorly tolerated in the context of diverticular disease. Regular follow-up appointments allow for assessment of both diabetes control and gastrointestinal symptoms, ensuring optimal management of both conditions.

When to Seek Medical Advice About Ozempic and Bowel Symptoms

Knowing when to seek medical attention is crucial for patient safety, particularly when experiencing gastrointestinal symptoms whilst taking Ozempic. Whilst mild nausea and altered bowel habits are common and expected side effects, certain symptoms warrant prompt medical review.

Seek urgent medical attention (contact 999 or attend A&E) if you experience:

• Severe, persistent abdominal pain, especially if it is worsening, localised, or radiating to your back (which may indicate pancreatitis)

• High fever (above 38°C) with abdominal pain

• Heavy or ongoing rectal bleeding with dizziness, rapid heartbeat or feeling faint

• Persistent vomiting preventing fluid or medication intake

• Signs of dehydration (dizziness, reduced urination, confusion)

• Abdominal rigidity or severe tenderness on examination

These symptoms may indicate complicated diverticulitis (such as perforation, abscess, or peritonitis), pancreatitis, or other serious gastrointestinal conditions requiring immediate investigation and treatment.

Contact your GP or NHS 111 within 24–48 hours if you notice:

• New or worsening abdominal pain that differs from typical Ozempic side effects

• Persistent constipation lasting more than a few days despite dietary measures

• Minor or intermittent rectal bleeding

• Unexplained weight loss beyond expected therapeutic effects

• Gastrointestinal symptoms that do not improve after 2–3 weeks on a stable dose

• Difficulty managing blood glucose levels due to altered eating patterns

• Right upper abdominal pain, fever or yellowing of skin/eyes (possible gallbladder problems)

For routine concerns, such as mild nausea or questions about managing side effects, patients can contact their diabetes specialist nurse or practice pharmacist for advice. Many diabetes services offer telephone or email support for medication queries.

It is important to emphasise that if pancreatitis is suspected, you should stop taking Ozempic immediately and seek urgent medical attention. Do not restart if pancreatitis is confirmed. For other situations, consult your healthcare team before stopping or changing your medication, as this may affect diabetes control. Maintaining open communication with your healthcare team ensures both your diabetes and any bowel conditions are managed safely and effectively.

Report any suspected side effects to the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Frequently Asked Questions