Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. Whilst Mounjaro does not directly cause haemorrhoids, its gastrointestinal effects—particularly constipation and altered bowel habits—may indirectly contribute to their development or worsening. Understanding this connection helps patients and healthcare professionals manage digestive symptoms effectively. This article examines the relationship between Mounjaro and haemorrhoids, explores the medication's gastrointestinal side effects, and provides practical guidance on symptom management and when to seek medical advice.

What Is Mounjaro and How Does It Work?

Mounjaro (tirzepatide) is a prescription medication licensed in the UK for the treatment of type 2 diabetes mellitus. In the UK, tirzepatide is also available under the brand name Zepbound for weight management in adults with obesity or overweight with weight-related comorbidities. Mounjaro belongs to a novel class of medicines known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. This dual mechanism distinguishes Mounjaro from other GLP-1 receptor agonists currently available.

The medication works by mimicking the action of two naturally occurring incretin hormones that are released after eating. GLP-1 stimulates insulin secretion when blood glucose levels are elevated, suppresses glucagon release (which reduces glucose production by the liver), slows gastric emptying, and promotes satiety through effects on appetite centres in the brain. GIP also enhances insulin secretion and may have effects on fat metabolism. Together, these actions help improve glycaemic control in people with type 2 diabetes and facilitate weight loss primarily through reduced appetite and decreased food intake.

Mounjaro is administered as a once-weekly subcutaneous injection, typically starting at a non-therapeutic dose of 2.5 mg for 4 weeks to improve tolerability. The dose is then gradually increased in 2.5 mg increments based on clinical response and side effects. The therapeutic maintenance dose ranges from 5 mg to 15 mg weekly. By slowing the movement of food through the digestive system and reducing appetite, Mounjaro can lead to significant improvements in HbA1c levels and body weight. However, these gastrointestinal effects also contribute to the medication's side effect profile, which patients and healthcare professionals must carefully consider and manage.

Gastrointestinal Side Effects of Mounjaro

Gastrointestinal adverse effects are the most commonly reported side effects associated with Mounjaro, occurring in a substantial proportion of patients, particularly during dose initiation and escalation. The most frequent symptoms include nausea (affecting approximately 18-24% of patients), diarrhoea (15-17%), vomiting (6-10%), constipation (6-13%), abdominal pain (6-10%), and dyspepsia (5-9%). According to clinical trials and the MHRA-approved product information, these effects are generally mild to moderate in severity and tend to diminish over time as the body adapts to the medication.

Constipation deserves particular attention when considering the potential link between Mounjaro and haemorrhoids. The slowing of gastric emptying and intestinal transit—whilst beneficial for glycaemic control and satiety—can lead to harder stools and straining during bowel movements. Chronic constipation and straining are well-established risk factors for the development or exacerbation of haemorrhoids. When increased intra-abdominal pressure is repeatedly applied during defecation, it can cause swelling and inflammation of the vascular cushions in the anal canal, leading to symptomatic haemorrhoids.

Conversely, some patients experience diarrhoea with Mounjaro, which can also contribute to anal irritation and discomfort. Frequent loose stools may cause local inflammation and worsen pre-existing haemorrhoidal symptoms. It is important to note that there is no official direct pharmacological link between tirzepatide and haemorrhoid formation—the medication does not specifically target anal vascular tissue. Rather, any association appears to be indirect, mediated through alterations in bowel habits.

Patients with severe gastrointestinal disease, including severe gastroparesis, may experience more problematic digestive symptoms whilst taking Mounjaro. Healthcare professionals should take a thorough gastrointestinal history before initiating treatment and counsel patients accordingly about potential bowel habit changes. Patients should also be informed about serious gastrointestinal adverse events that require urgent medical attention, including severe persistent abdominal pain (with or without vomiting) which may indicate pancreatitis, symptoms of gallbladder disease, or signs of dehydration.

Managing Digestive Symptoms While Taking Mounjaro

Effective management of gastrointestinal side effects is crucial for maintaining treatment adherence and preventing complications such as haemorrhoids. Dietary modifications form the cornerstone of symptom management. Patients should be advised to increase their fibre intake gradually through consumption of fruits, vegetables, whole grains, and legumes, aiming for 25–30 grams daily. Adequate hydration is equally important—drinking 6-8 glasses (1.2–1.5 litres) of water daily helps soften stools and facilitates regular bowel movements. This intake should be increased during hot weather or if experiencing diarrhoea or vomiting to prevent dehydration.

Eating smaller, more frequent meals rather than large portions can help minimise nausea and abdominal discomfort. Patients should avoid foods that are high in fat, overly spicy, or known to cause personal digestive upset. Eating slowly and chewing thoroughly allows the digestive system to process food more effectively, which is particularly important given Mounjaro's effect on gastric emptying.

For those experiencing constipation, bulk-forming laxatives such as ispaghula husk (psyllium) or methylcellulose may be recommended as first-line options after consulting a pharmacist or GP. These should be taken with plenty of water. If constipation persists, osmotic laxatives like macrogol (polyethylene glycol) may be considered. Stimulant laxatives should generally be reserved for short-term use under medical guidance. Regular physical activity—even moderate walking—can stimulate intestinal motility and help prevent constipation.

Proper toilet habits are essential for preventing haemorrhoids. Patients should be counselled to respond promptly to the urge to defecate rather than delaying, avoid straining or spending excessive time on the toilet, and consider using a footstool to elevate the knees above hip level, which facilitates easier bowel movements. If diarrhoea is problematic, maintaining hydration and electrolyte balance is paramount, and temporary simple dietary adjustments may provide relief. For patients with diagnosed irritable bowel syndrome, a low-FODMAP diet might be considered, but only under the guidance of a dietitian.

Healthcare professionals should review the dose escalation schedule if gastrointestinal symptoms are particularly troublesome. Slowing the rate of dose titration or temporarily maintaining a lower dose may allow better tolerance whilst still achieving therapeutic benefits. The MHRA-approved prescribing information provides specific guidance on dose adjustment strategies for managing adverse effects.

When to Seek Medical Advice About Haemorrhoids

Whilst mild haemorrhoidal symptoms may be managed with conservative measures, certain presentations warrant prompt medical evaluation. Patients should contact their GP if they experience rectal bleeding, even if they suspect it is due to haemorrhoids. Although bright red blood on toilet paper or in the toilet bowl is characteristic of haemorrhoids, it is essential to exclude other causes, including colorectal polyps, inflammatory bowel disease, or malignancy. According to NICE guidance (NG12), unexplained rectal bleeding in adults aged 50 or over may require an urgent two-week referral to exclude colorectal cancer. GPs may use faecal immunochemical testing (FIT) to help guide referral decisions for lower-risk symptoms.

Severe or persistent pain in the anal region requires medical assessment, as it may indicate thrombosed external haemorrhoids or an anal fissure, both of which may require specific treatment. Prolapsing haemorrhoids that cannot be manually reduced, or those associated with significant discomfort, should also be evaluated by a healthcare professional. NICE Clinical Knowledge Summary (CKS) on haemorrhoids recommends that patients with persistent or troublesome symptoms should be examined and may require referral to a colorectal specialist.

Signs of complications that necessitate urgent medical attention include severe bleeding leading to anaemia (symptoms: fatigue, pallor, breathlessness), fever or signs of infection, or inability to control bowel movements. Patients should call 999 or go to A&E immediately for heavy rectal bleeding, especially if accompanied by dizziness, fainting, or signs of shock. Black or tarry stools require urgent medical assessment as they may indicate bleeding higher in the digestive tract.

Patients taking Mounjaro should also seek urgent medical advice if they develop sudden severe, persistent abdominal pain (which may radiate to the back and be accompanied by vomiting), as this could indicate acute pancreatitis—a rare but serious adverse effect of GLP-1 receptor agonists including tirzepatide.

It is important for patients to maintain open communication with their diabetes care team or prescribing clinician about any gastrointestinal symptoms experienced whilst taking Mounjaro. The benefits of continuing treatment must be weighed against the impact of side effects on quality of life. In some cases, alternative medications or adjusted treatment regimens may be more appropriate. Patients should be encouraged to report any suspected side effects to the MHRA Yellow Card Scheme, which helps monitor the safety of medicines after they have been licensed. Healthcare professionals can provide individualised advice on symptom management, prescribe appropriate treatments for haemorrhoids, and determine whether specialist referral is indicated.

Frequently Asked Questions