Dealing with Mounjaro diarrhoea

Diarrhoea is one of the most common side effects people experience when taking Mounjaro. In clinical trials, around 16% of patients said they experienced it, making it more common than constipation.

While you might know that some digestive changes can happen when starting treatment, dealing with frequent or urgent trips to the toilet can still be uncomfortable, disruptive and understandably frustrating.

For most people, this symptom improves with a few lifestyle and diet changes or as your body naturally adjusts to the medication. Still, understanding why Mounjaro causes diarrhoea is a useful first step towards managing it.

In this guide, we’ll explain it, alongside covering practical ways to help settle your symptoms, and when diarrhoea means it’s time to speak to a healthcare professional.

Why does Mounjaro cause diarrhoea?

Part of how Mounjaro works involves changing the way your digestive system processes food. These changes can affect gut function, which is why some people experience side effects like diarrhoea.

Here are the main reasons why this can happen:

• Slowed gastric emptying: The medication slows down how quickly food leaves your stomach, signalling a change to your gut motility (basically, how fast food passes through your digestive system). While this helps you feel fuller for longer, it can also trigger diarrhoea.
• Shifts in the gut microbiome: Early research is exploring whether tirzepatide affects the community of microorganisms living in the gut. However, it is not yet clear whether these changes contribute to diarrhoea in people taking Mounjaro.

While side effects usually settle as the body adapts, understanding these processes helps explain why some people may experience diarrhoea while taking Mounjaro, especially when first starting treatment.

How to stop diarrhoea on Mounjaro

If you’re dealing with diarrhoea on Mounjaro right now, the priority is to replace the fluids you’re losing, be gentle on your digestive system and give yourself time to recover. Most cases of diarrhoea settle within a few days, but there are things you can do to make yourself more comfortable in the meantime.

• Keep sipping fluids: Diarrhoea can quickly leave you dehydrated. Drink water little and often, especially if you’re also feeling nauseous. An electrolyte drink can also help replace the fluids and salts you’ve lost.
• Eat when you feel able: You shouldn't force yourself to eat, but you don’t need to avoid food either. When you’re ready, choose simple, easy-to-digest foods such as white rice, white pasta, white bread or mashed potato, and give fatty or spicy foods a miss while your stomach settles.
• Give your body a break: Diarrhoea can leave you feeling tired and drained, particularly when you’re losing fluids. If you can, slow things down and rest while your symptoms settle.
• Consider loperamide if it’s suitable for you: Loperamide, also known by the brand name Imodium, can help adults manage short-term diarrhoea. Follow the packet instructions and do not take it for more than 48 hours without speaking to a doctor. Ask a pharmacist or doctor before using it if you have other symptoms or health conditions.

If your diarrhoea is particularly difficult to manage, you can’t keep fluids down or you’re showing signs of dehydration, speak to your myBMI clinician or seek medical advice so you can get the right support.

How to prevent diarrhoea on Mounjaro

If you’ve experienced diarrhoea on Mounjaro before, getting to know what your digestive system tolerates can help you feel more prepared. You may not be able to prevent every episode, but a few simple habits can help you look after your gut and reduce things that could make symptoms worse.

• Get to know your trigger foods: Pay attention to whether certain foods or meals seem to be followed by diarrhoea. Keeping a simple food and symptom diary can make patterns easier to spot, so you can temporarily limit foods that repeatedly cause problems.
• Keep meals smaller and simpler: Mounjaro reduces your appetite, so there’s no need to push yourself to finish a large portion when you already feel full. Try smaller meals and take your time, stopping when you feel comfortably satisfied.
• Go easy on rich, fatty or spicy foods: If you know your digestive system is feeling sensitive, choosing simpler meals may be more comfortable.
• Stay well hydrated: Make drinking regularly part of your everyday routine, particularly if you’ve already experienced diarrhoea. The official Mounjaro patient information leaflet warns that diarrhoea, vomiting and nausea can cause fluid loss and dehydration, so keeping your fluids topped up is important.
• Stick to your prescribed Mounjaro dose: Don’t reduce, increase or otherwise change your dose yourself because of diarrhoea. The official patient information advises following your prescribed dosing schedule and speaking to your clinician about side effects.

If your diarrhoea keeps coming back, speak up! You don’t have to simply put up with repeated symptoms. If diarrhoea is becoming a regular part of your experience with Mounjaro or is difficult to manage, talk to your clinician so they can advise you on the safest next step.

Dietary adjustments for diarrhoea

Foods to eat when dealing with Mounjaro diarrhoea

When your gut is unsettled, eating the right foods can help calm things down and give your body a chance to recover. Examples include:

• Bananas, rice, applesauce, and toast (also known as the BRAT diet): These foods are easy to digest, which makes them gentle on an irritated stomach. They can also help firm up stools and replace some of the nutrients lost during diarrhoea.
• Lean proteins: Foods like chicken, turkey or white fish are good protein sources without added fat. Lean protein supports recovery after exercise and helps keep your energy up while still being easier on the digestive system than fatty or fried meats.
• Probiotics: These help support a healthy gut balance. You can find them in yoghurt with live cultures, kefir or probiotic supplements. Adding probiotics may help restore balance in your gut microbiome after a spell of diarrhoea.
• Soups: Warm, clear soups and broths are easy to digest and can help you stay hydrated while providing some nutrients. Soups with soft vegetables or a little lean protein are ideal, while creamy or spicy soups should be avoided until symptoms ease.

Foods to avoid while suffering from Mounjaro diarrhoea

Just as some foods can help, others can make diarrhoea worse. Avoiding these while your stomach settles can make a big difference. You should try to avoid eating the following foods:

• High fibre foods: Normally, fibre is great for digestion. But when you have diarrhoea, too much fibre can speed up gut movement and make stools looser.
• Spicy foods: Spices and chilli can irritate the stomach and intestines. If you’re already dealing with diarrhoea, spicy foods could worsen the problem and should be avoided until things settle down.
• Caffeine and alcohol: Both caffeine and alcohol can upset your stomach and make diarrhoea worse. They also make it harder for your body to stay hydrated, which is especially important when you’re losing fluids. Try avoiding coffee, fizzy energy drinks and alcohol until your stomach has settled.
• High-gas vegetables: Vegetables like broccoli, cabbage, beans and onions are harder to digest and can cause gas and bloating. These effects may worsen diarrhoea, so it’s best to avoid them until your stomach has calmed down.

When should you be see a doctor?

Most of the time diarrhoea caused by Mounjaro is mild and settles down as your body adjusts. But sometimes, it can be a sign that you need medical advice. It’s a good idea to contact your doctor if you notice:

• diarrhoea lasting more than a few days without improvement
• severe or worsening diarrhoea
• signs of dehydration such as dizziness, dark urine or often feeling very thirsty
• unexplained fatigue
• a persistent feeling of needing to have a bowel movement even after defecation.

You should seek urgent in-person medical care if

• diarrhoea persists
• you are unable to keep fluids down
• have reduced urination
• are dizzy / have collapsed
• have severe abdominal pain
• notice blood in your stool
• your symptoms are lasting longer than 48-72 hours

“Diarrhoea can be uncomfortable and disruptive to your day, but you don’t have to just put up with it. Keep your fluids topped up, be gentle with yourself and reach out to your clinical team if you’re struggling. We’re here to help you feel supported throughout your treatment.”

Niya MansuriPrescribing Pharmacist

What are other side effects of Mounjaro?

Diarrhoea isn’t the only side effect you might experience while taking Mounjaro. Other common side effects include nausea, dizziness, constipation, and vomiting, although everybody’s experience of treatment is different.

For a fuller picture of what you might experience and how to manage it, read our guide to Mounjaro side effects.

Getting support throughout your treatment

Your weight loss journey shouldn’t be something you have to navigate alone. If diarrhoea or other side effects are making treatment more difficult, reaching out for support can help you understand what you’re experiencing and what to do next.

At myBMI, our clinicians are with you throughout your treatment, so you can get advice when you need it and feel supported at every step of the way.

Already a myBMI patient?

Speak to your clinician if you’re experiencing diarrhoea or any other side effects. They’re there to listen, offer guidance and help you manage your treatment safely.

Thinking about starting Mounjaro?

Learn more about our Mounjaro treatment plan and the support available throughout your journey.

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