Experiencing diarrhoea on Mounjaro? Here’s how to ease symptoms

For many women, starting a new weight loss medication like Mounjaro can be exciting, especially when you're focused on achieving real, sustainable results. But it's not always smooth sailing.

One of the most common hurdles in the early weeks is gastrointestinal upset, with diarrhoea being a particularly uncomfortable side effect for many.

The good news? There are practical, evidence-backed ways to manage diarrhoea, ease discomfort, and keep progressing on your weight loss journey.

In this article, we'll walk you through what causes diarrhoea on Mounjaro, how long it tends to last, and what you can do to feel better, without derailing your efforts.

Is diarrhoea a common side effect of Mounjaro?

Yes. In fact, it's one of the most common side effects of Mounjaro, particularly in the early stages of treatment.

Mounjaro (tirzepatide) is a once-weekly weight loss injection that works by mimicking the effects of two natural gut hormones: GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) [1]. Together, these receptor agonists help regulate appetite, slow digestion, and support blood sugar control [2].

While this is part of what makes Mounjaro so effective for weight management, these changes to gut motility and digestive processes can also cause temporary gastrointestinal adverse events, including nausea, decreased appetite, abdominal discomfort, and diarrhoea.

In clinical trials, patients treated with Mounjaro reported diarrhoea more frequently than those on placebo [3]. However, most cases were mild to moderate and resolved within a few days or weeks, and became less common as the body adjusted.

How long does diarrhoea from Mounjaro last?

For most people, diarrhoea on Mounjaro is temporary. It typically starts shortly after beginning treatment or increasing your Mounjaro dosage and subsides within the first few weeks as your body adjusts.

That said, how long it lasts can vary. Some patients experience only a few days of loose stools, while others may notice intermittent diarrhoea for several weeks. The good news is that in the majority of cases, this side effect gradually lessens without needing to stop treatment.

If diarrhoea persists, or worsens beyond a few weeks, especially if it leads to dehydration, severe abdominal pain, or impacts your daily life, it's important to speak to your healthcare provider.

How to stop or manage diarrhoea on Mounjaro

While it can be uncomfortable, there are several simple ways to manage diarrhoea on Mounjaro:

1. Stay hydrated

Losing fluids through diarrhoea can quickly lead to dehydration, especially if it's persistent [4]. Make sure you're drinking plenty of fluids throughout the day. Oral rehydration salts, bone broth, and electrolyte drinks can help replace lost nutrients and support your digestive system [4].

2. Eat small, gentle meals

Opt for small portions or bland, easy-to-digest foods, such as bananas, plain rice, toast, apples, and boiled potatoes. Avoid greasy, spicy, and high-fat foods, as they can irritate the gut.

3. Keep a food diary

Tracking what you eat can help you identify whether certain foods are triggering or worsening diarrhoea. Common culprits include dairy, artificial sweeteners, caffeine, and fried food.

4. Use over-the-counter medicine (if approved)

In some cases, medications like loperamide (Imodium) may help manage symptoms [5]. However, always check with your doctor or pharmacist before taking anything new, especially while on prescription weight loss medications.

5. Avoid alcohol and excessive caffeine

Both alcohol and caffeine can irritate your digestive tract and worsen diarrhoea [4][6]. Limit your intake while your body adjusts.

6. Support your gut with fibre (when ready)

Once diarrhoea starts to settle, gradually reintroduce high-fibre foods like oats, lentils, and cooked vegetables to support your gut health and regularity.

What to do if diarrhoea becomes severe

While mild diarrhea is a common side effect of Mounjaro, severe diarrhoea, especially when accompanied by other serious symptoms, should not be ignored.

Contact your health provider immediately if you experience [4]:

• Severe diarrhoea lasting more than a few days
• Signs of dehydration (dry mouth, dizziness, dark urine)
• Severe stomach or belly pain
• High fever or chills
• Severe vomiting or difficulty breathing
• Blood in your stools
• Sudden weight loss unrelated to your treatment goals

These could be a sign of a more serious gastrointestinal adverse event or an underlying condition. In rare cases, Mounjaro may cause a serious allergic reaction or require medical intervention.

Can Mounjaro cause sickness and diarrhoea together?

It is possible. Some patients report nausea, vomiting, and diarrhoea when starting Mounjaro, especially in the early adjustment phases or following a dose increase [7].

This is due to how Mounjaro affects the digestive system. By slowing down gut motility and delaying stomach emptying, the medication can disrupt normal digestive rhythms, particularly before your body adapts.

If you're experiencing both nausea and diarrhoea, eating small meals, drinking fluids steadily, and avoiding high-fat or acidic foods can help reduce symptoms. Anti-sickness tablets may be recommended in some cases, but always consult your healthcare provider before starting new treatment.

Tips to prevent diarrhoea when starting Mounjaro

Prevention is often easier than treatment. If you're preparing to start or increase your Mounjaro dosage, these strategies may help minimise the risk of diarrhoea:

• Ease into fibre: High-fibre foods are great for weight loss, but a sudden increase can cause digestive upset. Introduce them gradually.
• Avoid greasy foods: These can overwhelm your digestive system while it's adjusting to the medication.
• Eat small portions: Large meals can trigger or worsen gastrointestinal symptoms. Instead, eat smaller meals more frequently.
• Keep a food diary: Track what you eat and how you feel after to spot any patterns.
• Limit acidic or spicy foods: These can trigger acid reflux, stomach pain, or worsen diarrhoea.
• Don't skip meals: Going too long without eating can trigger nausea, low blood sugar, or digestive upset, all of which can exacerbate gastrointestinal side effects of Mounjaro.

When to speak to your healthcare provider?

If diarrhoea or other side effects of Mounjaro are affecting you persistently, don't hesitate to reach out for support. You should contact your healthcare provider if:

• Diarrhoea persists beyond a few weeks or worsens
• You develop severe cases of gastrointestinal upset or dehydration
• You have a personal or family history of kidney disease, digestive issues, or food intolerances
• You experience symptoms like severe abdominal pain, acid reflux, or vomiting
• You're unsure whether the medication is working or if your body is adjusting properly

In rare cases, Mounjaro may increase the risk of serious side effects, including pancreatitis, thyroid cancer (especially in patients with a personal or family history), or serious allergic reactions. If you notice symptoms like a lump in the neck, difficulty breathing, hoarseness, or swelling of the face or throat, seek medical attention immediately — this could be a medical emergency [8].

Support your weight loss journey with Juniper

Experiencing side effects like diarrhoea can be discouraging, but it doesn't mean Mounjaro isn't right for you. Often, these are signs that your body is adjusting to the new medication.

At Juniper, we understand that successful weight loss isn't just about the number on the scale; it's about feeling supported, confident, and in control.

Juniper's Weight Loss Reset Programme combines weight loss medication with dietitian-led health coaching and tracking, so you can lose weight and reach your goals for good.

Kickstart your weight loss journey with Wegovy or Mounjaro, two groundbreaking weight loss medications that mimic the GLP-1 and GIP hormones, respectively, to help control cravings, delay stomach emptying, and keep you feeling fuller for longer. These clinically backed treatments help members experience up to 20% body weight loss.

Plus, we have a team of expert dietitians and health coaches you can consult with to help you work through any challenges you're experiencing during your weight management journey. This approach sets you up for sustained weight loss, rather than a quick-fix solution.

This means you can continue to enjoy the things you love in moderation without ever feeling deprived.

Ready to see if Juniper is right for you? You can check your eligibility here.

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