The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
How to Manage Constipation While Taking Mounjaro
Constipation is one of the most common side effects of Mounjaro (tirzepatide), affecting more than 1 in 10 people taking the medication. If you're experiencing constipation while on this prescription weight management injection, there are practical steps you can take to manage it alongside your treatment. This guide explains what causes constipation with Mounjaro, simple management strategies, and when to speak with your GP about your symptoms.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Understanding Constipation With Mounjaro
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by slowing how quickly food moves through your stomach—a process called gastric emptying. While this effect helps reduce appetite, it can also slow overall digestive movement, leading to constipation. This side effect typically occurs during the dose titration phase and may improve as your body adjusts.
The constipation associated with Mounjaro is usually mild to moderate and manages well with lifestyle changes. However, it's important to distinguish between typical constipation and serious symptoms—severe abdominal pain spreading to the back can indicate pancreatitis, which requires immediate medical attention.
- Constipation commonly occurs in the first 4–8 weeks of treatment
- Risk may increase at higher doses (10 mg, 15 mg)
- Most people find symptoms improve with simple management strategies
- Always inform your GP if constipation persists or worsens
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Practical Constipation Management Strategies
Increase water intake: Drink at least 2–3 litres of water daily. Dehydration worsens constipation significantly, especially when taking Mounjaro.
Add dietary fibre gradually: Include more soluble fibre (oats, apples, beans) rather than insoluble fibre initially, which can cause bloating. Increase slowly to avoid gas.
Physical activity: Regular movement—even 20–30 minutes of walking daily—stimulates bowel motility naturally. Exercise is also part of successful weight management alongside your Mounjaro KwikPen injections.
Over-the-counter remedies: Osmotic laxatives like lactulose or polyethylene glycol (PEG) are generally safe with Mounjaro. Ask your pharmacist for recommendations. Avoid stimulant laxatives initially.
Meal timing: Eat smaller, more frequent meals rather than large meals, which aligns with how Mounjaro affects appetite anyway.
If constipation persists after 2–3 weeks of these strategies, contact your GP. They may adjust your Mounjaro dose schedule or recommend prescription stool softeners if needed. Never stop taking your medication without medical guidance.
Track any changes alongside your weight progress using our free progress tracker to spot patterns between dose changes and symptom intensity. Your prescriber may also suggest temporarily staying at your current dose longer during titration rather than escalating to allow your digestive system to adjust.
Remember that while managing side effects is important, Mounjaro has helped many people achieve significant weight loss—evidence suggests an average of 15–clinically studied weight loss in clinical trials—and constipation is typically temporary and manageable.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long does constipation last when taking Mounjaro?
Most people experience constipation during the first 4–8 weeks, particularly during dose titration. As your body adjusts and you implement management strategies, symptoms often improve. Some people find it continues at higher doses. Always inform your GP if it persists beyond 2–3 weeks of lifestyle management.
Is constipation a serious side effect of Mounjaro?
Typical constipation with Mounjaro is common but usually not serious and responds well to hydration, fibre, and movement. However, severe abdominal pain spreading to the back could indicate pancreatitis—a rare but serious complication requiring immediate medical attention. Contact NHS 111 or A&E if you experience severe pain.
Can I take laxatives while using Mounjaro?
Yes, osmotic laxatives like lactulose and polyethylene glycol are generally safe with Mounjaro. Avoid stimulant laxatives initially as they may interact unpredictably. Ask your pharmacist for specific recommendations, and always inform your GP about any laxatives you're taking regularly.
Should I stop taking Mounjaro if constipation is severe?
No—never stop taking Mounjaro without medical guidance, even if constipation is troublesome. Speak with your GP or the prescriber who issued your prescription. They can adjust your dose schedule, recommend medication, or explore other solutions. Stopping suddenly is not appropriate.
Does constipation affect weight loss on Mounjaro?
Temporary constipation doesn't typically prevent weight loss on Mounjaro. Clinical trials showed consistent weight loss across doses regardless of digestive side effects. Weight loss depends on the medication's appetite-regulating effects combined with a reduced-calorie diet and increased physical activity—not on bowel regularity.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.