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
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Bloating on Mounjaro: How It Compares to Wegovy
Feeling bloated on Mounjaro is one of the most commonly reported side effects of tirzepatide treatment. Many people wonder whether Wegovy (semaglutide) causes fewer digestive issues, or if bloating is simply part of GLP-1 and GIP receptor agonist therapy. The truth is more nuanced: both medications can cause bloating, but the underlying mechanisms and individual experiences differ. This guide compares the two based on clinical trial data and UK prescriber experience to help you understand what to expect and when to discuss concerns with your GP.
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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.
Why Bloating Happens: Mounjaro vs Wegovy Mechanisms
Mounjaro (tirzepatide) works as a dual GIP and GLP-1 receptor agonist, meaning it activates two separate hormone pathways. This dual mechanism may be why some users report more pronounced digestive side effects, including bloating. The medication slows gastric emptying—how quickly food leaves your stomach—which can create a sensation of fullness and abdominal distension, particularly in the first 4–8 weeks of treatment.
Wegovy (semaglutide) is a GLP-1-only receptor agonist with a single mechanism of action. Clinical trials (STEP-1) reported nausea, diarrhoea, and constipation as the most common gastrointestinal effects, with bloating mentioned less frequently than with Mounjaro. However, bloating still occurs in some Wegovy users, especially during the dose titration phase.
- Mounjaro: gastrointestinal side effects reported by approximately 40–50% of users in SURMOUNT trials
- Wegovy: gastrointestinal side effects reported by approximately 30–40% in STEP trials
- Both medications slow stomach emptying, but Mounjaro's dual mechanism may intensify this effect
- Individual responses vary significantly—some users report minimal bloating, others experience more pronounced symptoms
The difference is not that one is universally "better"—it's that the dual mechanism of Mounjaro may create a different side effect profile for some individuals, and only a prescriber can assess which is more suitable for you.
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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.
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Managing Bloating and When to Seek Prescriber Advice
If you're feeling bloated on Mounjaro, several practical steps may help: stay hydrated, eat slowly and in smaller portions, avoid carbonated drinks and high-fat foods, and increase gentle physical activity like walking. Most bloating improves after the first 4–8 weeks as your body adjusts to the medication. Your prescriber may also adjust your dose titration schedule—staying on a lower dose for longer before escalating can reduce digestive symptoms.
Contact your GP or prescriber if bloating is severe, persistent beyond 12 weeks, accompanied by severe stomach pain, or affecting your ability to eat. In rare cases, bloating can signal a more serious digestive issue that requires medical assessment. Use our free GLP-1 weight loss calculator to track how your symptoms correlate with dose changes, and our progress tracker to monitor both weight and how you're tolerating the medication week by week.
- 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.
Does Mounjaro cause more bloating than Wegovy?
Clinical trial data suggests Mounjaro users report gastrointestinal side effects (including bloating) slightly more frequently than Wegovy users, likely due to tirzepatide's dual GIP+GLP-1 mechanism. However, individual experiences vary significantly—some Mounjaro users experience minimal bloating, whilst some Wegovy users report more pronounced symptoms. Only a prescriber can determine which is more suitable for your individual health profile.
How long does bloating last on Mounjaro?
Most bloating improves after 4–8 weeks as your body adjusts to the medication. If you're still experiencing significant bloating after 12 weeks, discuss this with your prescriber—they may recommend staying on your current dose longer before escalating, or they may suggest an alternative medication.
Can I switch from Mounjaro to Wegovy to reduce bloating?
Possibly, but only your prescriber can determine whether a switch is appropriate. If bloating is severely affecting your quality of life, discuss this concern with your GP or the clinic prescribing your medication. A switch typically involves a washout period and careful dose titration on the new medication.
What should I eat to reduce bloating on Mounjaro?
Eat slowly in smaller portions, avoid carbonated drinks, fried foods, and high-fat meals which slow digestion further. Focus on lean proteins, vegetables, wholegrains, and hydration. Many users find that softer, easier-to-digest foods reduce bloating during the first weeks of treatment.
Is bloating on Mounjaro a sign the medication isn't working?
No. Gastrointestinal side effects like bloating are unrelated to weight loss efficacy. The medication can still be helping you lose weight whilst causing temporary digestive discomfort. If concerned, your prescriber can review your progress using our free BMI calculator and weight converter to confirm the medication is effective for you.
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.