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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Does Mounjaro Cause More Bloating Than Wegovy?
Bloating is a common concern for people considering Mounjaro or Wegovy. Both medications can cause abdominal discomfort, though individual experiences vary significantly. The underlying reason is different: Mounjaro (tirzepatide) uses a dual GIP and GLP-1 mechanism, while Wegovy (semaglutide) is a GLP-1-only medication. Understanding how each works, what clinical trials showed, and how your prescriber might support you can help you make an informed decision about which prescription medication suits your circumstances.
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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.
How Mounjaro and Wegovy Cause Bloating — Mechanism Differences
Mounjaro (tirzepatide) activates two hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1. This dual action slows gastric emptying (how quickly food leaves your stomach) more significantly than GLP-1 alone, which is why some people experience more pronounced bloating or abdominal distension early on.
Wegovy (semaglutide) activates only the GLP-1 pathway, which also slows gastric emptying but through a single mechanism. Clinical trials (STEP for Wegovy, SURMOUNT for Mounjaro) both reported bloating and stomach discomfort as very common side effects—affecting more than 1 in 10 people—but the SURMOUNT data suggested slightly higher rates of gastrointestinal distress with Mounjaro at higher doses.
- Both medications slow how your stomach empties
- Both are prescription-only and require UK clinical assessment
- Bloating typically improves over weeks as your body adjusts
- Dose titration (gradual increases) may reduce early bloating severity
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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.
Free Weight Loss Tools & Guides
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Individual Suitability — Why Your Prescriber's Assessment Matters
Neither Mounjaro nor Wegovy is "better" for bloating—individual response is highly variable. Some people tolerate one medication better than the other; others experience minimal symptoms with either. Your prescriber will assess your medical history, any existing stomach conditions (like gastroparesis), and your personal tolerance when deciding which is appropriate for you.
If bloating becomes bothersome, your prescriber may recommend staying at a lower dose longer, adjusting meal sizes, or switching medications. This is why both require prescription through a UK-licensed prescriber following a clinical assessment, not just self-selection. Using our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses, but your prescriber makes the final medication choice based on your individual profile.
- 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.
Is Mounjaro bloating worse than Wegovy bloating?
Clinical trial data (SURMOUNT for Mounjaro, STEP for Wegovy) shows both cause bloating in more than 1 in 10 people. Mounjaro's dual mechanism may cause slightly more pronounced early symptoms, but individual response varies greatly. Some people tolerate Mounjaro better and others prefer Wegovy. Your prescriber will assess which suits your circumstances.
How long does bloating last on Mounjaro or Wegovy?
Bloating typically improves within 2–4 weeks as your body adjusts to the medication. Dose titration (starting low and gradually increasing every 4 weeks) can help reduce severity. If bloating persists beyond 6–8 weeks, inform your prescriber—they may adjust your dose or consider switching medications.
Can I take anything to reduce bloating on these injections?
Your GP or prescriber may suggest smaller, more frequent meals; increasing water intake; reducing high-fibre foods initially; or gentle movement. Over-the-counter remedies like simethicone may help. Always check with your prescriber before adding any medication or supplement, as these injections can affect how your stomach empties.
Which medication is prescribed more on the NHS in the UK?
Both Mounjaro and Wegovy are now licensed in the UK and available through NHS specialist tier 3 weight management services, though access varies significantly by region and waiting lists can be lengthy. Private online prescribing is also available for both. Your GP referral pathway and local ICB (Integrated Care Board) availability determine which is offered to you.
Why does tirzepatide cause more gastrointestinal issues than semaglutide?
Tirzepatide (Mounjaro) activates two hormone pathways (GIP + GLP-1), whereas semaglutide (Wegovy) activates GLP-1 only. The dual mechanism slows gastric emptying more significantly, which can intensify bloating and nausea early on. However, this same dual action may also contribute to slightly greater average weight loss—results vary between individuals.
Ready to take control of your weight loss journey?
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