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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Trapped Wind on Mounjaro vs Wegovy: What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) can cause trapped wind and bloating as common digestive side effects, particularly when starting or increasing doses. The main difference lies in their mechanisms: Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. This may affect how your digestive system responds. Both are prescription-only weight management injections available in the UK, and individual experiences with side effects vary considerably. Understanding these differences can help you and your prescriber decide which medication might suit your circumstances better.
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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 Work Differently
Mounjaro (tirzepatide) activates two hormone pathways simultaneously: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1. This dual mechanism slows gastric emptying more significantly, which can increase bloating and trapped wind, especially in the first four weeks. The SURMOUNT clinical trial showed average weight loss of 15–21% body weight depending on dose.
Wegovy (semaglutide) activates only the GLP-1 pathway. It still slows gastric emptying but through a single mechanism, which some users report causes less intense digestive disruption. The STEP trial data showed average weight loss of approximately 15% body weight at the maximum 2.4 mg dose.
Neither medication contains ingredients that directly cause gas production — trapped wind results from slower food movement through your stomach and intestines, combined with reduced appetite and smaller portion sizes. Both are available on NHS specialist weight management services or through private prescription after clinical assessment.
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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 Trapped Wind: Individual Suitability
Trapped wind severity varies dramatically between individuals on both medications. Some people experience only mild bloating during the first two weeks; others report more persistent symptoms lasting several weeks. Your prescriber will assess which medication suits you based on your medical history, current conditions, and any previous digestive issues.
If trapped wind becomes problematic on one medication, switching to the other is possible — though this requires a new clinical assessment and typically a washout period. Strategies like eating slowly, staying hydrated, gentle movement, and eating smaller portions help regardless of which medication you take. Use our free GLP-1 weight loss calculator to explore projected outcomes with either medication, then discuss your concerns about digestive side effects with your prescriber before starting.
- 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.
Which causes more trapped wind — Mounjaro or Wegovy?
Mounjaro's dual GIP+GLP-1 mechanism may cause more pronounced gastric slowing initially, potentially leading to greater trapped wind in the first 4 weeks. Wegovy's single GLP-1 pathway may be gentler for some people. However, individual responses vary significantly — some users tolerate Mounjaro well whilst others report more bloating on Wegovy. Your prescriber will consider your medical history when deciding.
How long does trapped wind last on these injections?
Trapped wind is typically most noticeable in the first two to four weeks after starting or increasing doses. For many people, symptoms improve as your body adjusts and you find sustainable portion sizes. If trapped wind persists beyond six weeks, discuss this with your prescriber — dose adjustment or medication switch may help.
Can I reduce trapped wind symptoms without stopping the injection?
Yes. Eat slowly in small portions, stay well hydrated, avoid carbonated drinks, take gentle walks after meals, and ensure you're eating enough fibre. Some people find ginger tea or peppermint helpful. If symptoms remain severe, contact your prescriber — they can adjust your dose or explore alternatives like Wegovy if you started on Mounjaro.
Do I need a different prescription if I switch from Mounjaro to Wegovy?
Yes. Switching between medications requires a new clinical assessment by your prescriber. They will review whether the alternative is suitable for your health circumstances, discuss any washout period needed, and issue a new prescription. You cannot simply switch without professional guidance.
Is trapped wind a serious side effect I should worry about?
Trapped wind is very common but not dangerous. However, if you experience severe persistent stomach pain, vomiting, or pain radiating to your back, contact your GP immediately — these could indicate pancreatitis, which is rare but requires urgent assessment. Mild bloating and trapped wind typically resolve within weeks.
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