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
Mounjaro Bloated Stomach vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription weight loss injections licensed in the UK, and bloating can occur with either. The key difference lies in their mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. This means they work slightly differently in your body, which may affect how you experience side effects like bloating. Understanding these differences can help you and your prescriber decide which might be more suitable for you during clinical assessment.
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.
How Mounjaro and Wegovy Work Differently
Mounjaro activates two hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual action may influence appetite regulation, gastric emptying speed, and how your body uses fat differently than Wegovy's single mechanism.
Wegovy activates GLP-1 only, which signals fullness to the brain and slows how quickly food leaves your stomach. Both mechanisms can cause temporary bloating or abdominal discomfort, especially during dose titration. The SURMOUNT-1 trial (Mounjaro) showed average weight loss of approximately 15–20.9% depending on dose, whilst the STEP-1 trial (Wegovy) showed approximately clinically studied weight loss at 68 weeks. Individual tolerance to gastrointestinal effects varies significantly between people and between medications. Your prescriber will assess which is more likely to suit your body's response based on your medical history.
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.
Which Is Right for You? A Prescriber Decision
Neither Mounjaro nor Wegovy can be recommended as "better" for bloating without knowing your individual health profile. Bloating occurs because both medications slow gastric emptying and regulate appetite signals—this is how they support weight loss. Some people experience bloating more with one medication than the other; others find it manageable or temporary as their body adjusts. Your GLP-1 weight loss calculator can help you explore potential weight loss projections, but the bloating question is best discussed with your prescriber during clinical assessment. They will take your full medical history, any previous medication responses, and current digestive health into account. If bloating becomes problematic, your prescriber can adjust the dose, pause escalation, or suggest a different medication. Never stop or change your dose without guidance. Both medications are prescription-only and require ongoing clinical support.
- 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?
Both can cause bloating, particularly during initial weeks or dose increases. Individual responses vary significantly. Some people experience more bloating with Mounjaro's dual mechanism; others tolerate it better. Clinical trials show both are generally well-tolerated, but side effects differ between individuals. Your prescriber can discuss your risk factors.
How long does bloating last with Mounjaro or Wegovy?
Bloating often improves after 2–4 weeks as your body adjusts to the medication. Slower dose titration may help. Staying hydrated, eating smaller meals, and gentle movement can help manage symptoms. If bloating persists beyond 4 weeks, contact your prescriber—dose adjustment may help.
Can I switch from Mounjaro to Wegovy if I'm experiencing bloating?
Possibly, but only with your prescriber's guidance. Switching medications requires a clinical decision and new assessment. Sometimes reducing your Mounjaro dose and staying on it longer before escalating reduces bloating. Switching is an option if side effects are intolerable, but there's no assures Wegovy will cause less bloating for you personally.
What's the difference between Mounjaro and Wegovy side effects in clinical trials?
Both showed similar gastrointestinal side effect rates in SURMOUNT and STEP trials. The most common side effects include nausea, diarrhoea, vomiting, and constipation—bloating falls within these digestive effects. Mounjaro's dual mechanism may affect some people differently, but trial data shows comparable tolerability overall.
How can my GP help if I'm bloated on Mounjaro or Wegovy?
Your prescriber can review your symptoms, adjust your dose timing or escalation schedule, recommend dietary changes (smaller, frequent meals), suggest over-the-counter remedies like peppermint tea or ginger, or switch medications if bloating is severe. Never self-adjust—always contact your healthcare provider first.
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.