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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Mounjaro Bloating Relief vs Wegovy — What's the Difference?
Bloating is a common side effect when starting Mounjaro or Wegovy, but the two medications work differently and may affect your digestive comfort in different ways. Both are prescription-only GLP-1 medications licensed in the UK for weight management, yet they have distinct mechanisms that can influence how your body responds. Understanding these differences — and knowing that individual experiences vary — helps you and your GP or prescriber make an informed decision about which treatment might suit you better. This guide compares both medications factually so you can discuss your options with a healthcare professional.
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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) is a dual GIP and GLP-1 receptor agonist. This dual mechanism means it activates two natural hormone pathways in your gut, which may contribute to bloating in different ways than a single-pathway medication. The GIP component works alongside GLP-1 to regulate appetite and glucose control. Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating a single hormone pathway.
In the SURMOUNT-1 clinical trial, Mounjaro users reported nausea, constipation, and diarrhoea as very common side effects. In the STEP-1 trial for Wegovy, similar gastrointestinal side effects were reported, though the exact rates differed slightly. Bloating and stomach distension are often related to how quickly your gut processes food — a process both medications slow intentionally. Neither trial specifically highlighted bloating as a primary distinguishing factor between the two.
The key difference: Mounjaro's dual action may affect your digestion more broadly, while Wegovy's single GLP-1 pathway provides a more targeted effect. Your individual response depends on your unique digestive system and how your body tolerates each mechanism.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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Dose Titration, Bloating, and Suitability
Both medications are started at low doses and increased gradually — a process called dose titration — to allow your body to adjust and minimise side effects like bloating. Mounjaro begins at 2.5 mg weekly and escalates up to 15 mg over 16+ weeks. Wegovy starts at 0.25 mg and reaches a maximum of 2.4 mg over 17+ weeks.
Slower titration often means less severe bloating. Some people find their bloating improves naturally as their body adapts over weeks. Others need to adjust their diet — eating smaller, more frequent meals and staying hydrated can help. A prescriber may also slow your dose increases if bloating is bothersome.
Neither medication is universally better for bloating relief. Your GP or prescriber will assess your medical history, current health conditions, and preferences to recommend which suits you. Both require a UK prescription and clinical assessment before starting. Try our free GLP-1 weight loss calculator to explore projected results with either medication, and use the BMI calculator to check your current health baseline.
- 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 doesn't show clear superiority for either. Both commonly cause bloating, nausea, and constipation. Individual experiences vary significantly. Some people find Mounjaro's dual mechanism suits them better; others prefer Wegovy's single pathway. Your prescriber will help choose based on your personal medical profile and tolerability.
How long does bloating last on Mounjaro or Wegovy?
Bloating often improves within 2–4 weeks as your body adjusts to the medication. Slower dose titration — staying on lower doses longer — can help. Eating smaller meals, drinking plenty of water, and increasing fibre gradually may ease symptoms. Persistent bloating should be discussed with your GP, as dose adjustments or alternative medications may be suitable.
Can I switch from Wegovy to Mounjaro if I have bloating?
Potentially, yes — but any switch must be managed by your prescriber. There's no direct conversion between the two; your prescriber would likely start you on Mounjaro's lowest dose and titrate up. Switching doesn't assures bloating relief, as both medications affect digestion. Discuss your concerns with your GP before making changes.
Is bloating a sign Mounjaro or Wegovy isn't working?
No. Bloating is a common side effect, not a sign of treatment failure. In fact, many people experience bloating whilst losing weight successfully. Bloating and weight loss can happen simultaneously. If you're concerned about side effects, talk to your prescriber — they may adjust your dose or offer practical strategies to manage discomfort.
Which medication is easier on the stomach, Mounjaro or Wegovy?
Neither has a clear advantage from trial data. Tolerability depends entirely on your individual digestive system, body composition, eating habits, and dose. Some people tolerate Mounjaro better; others find Wegovy gentler. Your prescriber will consider your medical history and previous medication responses to guide the best choice for you personally.
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