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
Why Am I Feeling Bloated On Mounjaro?
Bloating is one of the most common side effects reported by people taking Mounjaro (tirzepatide), particularly in the first few weeks of treatment. It happens because Mounjaro slows how quickly food moves through your stomach and intestines, which can cause gas to build up and create that uncomfortable, full feeling. In most cases, bloating improves as your body adjusts to the medication, but understanding why it happens and knowing when to seek help from your GP makes the experience more manageable.
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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 Causes Bloating And Digestive Changes
Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways in your body. One of its effects is gastric slowdown: it delays how quickly food leaves your stomach and moves through your digestive system. This is actually part of how it helps with weight management, because slower digestion makes you feel fuller for longer. However, this delayed movement also means food sits in your stomach longer, gas can accumulate, and bloating can occur.
This side effect is very common — clinical trials and real-world reports show that many people experience bloating, abdominal discomfort, or that full feeling when starting Mounjaro or increasing their dose. The good news is that bloating typically improves within 2–4 weeks as your digestive system adapts to the medication.
- Bloating is listed as a "common" side effect of tirzepatide in UK prescribing information
- It often occurs alongside other digestive symptoms like constipation or indigestion
- Dose increases can temporarily worsen bloating before it settles again
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Managing Bloating: Practical Steps You Can Take
While you're waiting for your body to adjust, several practical strategies can help ease bloating. Eat smaller, more frequent meals instead of large portions — this reduces the burden on your slowed digestive system. Choose foods that are easier to digest: lean proteins, cooked vegetables, and whole grains rather than fatty or heavily processed foods. Stay well hydrated with water, as dehydration can worsen constipation and bloating. Gentle movement like walking after meals can also help stimulate digestion.
If bloating is severe or doesn't improve after 3–4 weeks, contact your GP. They may suggest temporary dose adjustments, recommend over-the-counter remedies like simethicone, or investigate whether another underlying condition is contributing. Track your symptoms using our free progress tracker — noting when bloating occurs and what triggers it can help your healthcare team provide better 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.
How long does bloating last on Mounjaro?
Bloating usually improves within 2–4 weeks as your body adjusts to tirzepatide. However, you may experience temporary bloating again if your dose is increased. If bloating persists beyond 4 weeks, contact your GP for guidance and potential adjustments.
Why does bloating happen with Mounjaro but not with Wegovy?
Both Mounjaro and Wegovy can cause bloating — Wegovy (semaglutide) is a single GLP-1 agonist while Mounjaro is a dual GIP/GLP-1 agonist. Some people find one causes less bloating than the other, but individual responses vary. Your GP or prescriber can help if side effects are troublesome.
What foods should I eat to reduce bloating on Mounjaro?
Choose smaller portions of easily digestible foods: skinless chicken, fish, cooked vegetables, white rice, and oatmeal. Avoid fried foods, high-fat meals, fizzy drinks, and artificial sweeteners which can worsen bloating. Eating slowly and chewing thoroughly also helps.
Is bloating a sign that Mounjaro isn't working for me?
No — bloating is a side effect of how tirzepatide works, not a sign of treatment failure. Weight loss and bloating can happen at the same time. Bloating typically improves as your body adapts, while the appetite-suppressing effects continue to support weight management.
When should I contact my GP about bloating on Mounjaro?
Contact your GP if bloating is severe, persistent after 4 weeks, accompanied by severe abdominal pain, or if it's affecting your daily life. They can assess whether dose adjustment, temporary pause, or additional support would help. Never stop Mounjaro without medical guidance.
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.