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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Understanding Bloating and Mounjaro in the UK
Bloating is a common side effect reported by people taking Mounjaro (tirzepatide) in the UK. This happens because Mounjaro slows how quickly food moves through your stomach, which can cause temporary gas and abdominal discomfort. Bloating usually improves as your body adjusts to the medication, particularly as you move through dose titration stages. If bloating persists or significantly affects your daily life, your GP can offer practical management strategies or discuss whether continuing treatment is right for you.
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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 Causes Bloating and How It Changes Over Time
Mounjaro works by activating GIP and GLP-1 receptors, which slows gastric emptying — the rate at which food leaves your stomach. This delayed movement can trap gas, creating bloating and abdominal distension, especially after meals. The effect is usually most pronounced in the first 4–8 weeks of treatment and tends to reduce as your body adapts. During dose titration — when you progress from 2.5 mg through to 15 mg over several weeks — bloating may temporarily worsen when you increase doses, then improve again as your system adjusts. Some people experience bloating mainly after larger meals or certain foods, while others report mild, persistent discomfort.
- Bloating is classed as very common in clinical trials (affecting more than 1 in 10 people)
- It often improves significantly by weeks 8–12 as your body adapts
- Individual variation is substantial — some people experience minimal bloating
- Gastric effects typically diminish over time with continued use of the same dose
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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.
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Managing Bloating While Taking Mounjaro
If you're experiencing bloating on Mounjaro, practical steps can help reduce discomfort. Eat smaller, more frequent meals rather than large portions — this reduces the volume of food in your stomach at once. Avoid fizzy drinks, chewing gum, and foods known to produce excess gas (beans, cruciferous vegetables, high-fat foods). Drink plenty of water throughout the day, and try gentle movement like walking after meals to aid digestion. If bloating significantly impacts your quality of life or doesn't improve after 8–12 weeks, contact your GP. They can assess whether it's a normal adjustment effect or whether your treatment plan needs reviewing. Your prescriber may also discuss whether OTC remedies like simethicone could help, though always check with them first.
- 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 bloating on Mounjaro dangerous?
Mild to moderate bloating is not dangerous and is a normal, temporary side effect. However, severe, persistent abdominal pain — especially pain radiating to your back — could indicate pancreatitis, which is rare but serious. Seek immediate medical attention if you experience severe pain. For routine bloating, contact your GP if it doesn't improve after 8–12 weeks.
How long does Mounjaro bloating last?
Bloating typically improves as your body adapts within the first 4–12 weeks of starting Mounjaro or after a dose increase. For most people, gastric effects diminish significantly by week 12, though some mild bloating may persist. Individual timescales vary — some people adjust quickly, others more slowly. Your GP can advise if adjustment takes longer than expected.
Can I take over-the-counter remedies for Mounjaro bloating?
Simethicone (an anti-gas product) is sometimes suggested, but always discuss with your prescriber or GP first. They'll advise whether it's appropriate for you. Dietary changes — smaller meals, avoiding fizzy drinks and gas-producing foods — are typically the first-line approach and often more effective than medication.
Does bloating on Mounjaro mean I should stop the medication?
Bloating alone is not a reason to stop Mounjaro unless it's severely affecting your quality of life. Most people find it improves over time. However, if bloating is combined with other concerning symptoms, or if you're struggling, your GP or prescriber can review your treatment and discuss alternatives. They can also help distinguish between normal bloating and other digestive issues.
Is bloating on Mounjaro the same as on Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) slow stomach emptying, so bloating can occur with both. However, Mounjaro's dual GIP and GLP-1 mechanism may cause slightly different gastric effects than Wegovy's GLP-1-only action. Individual experiences vary considerably — some people tolerate one better than the other. Your GP can discuss this if you're considering switching.
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