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 and Sulphur Burps — What You Need to Know
Sulphur burps (also called rotten egg burps) are a known side effect some people experience when taking Mounjaro (tirzepatide) for weight management. This happens because Mounjaro slows how quickly food leaves your stomach, which can create digestive gases. While the symptom is usually temporary and mild, understanding what to expect and how to access Mounjaro in the UK — whether through the NHS or privately — helps you make an informed decision about whether this prescription medication is right for you.
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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 Sulphur Burps Occur With Mounjaro — And Access Routes
Sulphur burps are caused by Mounjaro's mechanism of action. As a dual GIP and GLP-1 receptor agonist, tirzepatide slows gastric emptying — meaning food stays in your stomach longer. This can lead to fermentation and the production of hydrogen sulphide gas, creating the unpleasant rotten egg smell. The good news: this side effect is usually temporary, often reducing or disappearing after a few weeks as your digestive system adjusts.
Managing the symptom: eating smaller, more frequent meals; chewing food thoroughly; avoiding high-fat foods; staying hydrated; and taking a short walk after eating can all help. If sulphur burps persist beyond 8 weeks or become severe, discuss with your prescriber — dose adjustment or temporary pause may help.
In the UK, you can access Mounjaro through two main routes: NHS specialist weight management services (tier 3) and private prescription via online clinical assessment. NHS access involves a GP referral and assessment by a specialist team; private routes offer faster access but at personal cost.
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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.
UK Private Costs and Clinical Assessment Process
Private Mounjaro costs in the UK typically range from £150–£280 per month depending on dose and provider, with most people requiring a dose titration from 2.5 mg up to their maintenance dose over 16–20 weeks. You'll need an online consultation with a UK-licensed prescriber, who will review your medical history and BMI eligibility (BMI 30+, or 27+ with weight-related health conditions) before issuing a prescription to a GPhC-registered pharmacy. NHS access is free but often involves waiting lists of several months. Use our GLP-1 weight loss calculator to estimate potential weight loss at different Mounjaro doses alongside your cost considerations.
Before starting Mounjaro, your prescriber will check for contraindications like personal or family history of thyroid cancer, pancreatitis risk, or severe gastroparesis. Online consultations typically take 15–30 minutes and cost £15–£50. Once approved, your prescription goes to a registered UK pharmacy and is dispatched within 1–2 working days. Each Mounjaro KwikPen contains 4 weekly doses and must be refrigerated until use, then stored at room temperature for up to 30 days after opening. Calculate your BMI now using our free BMI calculator to confirm your eligibility 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.
Are sulphur burps a common side effect of Mounjaro?
Yes, sulphur burps (rotten egg burps) are a recognised side effect affecting some users, particularly in the first few weeks of treatment. They occur because Mounjaro slows stomach emptying, leading to fermentation of food. The symptom usually improves within 4–8 weeks as your body adjusts. They're not dangerous, just unpleasant.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs approximately £150–£280 per month depending on your dose and the provider. Starting dose (2.5 mg) is cheaper than maximum dose (15 mg). Costs may vary slightly between GPhC-registered pharmacies. NHS access is free but involves waiting lists and GP referral to specialist services.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is NICE-approved for NHS use within specialist tier 3 weight management services. You'll need a GP referral and assessment. NHS availability varies significantly by region (ICB), and waiting lists can be several months in many areas. Your GP can advise on local access.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials show Mounjaro may produce slightly greater weight loss (~21% vs ~15%), but results vary individually. Both are prescription-only and available via NHS or private routes in the UK.
How long does Mounjaro dose titration take?
Mounjaro dose titration typically takes 16–20 weeks. You start at 2.5 mg weekly, increasing by 2.5–5 mg every 4 weeks until reaching your target maintenance dose (usually 10–15 mg). Your prescriber adjusts based on your tolerance and response. Always stay on each dose for the full 4 weeks before escalating.
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.