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
Does Mounjaro Make You Gassy?
Gas and bloating are common side effects reported by people taking Mounjaro (tirzepatide) in the UK. These digestive symptoms typically occur early in treatment as your body adjusts to the medication, and often improve within the first few weeks. Understanding what to expect, how long symptoms last, and your options for accessing Mounjaro through the NHS or privately can help you make an informed decision about weight management. Our GLP-1 weight loss calculator can help you explore potential outcomes with tirzepatide treatment.
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.
Why Does Mounjaro Cause Gas and Bloating?
Gas, bloating, and indigestion occur because Mounjaro (tirzepatide) slows how quickly food moves through your digestive system—a process called delayed gastric emptying. This mechanism helps you feel fuller for longer, but it can cause temporary digestive discomfort.
- Why it happens: The medication mimics a natural hormone (GIP and GLP-1) that regulates appetite and digestion
- When it starts: Often within the first week of injections
- When it improves: Most people find gas and bloating reduce after 2–4 weeks as the body adapts
- Severity: Can range from mild bloating to noticeable gas, depending on individual response and dose
These are among the most frequently reported side effects in clinical trials and NHS guidance on tirzepatide. Managing diet and staying hydrated often helps ease symptoms during the adjustment period.
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.
Accessing Mounjaro in the UK: NHS vs Private Cost
NHS access: Mounjaro is available through specialist tier 3 weight management services, usually following GP referral. However, NHS availability varies significantly by region, and waiting lists can be several months. Your GP can advise whether you meet eligibility criteria (BMI 30 or above, or BMI 27+ with weight-related health conditions).
Private prescription: Many UK adults access tirzepatide privately through online consultations with UK-licensed prescribers, with costs ranging from approximately £130–£300 per month depending on dose. A clinical assessment is required before prescription. Our BMI calculator can help you check your starting point for weight management discussions with a healthcare provider.
Online consultation process: Private prescribing involves completing a health questionnaire, having your eligibility assessed by a UK-licensed doctor or pharmacist, and—if approved—receiving a prescription dispensed by a GPhC-registered pharmacy. Delivery typically takes 2–5 working days. This route offers faster access than NHS pathways but comes at out-of-pocket cost. Both routes require an ongoing relationship with your prescriber for dose monitoring and side effect management.
- 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 from Mounjaro last?
Most people experience peak bloating in the first 1–2 weeks, with significant improvement by week 3–4 as the body adjusts. Some mild gas may persist longer, especially after starting a new dose, but typically becomes manageable. If severe bloating continues beyond 4 weeks, discuss this with your prescriber—dietary adjustments or dose timing changes may help.
Can I reduce Mounjaro bloating without stopping the medication?
Yes. Eating smaller, frequent meals; chewing food slowly; staying hydrated; avoiding high-fat foods; and increasing fibre gradually can all reduce gas and bloating. Some people find ginger tea or peppermint helpful. Never stop or reduce your dose without speaking to your prescriber first.
How much does Mounjaro cost privately in the UK?
Private costs typically range from £130–£300 per month depending on your dose (starting at 2.5 mg, up to 15 mg maximum). This is the medication cost only and does not include the online consultation fee, which varies by provider. NHS access is free but involves specialist referral and often longer waiting times.
Do I need a prescription for Mounjaro in the UK?
Yes. Mounjaro is prescription-only in the UK. Access is either through your NHS GP and specialist weight management services, or through a private online consultation with a UK-licensed prescriber. You cannot buy it without a valid UK prescription.
Is bloating a reason to stop Mounjaro?
Bloating alone is not usually a reason to stop, as it typically improves within weeks. However, if you experience severe, persistent abdominal pain; signs of pancreatitis; or symptoms that concern you, contact your prescriber immediately. They can adjust your dose, timing, or offer other support to help you continue safely.
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.