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
Bloating With Mounjaro — Cost, Access & What to Expect
Bloating is one of the most commonly reported side effects of Mounjaro (tirzepatide) in the UK, affecting many people during the early weeks of treatment. Understanding why this happens, how long it typically lasts, and what your options are for managing it — along with knowing how to access this prescription medication in the UK — can help you make an informed decision. Whether you're considering Mounjaro through the NHS or exploring private prescription routes, this guide covers the real costs involved and what the access process looks like in practice.
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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.
Mounjaro Bloating & Digestive Side Effects
Bloating and digestive discomfort are very common in the first 4–8 weeks of Mounjaro treatment. This happens because tirzepatide slows how quickly food moves through your stomach (gastric emptying), which can cause gas, bloating, and constipation or diarrhoea as your body adjusts. Most users find these symptoms improve significantly by week 8–12 as your digestive system adapts, though some people experience them intermittently at higher doses.
- Nausea and vomiting typically decrease after the first month
- Constipation or diarrhoea may persist longer — drinking more water and increasing fibre gradually helps
- Bloating often improves when you eat smaller, more frequent meals
- Gas and indigestion are listed as very common side effects in clinical trials
If bloating is severe or persistent beyond 12 weeks, your prescriber may suggest staying at your current dose longer before increasing, or may recommend dose interval changes. This is why regular communication with your healthcare provider matters — they can adjust your Mounjaro KwikPen dosing schedule if needed.
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.
UK Prescription Access & Real Costs for Mounjaro
NHS access: NICE has approved tirzepatide for use within NHS specialist weight management services, but access is limited to tier 3/4 services through referral from your GP. Many areas have significant waiting lists, and regional availability varies considerably. Private prescription costs range from approximately £129–£320 per month depending on your current dose, with higher doses (10mg, 15mg) costing more than starter doses (2.5mg, 5mg). Online consultations with UK-licensed prescribers typically cost £40–£60 and are required before a private prescription is issued. Your GP can discuss which route might suit you best, and many people find private prescription a faster option where NHS waiting times are lengthy.
Accessing Mounjaro privately involves an online consultation with a UK-licensed prescriber who will assess your eligibility based on BMI, medical history, and current medications. If approved, your prescription is dispensed by a GPhC-registered pharmacy. Factor in the ongoing cost of the medication itself plus annual GP check-ups if using the private route — most private prescribers recommend annual health reviews. You can track your progress and side effects using our free progress tracker to share with your healthcare provider. The full UK prescription route (NHS or private) requires ongoing medical supervision, regular weight monitoring, and lifestyle changes alongside the medication for best results.
- 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 when starting Mounjaro?
Most people experience peak bloating and digestive discomfort in weeks 2–6, with significant improvement by weeks 8–12 as the body adapts. Some bloating may return when doses increase, but it typically settles within 1–2 weeks. Eating smaller meals, staying hydrated, and increasing fibre gradually all help during this adjustment period.
What's the cost difference between NHS and private Mounjaro in the UK?
NHS access is free at point of use through specialist services (if you can access it — waiting lists vary by region). Private prescription costs range from £129–£320 per month depending on dose, plus an initial online consultation fee of £40–£60. NHS waiting times are often 6–18 months, while private access is typically available within days to weeks.
Can my GP prescribe Mounjaro privately on the NHS?
Most GPs do not prescribe Mounjaro for weight management on the NHS — it's managed through specialist tier 3/4 weight management services following referral. However, your GP can refer you to these services or discuss private prescription options with you. Some GPs may support ongoing monitoring if you obtain a private prescription.
Do I need ongoing GP appointments if I use private Mounjaro?
Yes, most private prescribers recommend annual health check-ups and ongoing monitoring, particularly to review blood pressure, kidney function, and diabetes risk (if relevant). Your GP can support this monitoring even if they're not prescribing the medication. Regular check-ins ensure the medication remains safe and effective for you.
Does bloating on Mounjaro mean the medication isn't working?
No — bloating is a side effect of how tirzepatide works, not a sign of failure. In fact, some digestive symptoms (like reduced appetite and early fullness) are part of the mechanism that supports weight loss. Clinical trials show weight loss occurs even when people experience these initial side effects. The side effects typically improve while weight loss benefits continue.
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.