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 Burn Fat? How It Works & UK Access
Mounjaro (tirzepatide) doesn't directly "burn" fat in the way exercise does, but it works through hormonal pathways that support weight loss. As a dual GIP and GLP-1 receptor agonist, it helps regulate appetite, reduce cravings, and support feeling fuller after smaller meals. In the UK, you can access Mounjaro through NHS specialist services or private prescription routes, with costs and eligibility varying significantly depending on which pathway you choose. This guide explains how it works, what it costs, and how to access it.
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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.
How Mounjaro Supports Weight Loss and Fat Loss
Mounjaro doesn't directly burn calories like cardio does. Instead, it works by activating two natural hormone pathways — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) — which together signal your body to reduce appetite and cravings. This makes it easier to maintain a calorie deficit, which is essential for fat loss.
When you create a sustained calorie deficit through reduced food intake (supported by Mounjaro) and increased physical activity, your body accesses stored fat for energy. The drug slows gastric emptying, meaning food stays in your stomach longer, which helps you feel satisfied for longer. Clinical trials show that people taking Mounjaro at the maximum 15 mg dose lost an average of around 20.9% of their body weight over 72 weeks — though individual results vary significantly and weight loss always requires lifestyle changes alongside medication.
Unlike your metabolism directly burning fat, Mounjaro creates the conditions where fat loss becomes easier to achieve through calorie deficit.
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.
Mounjaro Cost & Access in the UK
NHS access: Mounjaro is available through NHS specialist tier 3 and tier 4 weight management services, but only after NICE approval and GP referral. Availability varies dramatically by region — some ICBs have years-long waiting lists, whilst others have limited access. NHS prescription means minimal cost to you once prescribed.
Private access: Available through UK-licensed prescribers via online consultation (no waiting list). Private prescription costs typically range from £129 to £320+ per month depending on dose. The KwikPen device (4 pens per box) costs vary by provider. You'll need to pass a clinical assessment before prescription is issued. Private access is faster but significantly more expensive than NHS.
Use our GLP-1 weight loss calculator above to explore potential outcomes at different doses, and our BMI calculator to check your eligibility threshold.
- 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.
Does Mounjaro actually burn fat or just reduce appetite?
Mounjaro primarily works by reducing appetite and cravings through GIP and GLP-1 hormone activation. It doesn't directly "burn" fat in the metabolic sense. However, by making it easier to maintain a calorie deficit, it creates the conditions where your body accesses stored fat for energy. Fat loss still requires a sustained calorie deficit and lifestyle changes — Mounjaro makes that deficit easier to maintain.
How much does Mounjaro cost privately in the UK?
Private Mounjaro typically costs £129 to £320+ per month depending on the dose and provider. Starting doses (2.5–5 mg) are usually cheaper than maximum doses (10–15 mg). Costs cover the prescription and the KwikPen device. Always check with providers for current pricing, as costs vary. NHS prescription is free once you're referred to specialist services, but waiting lists can be lengthy.
Can I get Mounjaro on the NHS in the UK?
Yes, but access is limited. NICE has approved tirzepatide (Mounjaro) for NHS use within specialist tier 3/4 weight management services. You'll need a GP referral and clinical assessment. Availability varies significantly by region — some areas have long waiting lists, whilst others have restricted access. Your GP can advise whether NHS access is available in your area.
What's the difference between Mounjaro and Wegovy for fat loss?
Both are prescription weight loss injections licensed in the UK. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1-only agonist. Clinical trials suggest Mounjaro may produce slightly greater average weight loss (~21% vs ~15%), but individual results vary widely. Both work by reducing appetite and supporting calorie deficit. Both require prescription and clinical assessment.
Do I need a GP referral for private Mounjaro prescription?
No. You can access private Mounjaro through an online consultation with a UK-licensed prescriber without NHS referral. You'll complete a clinical assessment online, and if approved, receive a prescription dispensed by a GPhC-registered pharmacy. NHS access does require GP referral to specialist services, which is a different pathway altogether.
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.