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
Is Mounjaro Approved For Weight Loss In The UK?
Yes, Mounjaro (tirzepatide) is approved for weight loss in the UK. It's a prescription-only, once-weekly weight loss injection licensed by the MHRA for adults with obesity or overweight with weight-related health conditions. Unlike some weight loss injections, Mounjaro uses a dual mechanism — activating both GIP and GLP-1 hormone pathways — which may help reduce appetite and support weight management alongside diet and exercise. Clinical trials showed adults lost an average of 15–21% of their body weight, though individual results vary significantly. Access is available through NHS specialist weight management services or private online prescribing following a clinical assessment.
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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 Works For Weight Loss
Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist. This dual action is what sets it apart from other weight loss injections like Wegovy, which target GLP-1 alone. When injected, Mounjaro activates two natural hormone pathways in your body: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). These hormones help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. Mounjaro also slows gastric emptying — how quickly food leaves your stomach — though this effect typically reduces over time.
Clinical trial data: The SURMOUNT-1 trial showed that at the maximum dose of 15mg weekly, participants lost approximately 20.9% of their body weight on average over 72 weeks, alongside a reduced-calorie diet and increased physical activity. Weight loss was gradual and progressive, with most loss occurring between weeks 4 and 52. Use our GLP-1 weight loss calculator to see projected weight loss estimates at different Mounjaro doses based on your starting weight.
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 Eligibility And How To Access Mounjaro
To be eligible for Mounjaro in the UK, you must have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or previous heart disease. People of South Asian, Chinese, Black African, or Black Caribbean background may qualify at lower BMI thresholds due to higher health risks at lower weights.
Access routes: On the NHS, Mounjaro is prescribed through tier 3 specialist weight management services — you'll need a referral from your GP, and availability varies by region. Private access is available through UK-licensed online prescribers following a clinical assessment. Check your eligibility using our free BMI calculator, then discuss options with your GP or contact a private prescriber for assessment.
- 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 Mounjaro the same as Wegovy?
No. Both are prescription weight loss injections available in the UK, but they work differently. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates GLP-1 only. Clinical trials showed similar average weight loss outcomes (around 15–21% for Mounjaro, 15% for Wegovy), but individual results vary. Your prescriber will assess which is suitable for you.
Can I get Mounjaro on the NHS?
Yes, but availability is limited. NICE has approved tirzepatide (Mounjaro) for NHS use, but it's prescribed only through specialist tier 3 weight management services after GP referral. Waiting times and eligibility criteria vary significantly across different NHS regions. Your GP can advise whether you qualify and what's available locally.
What's the starting dose of Mounjaro?
The starting dose is 2.5mg once weekly. Your prescriber will increase the dose gradually every 4 weeks — moving through 5mg, 7.5mg, 10mg, 12.5mg, and up to 15mg as the maximum dose. Dose titration takes about 20 weeks to reach the highest dose if that's needed for you.
How quickly will I lose weight on Mounjaro?
Weight loss is gradual. Most people see initial changes within 4 weeks, with more significant losses between weeks 4 and 52. Average total weight loss is 15–21% of body weight over 72 weeks in clinical trials, but this varies widely between individuals. Mounjaro works best alongside a reduced-calorie diet and increased physical activity.
What if Mounjaro doesn't work for me?
Individual responses vary — some people lose more weight, others less. If you're not seeing results after 12 weeks at an adequate dose, your prescriber may adjust your dose, try a different medication (such as Wegovy), or discuss other weight management options. Always discuss concerns with your prescriber before stopping treatment.
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.