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
How Mounjaro Supports Fat Loss in the UK
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection licensed in the UK for adults with obesity or overweight with weight-related health conditions. In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight alongside diet and exercise. This guide explains how Mounjaro works for fat loss, NHS eligibility criteria, and how to access it through the UK healthcare system. Our free GLP-1 weight loss calculator can help you estimate potential results at different doses.
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.
NHS Eligibility and NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for weight management within NHS specialist services. You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, or Black Caribbean adults, eligibility may start at BMI 27.5 or above due to higher health risks at lower weights.
Access is typically through tier 3 specialist weight management services following a referral from your GP. MHRA monitors Mounjaro with additional safety surveillance. Clinical data shows Mounjaro's dual GIP and GLP-1 mechanism helps reduce appetite and support sustainable fat loss when combined with a reduced-calorie diet and increased physical activity. Doses escalate from 2.5 mg to a maximum of 15 mg weekly over 20+ weeks.
Check your personal BMI using our free BMI calculator to understand where you stand against NHS thresholds.
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.
NHS vs Private Access Routes in the UK
NHS route: Referral to tier 3 specialist weight management services (varies significantly by region and ICB). NHS provision is evidence-based and free, but waiting lists can be lengthy. Private route: Available through GPhC-registered online pharmacies following a clinical assessment by a UK-licensed prescriber, without needing NHS referral. Access is faster but involves cost. Both routes require a prescription; Mounjaro is never available over-the-counter. Your GP can advise on NHS availability in your area. Track your weight loss progress with our free progress tracker once you begin treatment.
- 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 does Mounjaro help with fat loss?
Mounjaro is a dual GIP and GLP-1 receptor agonist that mimics natural hormones controlling appetite. It helps reduce hunger signals, increase feeling of fullness, slow stomach emptying, and support better fat utilisation. Combined with a reduced-calorie diet and physical activity, clinical trials showed average fat loss of 15–21% body weight over 72 weeks.
Am I eligible for Mounjaro on the NHS?
You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related conditions like diabetes or high blood pressure. Lower thresholds apply for South Asian, Chinese, Black African, or Black Caribbean adults. Access is through tier 3 specialist services via GP referral. Availability varies by region.
What's the difference between Mounjaro and Wegovy for fat loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is GLP-1-only. Clinical data suggests Mounjaro may achieve slightly higher average fat loss (up to 20.9%), but individual results vary significantly. Both are prescription-only and require clinical assessment.
How long does it take to see fat loss results with Mounjaro?
Most people see measurable weight changes within 4–8 weeks, though individual timelines vary. Mounjaro doses escalate every 4 weeks from 2.5 mg to 15 mg. Results are best achieved with consistent reduced-calorie diet, regular physical activity, and adherence to weekly injections.
What's the weekly weight loss injection process like?
Mounjaro is a once-weekly KwikPen self-injection (stomach, thigh, or upper arm). Each pen contains 4 weekly doses. You inject at the same day each week. Side effects (nausea, diarrhoea) often reduce over time. Your prescriber monitors progress and adjusts doses based on your response and tolerability.
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.