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
Mounjaro vs Wegovy for People with Diabetes
If you have type 2 diabetes and are considering weight loss medication, you may have heard about both Mounjaro and Wegovy. Both are prescription-only injections licensed in the UK for weight management, and both can help support weight loss alongside lifestyle changes. However, they work slightly differently and may suit different people. This guide compares them factually so you can understand the key differences before discussing options with your GP or prescriber.
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.
How Mounjaro and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. This dual mechanism may help regulate appetite and blood sugar more comprehensively. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. In clinical trials, Mounjaro showed slightly higher average weight loss — approximately 20.9% at the maximum 15 mg dose in the SURMOUNT-1 trial, compared to around 14.9% with Wegovy 2.4 mg in the STEP-1 trial. However, individual results vary significantly, and both work best alongside a reduced-calorie diet and increased physical activity.
- Mounjaro: dual mechanism (GIP + GLP-1), once weekly, maximum 15 mg dose
- Wegovy: single mechanism (GLP-1 only), once weekly, maximum 2.4 mg dose
- Both available as pre-filled injection pens
- Both slow gastric emptying and help reduce appetite
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.
Which Is Right for You? — A Prescriber Decision
Neither Mounjaro nor Wegovy is automatically "better" — suitability depends on your individual health, diabetes status, other medications, and how you respond. Your GP or prescriber will assess factors like kidney function, any previous pancreatitis, other diabetes medications you take, and whether you have contraindications to either. Both require a clinical assessment before prescription. If you're taking insulin or sulphonylureas, your prescriber may need to adjust those doses when starting either medication. Use our free GLP-1 weight loss calculator above to explore potential outcomes, and our BMI calculator to understand your starting point — then discuss both options with your prescriber to decide which fits your situation best.
- 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.
Can people with type 2 diabetes take Mounjaro and Wegovy?
Yes. Both are licensed for weight management in UK adults with type 2 diabetes or prediabetes who meet BMI thresholds. However, if you're already on insulin or certain diabetes medications, your prescriber may need to adjust doses. Always discuss with your GP or prescriber before starting either medication.
Which causes more weight loss — Mounjaro or Wegovy?
Clinical trials showed Mounjaro resulted in slightly higher average weight loss (around 21% body weight at maximum dose) compared to Wegovy (around 15%). However, individual results vary significantly. Some people respond better to one than the other. Your prescriber can discuss expected outcomes for your situation.
Is Mounjaro available on the NHS for diabetics?
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services for eligible adults. Access is through tier 3 specialist services, not standard GP prescription. Waiting times vary by region. Private access is available through online prescribing services.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist (two hormone pathways), while Wegovy activates only the GLP-1 pathway. This dual mechanism may explain slightly higher weight loss in trials, but both work similarly in terms of appetite reduction and how you feel after eating.
Do I need to stop diabetes medication if I start Mounjaro or Wegovy?
Not necessarily, but your prescriber may adjust doses — particularly if you're on insulin or sulphonylureas. These medications can lower blood sugar, so combining them with existing diabetes treatment requires careful monitoring. Always inform your prescriber of all current medications.
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.