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
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Wegovy for Diabetes: How It Compares to Mounjaro
Wegovy (semaglutide) is a prescription-only GLP-1 receptor agonist injection licensed in the UK for weight management in adults with type 2 diabetes or prediabetes who meet eligibility criteria. If you're considering weight loss medication for diabetes, you may have heard comparisons with Mounjaro (tirzepatide), another recently approved option. Both are once-weekly injections, but they work differently and have distinct clinical trial evidence. Understanding the differences can help you discuss the right option with your GP or a licensed prescriber. This guide compares the two medications factually, focusing on mechanism, evidence, eligibility, and access in the UK.
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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.
Mechanism, Clinical Evidence, and Key Differences
Wegovy (semaglutide) is a single-mechanism GLP-1 receptor agonist — it activates one hormone pathway to reduce appetite, slow stomach emptying, and improve blood sugar control. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, activating two hormone pathways simultaneously. This dual mechanism is the fundamental difference between the two medications.
Clinical trial evidence shows different weight loss outcomes: STEP-1 trial data demonstrated that Wegovy at 2.4 mg achieved average weight loss of approximately 14.9% of body weight over 68 weeks in adults with obesity or overweight with weight-related conditions. SURMOUNT-1 trial data showed Mounjaro at 15 mg achieved approximately 20.9% average weight loss over 72 weeks. However, individual results vary significantly, and both require a reduced-calorie diet and increased physical activity to be effective. Both medications also improve blood sugar control in people with type 2 diabetes or prediabetes, though this is measured through different metabolic markers.
- Wegovy: GLP-1 only, longer clinical history in weight management
- Mounjaro: Dual GIP+GLP-1, newer to UK weight loss market, higher average weight loss in trials
- Both: Once-weekly injections, prescription-only, require clinical assessment
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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.
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Eligibility, Access, and Next Steps in the UK
Both Wegovy and Mounjaro require similar eligibility criteria in the UK: a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (including type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to higher metabolic risk at lower weights.
Access varies: NHS prescription through specialist tier 3 weight management services (with potential waiting lists), or private prescription following online clinical assessment with a UK-licensed prescriber. Your GP can assess your individual health and refer you to specialist services, or you can pursue private assessment. Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different doses, and our BMI calculator to check whether you may meet eligibility criteria. Which medication suits you best depends on your medical history, current medicines, and individual factors — only a prescriber can determine this after 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 Wegovy effective for type 2 diabetes weight loss?
Yes, clinical trials show Wegovy helps with weight loss and improves blood sugar control in adults with type 2 diabetes. Average weight loss is around 15% of body weight, though individual results vary. It works alongside diet and exercise changes.
Which is better for diabetes — Wegovy or Mounjaro?
Neither is objectively "better" — suitability depends on your individual health, medications, and response. Mounjaro showed slightly higher average weight loss in trials (21% vs 15%), but Wegovy has longer clinical use. A prescriber will assess which is appropriate for you.
Can I get Wegovy on the NHS for diabetes?
Potentially yes, through specialist NHS tier 3 weight management services if you meet eligibility criteria (BMI ≥30 or ≥27 with conditions like diabetes). However, availability varies by region and waiting lists can be long. Your GP can assess referral eligibility.
How long does Wegovy take to work for diabetes?
Weight loss typically begins within 2–4 weeks but continues over months. Most clinical benefit was measured at 68 weeks in STEP trials. Blood sugar improvements may be noticed earlier. Consistency with injections and lifestyle changes is essential.
What are the main side effects of Wegovy for diabetes?
Very common: nausea, diarrhoea, constipation, vomiting, and abdominal pain — especially when starting or increasing doses. Most improve over time. Serious side effects are rare but include severe stomach pain (pancreatitis) and gallbladder issues. Always report persistent symptoms to your prescriber.
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.