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
Diabetes Medication For Weight Loss
Some diabetes medications are now prescribed for weight management in the UK, even for people without diabetes. The most well-known is semaglutide — originally developed to help manage type 2 diabetes blood sugar levels. Clinical trials showed it can help people lose significant weight. This guide explains how these medications work, what the evidence shows, and how to access them through the NHS or privately. Always consult your GP before considering any weight loss medication.
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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 Diabetes Medications Work For Weight Loss
Medications like semaglutide (Wegovy) and tirzepatide (Mounjaro) are GLP-1 and GIP/GLP-1 receptor agonists. Originally developed for type 2 diabetes, they activate natural hormone pathways that regulate appetite and blood sugar. When used for weight management, they may help reduce food cravings, increase feelings of fullness, and slow how quickly food leaves the stomach.
In the STEP clinical trials, semaglutide at the maximum 2.4 mg dose helped people lose an average of approximately 15% of their body weight over 68 weeks — alongside a reduced-calorie diet and increased physical activity. Tirzepatide (Mounjaro) showed average weight loss of 15–21% in the SURMOUNT trials. Individual results vary significantly.
These are prescription-only medicines in the UK. They are not suitable for everyone and require a clinical assessment before being prescribed.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Eligibility and How to Access Treatment in the UK
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
NHS access: Referral through your GP to a specialist tier 3 weight management service. Availability varies by region and waiting lists can be lengthy. Private access: Through an online consultation with a UK-licensed prescriber, available without NHS referral. Costs typically range from £129–£320 per month depending on the medication and dose. Calculate your BMI using our free BMI calculator above to understand your starting point.
- 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 semaglutide (Wegovy) the same as Ozempic?
Both contain semaglutide but are different products. Ozempic is licensed for type 2 diabetes at doses up to 2 mg. Wegovy is licensed specifically for weight management at doses up to 2.4 mg. In the UK, Ozempic is not licensed for weight loss — using it for weight loss would be off-label. Wegovy is the licensed weight management option.
Can I get diabetes weight loss medication on the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you, but you'll typically need a BMI of 30 or above (or 27+ with health conditions). Access varies significantly by region and waiting lists can be very long. Private online prescribing offers faster access without NHS referral.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a single GLP-1 agonist. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist. Clinical trials showed both help with weight loss — Mounjaro averaged 15–clinically studied weight loss, Wegovy around 15%. Both require weekly injections. Individual results vary, and a prescriber will advise which suits you.
How quickly will I lose weight on these medications?
Weight loss develops gradually as doses increase over several weeks. Most weight loss occurs in the later weeks of treatment. The NHS recommends losing 0.5–1 kg per week as a safe, sustainable rate. Results depend on diet, physical activity, starting weight, and individual metabolism. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
What are the main side effects of semaglutide and tirzepatide?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — often worse when doses increase. These usually improve over time. Serious side effects are rare but can include pancreatitis (severe stomach pain). Your prescriber will monitor you and discuss any concerns. Always report unexpected symptoms to your healthcare provider.
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.