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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Diabetic Drugs for Weight Loss in the UK
Originally developed to help people with type 2 diabetes manage blood sugar, certain diabetic medications have proven highly effective for weight management in UK adults. Mounjaro (tirzepatide) and Wegovy (semaglutide) are now licensed specifically for weight loss in people with a BMI of 30 or above, or 27 or above with weight-related health conditions. These prescription medications work alongside a reduced-calorie diet and increased physical activity. Understanding your eligibility and how to access them is the first step toward effective weight management.
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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.
UK-Licensed Weight Management Medications
Three prescription-only medications are currently licensed in the UK for weight management and represent an important option within the weight loss medication nhs pathway:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist. Once-weekly injection, doses from 2.5 mg to 15 mg. Clinical trials showed average weight loss of approximately 15–21% of body weight alongside lifestyle changes.
- Wegovy (semaglutide) — a GLP-1 receptor agonist. Once-weekly injection, maximum dose 2.4 mg. Clinical evidence demonstrated around 14.9% average weight loss in trials at the highest dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist. Once-daily injection, maximum dose 3 mg. Longer-established option with proven effectiveness for glp-1 weight loss.
Eligibility for prescription weight loss uk treatment requires a BMI of 30 or above, or 27–29.9 with conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Individual results vary significantly. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, and our free BMI calculator to check where you currently stand.
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.
How to Access Weight Loss Medication in the UK
Access to these medications differs between NHS and private routes. NHS access is through specialist tier 3 weight management services, usually via GP referral, though regional availability and waiting times vary considerably. Private access is available through UK-licensed prescribers following an online clinical assessment — faster and does not require NHS referral, though involves a cost. Both routes require a thorough assessment to ensure the medication is appropriate for your individual health. Whichever route you choose, weight loss medication works best alongside behaviour change: a reduced-calorie diet, increased physical activity, and often support from a healthcare professional. Your GP can discuss which option is most suitable for your circumstances and help you explore eligibility.
- 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.
Are diabetic drugs safe for weight loss if I don't have diabetes?
Yes. Mounjaro and Wegovy were originally developed for diabetes but are now licensed specifically for weight management in people without diabetes. A prescriber will assess whether the medication is suitable based on your BMI and overall health, not diabetes status alone.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections, but Mounjaro has a higher maximum dose (15 mg vs 2.4 mg) and showed slightly higher average weight loss in trials. Clinical evidence suggests both are effective; individual response varies.
How quickly will I lose weight on these medications?
Clinical trials showed average weight loss of 14–21% of body weight over several months, but individual results vary significantly. Weight loss is gradual and typically becomes visible within the first 4–8 weeks. You'll likely lose more if you also follow a reduced-calorie diet and increase physical activity.
Can I get these medications on the NHS?
Yes, NICE has approved tirzepatide and semaglutide for NHS use through specialist weight management services. Access is via GP referral to tier 3 services. Availability and waiting times vary by region and local ICB commissioning, so your GP can advise whether NHS access is available in your area.
What are the main side effects of weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — most occur in the first few weeks and often improve over time. Serious side effects are rare but can include pancreatitis (severe stomach pain). A prescriber will review your medical history and any medications before prescribing and monitor you during 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.