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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Best GLP-1 Supplement For Weight Loss In The UK
GLP-1 medications are not supplements — they are prescription-only medicines that may help support weight loss when used alongside lifestyle changes. If you're looking for weight management uk options, the two main GLP-1 medications licensed in the UK are Wegovy (semaglutide) and Mounjaro (tirzepatide). Understanding how they work, who qualifies, and what evidence supports their use is essential before speaking to your GP or a licensed prescriber about whether they might be right for you.
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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.
GLP-1 Medications For Weight Loss: The Key Options
GLP-1 receptor agonist medications are not supplements — they are prescription-only medicines that activate natural hormone pathways in the body. The two main options licensed for weight loss in the UK are:
- Wegovy (semaglutide) — a once-weekly injection approved for weight management. Clinical trials showed participants lost an average of around 15% of their body weight over 68 weeks, though individual results vary significantly.
- Mounjaro (tirzepatide) — a once-weekly injection with a dual GIP and GLP-1 mechanism. SURMOUNT trial data showed average weight loss of 15–21% depending on dose, alongside a reduced-calorie diet and increased physical activity.
Both are prescription-only and require clinical assessment before being prescribed. Access through NHS weight loss services varies by region, whilst private prescribing is available through online consultations with UK-licensed prescribers. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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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.
Who Qualifies For GLP-1 Weight Loss Medication?
Eligibility for prescription weight loss uk medications depends on BMI and health factors. You may qualify if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds due to higher health risks at lower weights. Your GP can assess whether you meet NHS weight loss criteria, or you can have a private clinical assessment online. Use our free BMI calculator above to check your current BMI and understand where you stand in relation to eligibility guidelines.
- 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 GLP-1 a supplement or a prescription medication?
GLP-1 medications like Wegovy and Mounjaro are prescription-only medicines, not supplements. They require a prescription from a UK-licensed prescriber and a clinical assessment to confirm they are appropriate for you. They are injectable medications that activate natural hormone pathways to help reduce appetite and support weight loss alongside dietary and lifestyle changes.
How much weight can you lose with GLP-1 medication?
Clinical trials showed average weight loss of 15–21% of body weight depending on the medication and dose used. However, individual results vary significantly. Weight loss is achieved alongside a reduced-calorie diet and increased physical activity — medication alone is not effective. Your GP or prescriber can discuss realistic expectations based on your personal health situation.
Can I get GLP-1 weight loss medication on the NHS?
Yes, GLP-1 medications including semaglutide (Wegovy) and tirzepatide (Mounjaro) are available through NHS specialist tier 3 weight management services in some areas. However, availability and waiting times vary significantly by region. You can ask your GP for a referral to local weight management services, or access private prescribing through online consultations with UK-licensed prescribers.
What is the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes management (doses up to 2 mg) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version at higher doses (up to 2.4 mg weekly). Using Ozempic for weight loss would be off-label use. Always ask your prescriber which medication and indication they are prescribing.
Are there side effects with GLP-1 weight loss medications?
Yes, common side effects include nausea, diarrhoea, constipation, and vomiting — especially when starting or increasing doses. These often reduce over time. Serious side effects are rare but can include severe stomach pain (pancreatitis) or gallbladder problems. Your prescriber will discuss all risks and benefits before you start, and you should report any concerning symptoms to your GP or healthcare provider immediately.
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.