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 Machine For Weight Loss: UK Prescription Options
When people search for the "best machine" for weight loss, they're often looking for effective solutions. In the UK, the most clinically effective weight management tools available are prescription medications — not machines. GLP-1 and GIP/GLP-1 receptor agonist injections like Mounjaro and Wegovy have shown significant results in clinical trials. These prescription weight loss medications work alongside diet and exercise to help eligible adults achieve meaningful weight loss. Understanding your options — whether through NHS weight management services or private prescribing — is the first step toward finding the right approach for your health goals.
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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 Prescription Weight Loss Medications
In the UK, three prescription medications are licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are the most commonly prescribed weight loss injections today.
Mounjaro is a dual GIP and GLP-1 receptor agonist administered once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks at maximum dose, alongside a reduced-calorie diet and increased physical activity. Wegovy is a GLP-1 receptor agonist also given once weekly, with average weight loss around 15% in clinical trials.
Both are prescription-only medicines requiring a clinical assessment. Eligibility typically includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Results vary significantly between individuals — some people respond better than others. Our GLP-1 weight loss calculator can help you explore projected outcomes at different doses based on clinical trial data.
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.
Accessing Weight Loss Medication in the UK
Prescription weight loss medication is available through two routes in the UK. NHS access is through specialist tier 3 and tier 4 weight management services — typically requiring a referral from your GP. Availability varies by region and ICB, with waiting lists often extending several months in many areas.
Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral and prescriptions can be issued more quickly.
To find out if prescription weight loss medication is right for you, speak with your GP. They can assess your BMI, health history, and weight-related conditions, and discuss whether medication alongside lifestyle changes would be beneficial. Use our free BMI calculator above to check your personal BMI before your consultation — it helps frame the conversation with your healthcare provider.
- 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.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription weight loss injections given once weekly, but Mounjaro activates two hormone pathways (GIP and GLP-1) while Wegovy activates one (GLP-1). Clinical trials show Mounjaro may support slightly greater average weight loss, though results vary individually. Both require clinical assessment before prescription. Your prescriber will advise which is more suitable for you.
Can I get prescription weight loss medication on the NHS?
Yes, prescription weight loss medications are available through NHS specialist weight management services (tier 3 and 4). You'll need a GP referral and an assessment by the specialist team. Availability varies significantly by region — some areas have waiting lists of many months. Private prescribing is also available without NHS referral.
How much weight can I expect to lose with prescription medication?
In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, and Wegovy around 15% — though individual results vary considerably. Weight loss depends on the dose, how your body responds, diet, exercise, and other factors. Your prescriber will discuss realistic expectations for your specific situation.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above are typically eligible. Those with a BMI of 27–29.9 may be eligible if they have weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
Do prescription weight loss injections work without diet and exercise changes?
No. These medications are most effective when combined with a reduced-calorie diet and increased physical activity. They support your efforts by helping reduce appetite and manage food cravings — they're not a replacement for lifestyle changes. Your prescriber will discuss the complete approach during your assessment.
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.