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 Weight Loss and Muscle Gain Diet in the UK
Losing weight while maintaining muscle requires the right combination of diet, exercise, and sometimes medical support. If you're looking for the best weight loss approach in the UK, you'll find several options available—from lifestyle changes to prescription weight management medication. This guide covers evidence-based dietary strategies, how prescription weight loss injections work, and how to find out if you're eligible for treatment through the NHS or private routes. Everyone's situation is different, so it's worth understanding all your options before deciding on the best path forward.
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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.
Prescription Weight Loss Medication Available in the UK
For adults struggling with weight management, prescription weight loss medications are now available in the UK alongside diet and exercise. Three medications are currently licensed for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 hormone pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical trials showed average weight loss of approximately 15% of body weight.
- Saxenda (liraglutide) — a daily GLP-1 injection, typically producing modest weight loss when combined with lifestyle changes.
These are prescription-only medicines requiring clinical assessment. They work best alongside a reduced-calorie diet and increased physical activity—not as replacements for healthy habits. Individual results vary significantly based on dose, adherence, and personal health factors. To understand your potential outcomes, try our free GLP-1 weight loss calculator, which can help you explore projected results at different doses.
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.
NHS Access vs Private Options — Finding Out If You're Eligible
In the UK, there are two routes to access prescription weight loss medication: NHS specialist services and private prescribing.
NHS route: Your GP can refer you to a tier 3 specialist weight management service if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Eligibility varies by region, and waiting lists can be lengthy. Contact your GP surgery to ask about local services.
Private route: Adults can access prescription weight loss treatment through UK-licensed online prescribers following a clinical assessment. This option doesn't require an NHS referral but involves private costs.
Check your eligibility: Use our free BMI calculator above to see where you fall on the UK NHS categories. Your GP can provide personalised advice about whether medication is suitable for you.
- 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.
Can I lose weight and build muscle at the same time?
Yes, though it's challenging. A modest calorie deficit (300–500 kcal/day) combined with strength training can support both fat loss and muscle gain, especially if you're new to exercise. High protein intake (1.6–2.2g per kg body weight) is essential. However, this process is slower than focusing on weight loss alone. Your GP or a registered dietitian can provide a personalised plan.
What's the best diet for weight loss in the UK?
Evidence supports several approaches: Mediterranean diet (strong cardiovascular benefits), calorie deficit of 500 kcal/day (for ~0.5kg/week loss), and higher protein intake to preserve muscle. The "best" diet is one you can stick with long-term. NHS Weight Loss Plan offers free support. For weight management UK, consistency matters more than the specific diet type.
How do GLP-1 weight loss injections work?
GLP-1 medications like Wegovy and Mounjaro mimic natural gut hormones that regulate appetite and blood sugar. They reduce hunger signals, help you feel fuller on smaller portions, and slow stomach emptying. They work best alongside a reduced-calorie diet and exercise—they're not a replacement for lifestyle changes. Results vary between individuals.
How long does it take to see weight loss results?
Most people notice changes within 4–8 weeks of starting lifestyle changes. With prescription weight loss medication, noticeable effects typically appear after 2–4 weeks on therapeutic doses. The NHS recommends losing 0.5–1kg per week for sustainable results. gradual weight management isn't always healthier—consistency over time is more effective.
Do I need a referral to access weight loss medication in the UK?
Through the NHS, yes—your GP must refer you to specialist tier 3 weight management services. Through private prescribing services, no referral is needed, though you'll require a clinical assessment from a UK-licensed prescriber. Both routes require an assessment to confirm the medication is safe and appropriate for you.
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.