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 Combined Pill for Weight Loss in the UK
There is no single "best" weight loss pill for everyone — the right option depends on your individual health, eligibility, and preferences. However, prescription weight management medications are now available in the UK for adults with obesity or overweight with health conditions. The most effective combined option is Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist that works on two hormone pathways simultaneously. This guide explains UK-licensed prescription options, how they work, and how to find out if you're eligible for weight management medication through the NHS or private prescription.
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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 Loss Medications and How They Work
Mounjaro (tirzepatide) is the only true "combined" weight loss medication available in the UK. It activates both GIP and GLP-1 hormone pathways, which may help regulate appetite, reduce cravings, and support feeling fuller after meals. Clinical trials showed participants lost an average of 15–21% of body weight alongside dietary changes and increased physical activity. Mounjaro is injected once weekly, starting at 2.5 mg and escalating up to 15 mg.
Wegovy (semaglutide) is a GLP-1 receptor agonist — a single-pathway medication. Clinical trials showed average weight loss of around 15% body weight. It's also injected once weekly and escalates from 0.25 mg to 2.4 mg.
Saxenda (liraglutide) is another GLP-1 option but requires daily injections rather than weekly. All three are prescription-only medicines requiring clinical assessment before prescription.
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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 Weight Loss Medication in the UK
You may be eligible for prescription weight loss treatment if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, or sleep apnoea). Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower weights.
NHS access: Referral to a specialist tier 3 weight management service through your GP, though regional waiting lists vary significantly. Private access: Online consultation with a UK-licensed prescriber, available without NHS referral. Use our free BMI calculator to check your starting point, and discuss your individual options with your GP or a licensed prescriber.
- 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?
Mounjaro is a dual GIP and GLP-1 agonist working on two hormone pathways, while Wegovy is a GLP-1 agonist only. Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21% vs ~15%), but both are effective. Individual results vary significantly. Your prescriber will recommend the best option based on your health profile.
Can I get weight loss medication on the NHS?
Yes, through specialist tier 3 weight management services if you're referred by your GP and meet eligibility criteria (BMI ≥30, or ≥27 with comorbidities). Availability varies by region and waiting lists can be lengthy. Private prescription is available without NHS referral through licensed online prescribers.
How much weight will I lose on prescription weight loss medication?
Clinical trials show average weight loss of 15–21% of body weight over approximately 68–72 weeks, but individual results vary significantly. Weight loss depends on the dose, how long you take the medication, and whether you follow a reduced-calorie diet and increase physical activity. Your GP can discuss realistic expectations for your situation.
Are weight loss pills or injections better?
Currently, the most effective UK-licensed weight loss treatments are injections (Mounjaro, Wegovy, Saxenda) rather than pills. Mounjaro is the only dual-action option. There are no GLP-1 pills licensed in the UK for weight management, though they may become available in future. Injections are typically more effective than traditional weight loss pills.
Do I need to change my diet if I take weight loss medication?
Yes. Weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They support appetite control and fullness, but don't work without lifestyle changes. Your prescriber will discuss dietary guidance, and our free weight loss calculator can help you estimate potential outcomes at different doses alongside lifestyle changes.
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.