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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Medication To Lose Weight: Your UK Options
Weight loss medication is one tool available in the UK for managing excess weight, but it's not the only option. Whether you're looking for NHS support, prescription treatment, or lifestyle-based approaches, understanding the full range of weight loss methods available can help you make an informed decision with your GP. This guide explores medication alongside other evidence-based options designed to support sustainable weight loss across the UK health system.
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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.
Weight Loss Options In The UK: A Complete Overview
When considering medication to lose weight, it's important to understand the full spectrum of options available. The NHS organises weight management through a four-tier system, ensuring the right level of support matches your individual needs.
Tier 1: Self-help and community support — free resources including digital tools, apps, and local weight loss programmes. This is where most people start their weight loss journey.
Tier 2: Primary care interventions — structured support from your GP practice, including the NHS Weight Loss Plan and behaviour change coaching.
Tier 3: Specialist services — multidisciplinary weight management clinics run by NHS specialists. Prescription medications, including GLP-1 medications like Wegovy and Mounjaro, may be offered here following clinical assessment.
Tier 4: Surgical options — bariatric surgery for severe obesity with significant health complications.
Prescription weight loss medication is typically considered after lifestyle changes have been attempted, and eligibility depends on BMI and weight-related health conditions. Our GLP-1 weight loss calculator can help you estimate potential outcomes with medication, though results vary between individuals.
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.
Choosing The Right Approach For You
The best weight loss approach depends on your personal circumstances, health status, and goals. Consider these factors: your current BMI (calculate this using our free BMI calculator), whether you have weight-related health conditions like type 2 diabetes, how much lifestyle support you've already tried, and what fits realistically into your life.
Starting with lifestyle changes remains the foundation of sustainable weight loss in the UK — a reduced-calorie diet and increased physical activity typically lead to 0.5–1 kg loss per week. Prescription medication may be recommended if lifestyle changes alone haven't been effective, or if you have a BMI of 30 or above, or 27 or above with health complications.
Your GP is the best first point of contact. They can assess your individual situation, discuss NHS versus private routes, and help you understand which tier of support is most appropriate 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.
What is the safest way to lose weight in the UK?
The NHS recommends losing weight at a rate of 0.5–1 kg per week through a combination of reduced-calorie diet and increased physical activity. Starting with Tier 1 and Tier 2 support (self-help and primary care) is typically safest. Your GP can assess whether additional support or prescription medication is appropriate for your individual health.
Can I get weight loss medication on the NHS?
Yes, weight loss medications including Mounjaro (tirzepatide) and Wegovy (semaglutide) are available through NHS specialist tier 3 weight management services. Access requires referral from your GP and assessment by specialist clinicians. NHS availability varies significantly by region — some areas have long waiting lists.
What prescription weight loss medications are available in the UK?
Licensed prescription medications include Mounjaro (tirzepatide, up to 15 mg weekly), Wegovy (semaglutide, up to 2.4 mg weekly), and Saxenda (liraglutide, up to 3 mg daily). These are GLP-1 or GIP/GLP-1 receptor agonists. All are prescription-only and require a clinical assessment before being prescribed.
How do I know if weight loss medication is right for me?
Eligibility for prescription weight loss medication typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Your GP can assess whether medication is appropriate and whether NHS or private routes best suit your circumstances.
How much weight can I expect to lose with medication?
Clinical trials show average weight losses of 15–21% of body weight with GLP-1 and GIP/GLP-1 medications, though results vary significantly. Weight loss works best when combined with reduced-calorie diet and increased physical activity. Our weight loss calculator provides estimated projections, but individual outcomes depend on many factors including adherence and personal metabolism.
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.