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
Free tracker included with every download this week
Medication to Help Lose Weight — Your UK Options
If you're looking for medication to help lose weight in the UK, you have several options available. Sustainable weight loss can be achieved through lifestyle changes alone, but prescription medications like GLP-1 injections (such as Mounjaro and Wegovy) are increasingly available to support weight management. Understanding what's available through the NHS, private providers, and how these options compare will help you make an informed choice with your GP about the best approach for your individual needs.
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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 Available in the UK
There are five main levels of weight loss support available to UK adults, often called the NHS weight management pathway. At tier 1, you can access free digital tools and community programmes—MyWeightCheck's free BMI calculator, weight converter, and GLP-1 weight loss calculator can help you assess your current health status and explore potential outcomes. Tier 2 involves primary care support through your GP, including behaviour change programmes and diet advice. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medication may be initiated. Tier 4 is bariatric surgery for severe obesity.
Prescription weight loss medications currently licensed in the UK include tirzepatide (Mounjaro), semaglutide (Wegovy), and liraglutide (Saxenda). These work by reducing appetite and supporting feeling fuller after smaller meals. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. Access through the NHS is via tier 3 specialist services (availability varies by region), whilst private options are available through online prescribing following a clinical assessment.
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.
How to Choose the Right Weight Loss Approach
The right weight loss medication or method depends on your individual circumstances. Consider: your current BMI (calculate yours with our free BMI calculator above), any existing health conditions, how much weight you want to lose, and your lifestyle. Lifestyle changes alone—including reduced-calorie diet and increased physical activity—work for many people and remain the foundation of sustainable weight loss.
Prescription medication is typically used alongside lifestyle changes, not instead of them. If you're interested in exploring medication options, start a conversation with your GP. They can assess your eligibility, discuss potential side effects, and refer you to appropriate services. Use our free progress tracker to monitor your weight loss journey regardless of which approach you choose. Remember, individual results vary significantly, and what works for one person may differ for another.
- 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 get weight loss medication on the NHS?
Yes. Weight loss medications are available through NHS tier 3 specialist weight management services if you meet eligibility criteria (BMI 30+ or 27+ with weight-related health conditions). Access varies significantly by region and waiting lists can be lengthy. Ask your GP for a referral to your local specialist weight management service.
What's the difference between Mounjaro and Wegovy?
Both are prescription-only once-weekly injections. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates one (GLP-1). Clinical trials showed Mounjaro and Wegovy produce comparable weight loss results—approximately 15–21% of body weight. Individual outcomes vary. A prescriber will assess which is most suitable for you.
How much weight can I expect to lose with medication?
Clinical trials showed weight loss averages of 15–21% of body weight over 68 weeks, though individual results vary significantly. Weight loss is achieved alongside a reduced-calorie diet and increased physical activity—medication alone is not enough. Our GLP-1 weight loss calculator can help you explore potential projections.
What are the side effects of weight loss medication?
Common side effects include nausea, constipation, diarrhoea, and stomach discomfort. These usually improve over time. Serious side effects are rare but can include pancreatitis. Your prescriber will discuss all potential side effects before you start treatment and monitor you throughout.
Do I need a prescription for weight loss medication in the UK?
Yes. All weight loss medications (Mounjaro, Wegovy, Saxenda) are prescription-only in the UK. You must have a clinical assessment from a UK-licensed prescriber before being prescribed. This ensures the medication is appropriate for your individual health circumstances.
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.