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
Weight Loss Injections — What Are Your Options in the UK?
If you're considering an injection for losing weight, you have several options available in the UK. Weight loss injections are prescription-only medicines that can help support sustainable weight loss alongside lifestyle changes. But they're just one approach within a broader range of weight management strategies. This guide explores all your options — from free NHS support to prescription medications — to help you find the right path for your health.
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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
Weight loss in the UK is supported across four tiers of care. Tier 1 includes free self-help resources, digital tools, and community programmes — no GP referral needed. Tier 2 offers primary care support through your GP, including behaviour change programmes like the NHS Weight Loss Plan and free one-to-one coaching. Tier 3 provides specialist multidisciplinary weight management services through referral, where prescription weight loss medications may be considered. These include GLP-1 injections like Wegovy (semaglutide) and Mounjaro (tirzepatide), which help regulate appetite and support feeling fuller after smaller meals. Tier 4 involves bariatric surgery for severe obesity with significant health complications. Beyond injections, evidence-based approaches include calorie-controlled diets, increased physical activity, behaviour change support, and medical management of related conditions like type 2 diabetes.
- Tier 1: Free digital tools and community support
- Tier 2: GP-led behaviour change and coaching
- Tier 3: Specialist services with prescription medication options
- Tier 4: Bariatric surgery for severe obesity
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 method depends on your individual circumstances, health conditions, BMI, and preferences. Calculate your personal BMI using our free BMI calculator to understand where you sit on the NHS weight categories — this is often the starting point for determining eligibility. If you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure, you may be eligible for prescription weight loss support through NHS specialist services or private assessment. Most people benefit from combining approaches: dietary changes, physical activity, and behaviour support form the foundation, with medication added where clinically appropriate. Your GP can assess your individual situation, discuss your health goals, and recommend which tier of support is most suitable. There's no single "best" injection — individual results vary, 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.
What is the difference between weight loss injections available in the UK?
The main UK-licensed weight loss injections are Wegovy (semaglutide, once-weekly GLP-1 agonist) and Mounjaro (tirzepatide, once-weekly GIP+GLP-1 agonist). Both work by helping regulate appetite and support feeling fuller. Clinical trials showed different average weight loss percentages, but individual results vary significantly. Your prescriber will assess which is more suitable based on your health profile.
Can I get weight loss injections on the NHS?
Yes, weight loss injections are available through NHS tier 3 specialist weight management services for eligible adults. However, NHS availability varies by region, and waiting lists can be lengthy. Access requires referral from your GP to specialist services. Private online prescribing is also available for eligible adults following a clinical assessment through a UK-licensed prescriber.
Are weight loss injections suitable for everyone?
No. Injections are prescription-only and require a clinical assessment. You must not be pregnant, breastfeeding, or under 18. Certain medical conditions and medications may make them unsuitable. Your GP or prescriber will assess whether this approach is appropriate for your individual health situation before prescribing.
How much weight can I expect to lose with an injection?
Clinical trials showed average weight losses of 15–21% of body weight with Mounjaro and around 15% with Wegovy at maximum doses, achieved alongside reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more, some less. Weight loss is not assured, and results depend on adherence and lifestyle factors.
What should I do if I'm not sure which weight loss option is right for me?
Start by speaking with your GP. They can assess your health, BMI, and any weight-related conditions, then recommend the appropriate tier of support. Use our free BMI calculator and weight loss calculator to understand your starting point and projected outcomes. Your GP can then guide you toward NHS services or discuss private options based on your individual needs.
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.