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: Before And After Results In The UK
Weight loss injections are prescription medications that can support significant weight management when combined with lifestyle changes. In the UK, several options are available through both NHS and private prescribing. This guide explains how these medications work, what clinical evidence shows, who is eligible, and how to access them. Individual results vary considerably depending on dose, adherence, diet, and physical activity. If you're considering prescription weight management options, speaking with your GP is the first step.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Injections: What The Evidence Shows
Three prescription weight loss injections are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are not cosmetic injections—they are medications that work by activating hormonal pathways that regulate appetite and fullness.
Clinical evidence: In SURMOUNT trials, Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks alongside a reduced-calorie diet and increased activity. Wegovy (in STEP trials) showed average weight loss of approximately 15% of body weight. Saxenda typically results in 5–clinically studied weight loss. These figures represent trial averages—individual results vary significantly, and weight loss is not assured.
All three medications work best when combined with lifestyle changes, not as replacements for them. They require a prescription following clinical assessment and are subject to UK medical eligibility criteria based on BMI and health conditions.
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 Vs Private Access: How To Find Out If You're Eligible
In the UK, weight management treatment is delivered through a tiered NHS system. You can access prescription weight loss medication through NHS specialist (tier 3) weight management services by referral from your GP, though waiting lists vary significantly by region and can be lengthy. Alternatively, private prescribing is available through GPhC-registered online pharmacies following an online clinical assessment—no NHS referral needed.
General eligibility criteria include a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can discuss which option suits your circumstances and help you understand whether you meet eligibility criteria for prescription weight loss medication.
Check your BMI first using our free BMI calculator on this page to understand where you sit on the NHS weight management scale. Calculate your weight management potential with our GLP-1 weight loss calculator, which can help estimate projected outcomes at different medication doses. These tools are informational only—they don't replace clinical assessment, which is required before any prescription is issued.
- 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 weight loss injections assures specific weight loss results like "before and after" pictures show?
No. Weight loss injections may support weight management, but individual results vary significantly based on dose, adherence, diet, physical activity, and personal metabolism. Clinical trials show averages (15–21% for Mounjaro, ~15% for Wegovy), but some people lose less, some lose more. Before/after images online often don't represent typical results. Your GP or prescriber can discuss realistic expectations for your situation.
What's the difference between "before and after" results claimed privately versus NHS outcomes?
Results depend on the individual, not the prescriber source. Both private and NHS prescribing use the same medications. Private providers often market with individual success stories, while NHS data focuses on population averages. Individual outcomes vary regardless of whether you access treatment privately or through the NHS.
How long does it take to see weight loss results from injections?
Most people begin noticing appetite reduction within 1–2 weeks of starting, but meaningful weight loss typically becomes visible after 4–8 weeks. Maximum results are usually seen after 12–16 weeks at a stable dose. Weight loss is gradual and sustainable—rapid changes are not typical or recommended.
Are weight loss injections suitable for everyone wanting to lose weight?
No. Prescription weight loss medications are for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. They are not suitable for people under 18, pregnant or breastfeeding individuals, or those with certain medical contraindications. Your GP or a licensed prescriber will assess whether medication is appropriate for you.
How much does a weight loss injection cost in the UK, and what's included?
NHS access is free but involves waiting times and regional variation. Private costs typically range from £129–£320 per month depending on dose and provider. Costs cover the medication only—prescriber consultations vary. Both NHS and private routes require ongoing monitoring and follow-up appointments.
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.