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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Weight Loss in the UK — What Works and How to Get Support
Weight loss is a significant health goal for many UK adults, and there are now more evidence-based options available than ever before. Whether you're looking to manage your weight through lifestyle changes, prescription medication, or a combination of both, understanding what actually works—backed by NHS guidance and clinical evidence—is essential. This guide covers the most effective weight management strategies available to UK adults, including prescription weight loss injections, dietary approaches, and how to access professional support through both NHS and private channels.
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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
Lifestyle changes remain the foundation of sustainable weight management. The NHS recommends a calorie deficit of around 500 kcal per day, which typically results in losing approximately 0.5 to 1 kg per week. A balanced diet, regular physical activity, and behaviour change support are the first-line approaches for most adults.
For eligible adults, prescription weight loss medications are now available through both NHS specialist services and private prescribing. GLP-1 weight loss injections—including Wegovy (semaglutide) and Mounjaro (tirzepatide)—have shown significant results in clinical trials. Wegovy, licensed for weight management in the UK, helped participants in the STEP-1 trial lose an average of approximately 14.9% of their body weight alongside a reduced-calorie diet and increased physical activity.
Access through the NHS typically requires referral to a tier 3 specialist weight management service. Private access is available through GPhC-registered online pharmacies following a clinical assessment. Try our free GLP-1 weight loss calculator to explore potential weight loss outcomes at different doses, and use our BMI calculator to understand your current health category.
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.
Prescription Weight Loss Medication — Key Facts
Prescription weight loss injections in the UK are licensed for adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Wegovy (semaglutide) and Mounjaro (tirzepatide) are both once-weekly injections requiring a prescription and clinical assessment before use.
These medications are not quick fixes—they work best alongside reduced-calorie diet and increased physical activity. Individual results vary considerably, and side effects such as nausea and digestive changes are common, especially in the first few weeks. Your GP or a licensed prescriber can assess whether prescription weight loss treatment is appropriate for your individual circumstances. Track your progress with our free progress tracker to monitor weight changes over time.
- 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 Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is licensed for weight management (up to 2.4 mg) whilst Ozempic is approved for type 2 diabetes (up to 2 mg). Using Ozempic for weight loss is off-label. Wegovy is the licensed option for weight management in the UK.
How much weight can I expect to lose with prescription weight loss medication?
Clinical trials show average weight loss of 14–21% of body weight with GLP-1 medications alongside lifestyle changes. However, individual results vary significantly. Some people lose less, some lose more. Results depend on dose, adherence, diet, and exercise.
Can I get prescription weight loss treatment on the NHS?
Yes, but access is through specialist tier 3 weight management services, typically following GP referral. Availability varies by region and waiting lists can be long. Private access is also available through online prescribing services following a clinical assessment.
What side effects do weight loss injections cause?
Common side effects include nausea, diarrhoea, constipation, and stomach pain, particularly in the first few weeks. These often reduce over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder issues. Always discuss side effects with your prescriber.
Do I need to diet and exercise if I take weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They are not replacements for lifestyle changes—they are tools to support them. Your GP or prescriber can advise on dietary and exercise approaches.
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.