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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Quick Weight Loss in the UK — Prescription Medication Options
If you're looking for quick weight loss in the UK, prescription medications may be an option worth exploring with your GP. While sustainable weight management typically takes time, licensed weight loss injections can support faster results when combined with lifestyle changes. This guide explains the prescription weight management options available in the UK, who is eligible, and how to access them through the NHS or privately.
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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.
UK-Licensed Weight Loss Medications
Three prescription-only medicines are currently licensed in the UK for weight management in adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection. Clinical trials show these medications help with weight management: Mounjaro users lost an average of 15–21% of body weight, while Wegovy users lost approximately 15% on average—though individual results vary significantly. These medications work by activating GLP-1 (and GIP, in Mounjaro's case) hormone pathways, which help reduce appetite and support feeling fuller after meals. All three are prescription-only and require a clinical assessment before being prescribed. Eligibility typically includes adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Use our free GLP-1 weight loss calculator above to estimate potential results at different doses, and our BMI calculator to check your current BMI and understand your eligibility.
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 in the UK
NHS access to prescription weight loss medication is through specialist tier 3 or tier 4 weight management services. You'll typically need a GP referral, and availability varies significantly by region—many areas have lengthy waiting lists. Private access is faster: you can arrange a consultation with a UK-licensed prescriber through a GPhC-registered online service, receive a prescription if clinically appropriate, and have medication dispensed by a regulated pharmacy. Private costs typically range from £129–£320 per month depending on dose. Either route requires a clinical assessment confirming you meet eligibility criteria. Your GP can advise whether prescription medication is suitable for you, discuss your options, and help you understand the best route—NHS or private—based on your circumstances. Track your weight loss progress using our free progress tracker once you start treatment.
- 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 fastest way to lose weight in the UK with medication?
Prescription GLP-1 medications like Mounjaro and Wegovy can support faster weight loss than diet alone, with clinical trials showing 15–clinically studied weight loss. However, results vary by individual, and all medications work best alongside reduced-calorie diet and physical activity. Your GP or prescriber can assess the fastest safe option for you.
Am I eligible for NHS weight loss medication?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease). Contact your GP for a referral to specialist weight management services, though waiting times vary by region.
How quickly will I see results with weight loss injections?
Weight loss usually becomes noticeable after 4–8 weeks on prescription medication, with most significant results seen after 16–20 weeks. The NHS recommends gradual loss of 0.5–1 kg per week for sustainable results, even with medication.
Can I get weight loss medication privately in the UK?
Yes. You can arrange a private online consultation with a UK-licensed prescriber, and if approved, have medication dispensed by a GPhC-registered pharmacy. This route is faster than NHS but costs between £129–£320 monthly depending on the medication and dose.
Do weight loss injections work without diet and exercise?
Prescription weight loss medications are designed to work *alongside* lifestyle changes, not instead of them. Clinical trials show best results when medication is combined with a reduced-calorie diet and increased physical activity.
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.