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
6 Week Weight Loss: UK Prescription Medication Options
Achieving meaningful weight loss in six weeks is possible with the right support. For eligible UK adults, prescription weight management medications can be a helpful tool alongside diet and exercise. This guide covers the prescription weight loss medications licensed in the UK, who qualifies, and how to access them through NHS weight loss services or private prescribing. Individual results vary, but clinical evidence shows these medicines can support significant weight reduction when used as part of a structured approach.
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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 Available Now
Three prescription-only medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection. In clinical trials, Mounjaro showed average weight loss of 15–21% of body weight, and Wegovy showed approximately 15% loss—though individual results vary significantly. These are GLP-1 receptor agonists (with Mounjaro being a dual GIP/GLP-1 agonist) that work by reducing appetite, helping you feel fuller, and supporting better food choices. To determine if prescription weight loss medication is right for you, use our free BMI calculator above to check your starting point and eligibility criteria.
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: Getting Started in Six Weeks
In the UK, prescription weight loss medication is available through two routes. NHS access requires referral to a specialist tier 3 weight management service, though availability and waiting times vary by region—some areas have waiting lists exceeding six months. Private access is faster: you can access prescription weight loss treatment within days through online consultations with UK-licensed prescribers. Both routes require a clinical assessment to confirm eligibility based on BMI and health conditions. Your GP can discuss which route suits you, or you can pursue private prescribing independently. To understand your personal BMI category and weight loss potential, try our GLP-1 weight loss calculator to see projected outcomes at different doses.
- 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 lose significant weight in 6 weeks with prescription medication?
Clinical evidence shows weight loss becomes noticeable within 2–4 weeks for many users, with average losses of 15–21% over longer periods. However, results vary. Most prescribers recommend these medications as part of a 12–16 week minimum programme. Six weeks may show modest initial loss alongside lifestyle changes—enough to motivate further progress.
Who is eligible for prescription weight loss medication on the NHS in the UK?
NHS eligibility typically requires a BMI of 30 or above, or 27+ with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply (BMI 27.5+). Your GP can assess your eligibility.
How long does it take to get prescription weight loss medication privately in the UK?
Private prescribing is much faster than NHS. Many providers can complete an online assessment and issue a prescription within 24–48 hours. You can often receive your first dose within 3–5 days, meaning treatment can start within a week—well within a six-week timeframe.
Will prescription weight loss medication work without diet and exercise changes?
No. Clinical trials show weight loss medication works best alongside a reduced-calorie diet and increased physical activity. The medication supports appetite control and makes it easier to stick to healthier habits, but lifestyle changes are essential for meaningful, sustained results.
What's the difference between Mounjaro, Wegovy, and Saxenda for quick weight loss?
Mounjaro (tirzepatide) is a newer dual-action medication showing slightly higher average weight loss than Wegovy. Wegovy is an established once-weekly GLP-1 injection. Saxenda is a daily injection. All are prescription-only. Your prescriber will recommend the most suitable option based on your health, preferences, and eligibility.
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.