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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1 Month Weight Loss Program in the UK
A structured one-month weight loss program in the UK can include prescription medication alongside lifestyle changes. If you're considering pharmaceutical support, three prescription options are currently licensed: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Each works differently and requires clinical assessment. This guide explains what's available through the NHS and private prescribing, who qualifies, and how to start a conversation with your GP about prescription weight management options.
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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.
UK-Licensed Prescription Weight Loss Medications
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a once-weekly injection that may help regulate appetite and support feeling fuller after meals. Clinical trials showed participants lost an average of 15–21% of their body weight alongside reduced-calorie diet and increased physical activity. Wegovy (semaglutide) is a GLP-1 injection, also once-weekly, with clinical evidence showing approximately 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection offering similar mechanisms but requires once-daily dosing. All three are prescription-only medicines requiring clinical assessment. Eligibility typically includes a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Individual results vary significantly — prescription medications work best when combined with dietary changes and increased physical activity, not as replacements for lifestyle modifications. Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
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 to Weight Loss Medication
NHS route: Available through tier 3 specialist weight management services following GP referral. Access varies significantly by region, and waiting lists can be lengthy (often several months to over a year). Your GP can refer you if you meet eligibility criteria. Private route: Available through GPhC-registered online prescribing services without NHS referral. A UK-licensed prescriber conducts an online clinical assessment, and medication is dispensed by a regulated pharmacy. Costs typically range from £129–£320 monthly depending on dose. Both routes require prescription — neither medication is available over-the-counter. Start by discussing weight management UK options with your GP, who can assess your individual health profile and advise whether prescription support is appropriate alongside your own bmi weight loss goals. Use our BMI calculator to understand your current health category before your conversation.
- 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 weight in one month using prescription medication?
Individual results vary significantly. Weight loss typically begins within weeks, but meaningful, sustainable progress develops over months. The NHS recommends losing 0.5–1 kg per week for safe, lasting results. Prescription medications are most effective when combined with reduced-calorie diet and exercise — they're not standalone solutions for gradual weight management in one month alone.
How do I find out if I'm eligible for NHS weight loss medication?
Start by speaking with your GP about your weight and health goals. You'll be assessed on BMI (typically 30+, or 27+ with weight-related conditions) and overall health profile. If eligible, your GP may refer you to a tier 3 specialist weight management service. NHS availability varies by region — your local integrated care board (ICB) determines what's offered in your area.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is GLP-1 only. Clinical trials suggest Mounjaro may offer slightly greater average weight loss (15–21% vs ~15%), but individual results vary. Both are once-weekly injections. Your prescriber will assess which is most appropriate based on your health profile and any other medications you take.
Is prescription weight loss medication covered by the NHS?
NHS coverage depends on your local ICB and tier 3 specialist service availability. Some regions offer tirzepatide (Mounjaro) and semaglutide (Wegovy), while others may only provide liraglutide (Saxenda) or none at all. Private prescribing is an alternative if NHS access is unavailable or waiting times are lengthy in your area. Costs and availability vary widely.
What should I discuss with my GP before starting a weight loss program?
Discuss your current weight, health conditions, medications, weight loss goals, and lifestyle capacity for dietary and exercise changes. Ask about NHS specialist referral options in your area, waiting times, and whether private prescribing might be suitable. Your GP can assess whether prescription medication is appropriate and help you understand realistic timelines for safe, sustainable weight loss alongside other health factors.
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.