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 Weekly Diet: UK Medication & NHS Guide
A structured weekly diet plan is a practical starting point for weight management in the UK, but prescription medication may offer additional support for eligible adults. Whether you're managing through dietary changes alone or exploring prescription options like GLP-1 injections, understanding your choices helps you make informed decisions about your health. This guide covers NHS-approved weight loss medication available in the UK, who qualifies, and how to access support through your GP or private prescribers. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes with medication support.
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 Prescription Weight Loss Options
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks when combined with reduced-calorie diet and physical activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist given once weekly. Clinical evidence demonstrates average weight loss of approximately 15% body weight at the maximum dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist administered daily. Effective for weight management though requires once-daily injections rather than weekly.
Eligibility typically requires a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. Individual results vary significantly, and all prescription weight loss medications work best alongside dietary changes and increased physical activity — they are not replacements for lifestyle modifications.
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 Access vs Private Prescribing in the UK
NHS route: Weight loss medication through the NHS is accessed via specialist tier 3 weight management services. Your GP can refer you if you meet eligibility criteria, though waiting lists vary significantly by region and may extend several months. NICE has approved tirzepatide (Mounjaro) for NHS use, but regional availability differs.
Private route: UK-licensed online prescribers offer faster access without NHS referral. You'll complete an online clinical assessment, and if approved by a UK-licensed doctor, receive a prescription dispensed by a GPhC-registered pharmacy. This typically costs £129–£320 monthly depending on dose.
Either pathway requires a clinical assessment confirming suitability. Start by discussing your weight management goals with your GP — they can advise whether prescription medication is appropriate for you and explain local NHS options.
- 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 get weight loss medication on the NHS?
Yes, if you meet eligibility criteria. You'll need referral to a specialist weight management service (tier 3) by your GP. NICE has approved tirzepatide (Mounjaro) for NHS use, though availability and waiting times vary by region. Contact your GP surgery to ask about local pathways and current waiting lists in your area.
What's the difference between a weekly diet plan and prescription medication?
A structured weekly diet creates a calorie deficit through food choices alone. Prescription GLP-1 medications complement dietary efforts by reducing appetite and helping you feel fuller on smaller portions. Both work together — medication is most effective when combined with dietary changes and physical activity, not as a replacement for them.
How much weight can I expect to lose with prescription weight loss medication?
Clinical trials show average weight loss of 15–21% body weight over 72 weeks with Mounjaro, and approximately 15% with Wegovy, when combined with reduced-calorie diet and exercise. However, individual results vary significantly — some people lose more, some less. Your GP or prescriber can discuss realistic expectations based on your circumstances.
Am I eligible for weight loss medication if my BMI is between 25 and 30?
Generally, prescription weight loss medication is offered to adults with BMI 30 or above, or BMI 27–29.9 if you have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply. Check with your GP about your individual eligibility.
How do I start exploring weight loss medication options?
Begin by discussing your weight management goals with your GP. They can assess whether medication is suitable, explain NHS pathways in your area, or discuss private prescribing options. Use our BMI calculator and GLP-1 weight loss calculator on this page to understand your starting point and explore potential outcomes before your GP conversation.
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.