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
Diet Plan For Weight Loss UK — Medication & Support Options
A successful diet plan for weight loss in the UK combines dietary changes with tailored support. Whilst healthy eating and physical activity are the foundation of sustainable weight loss, many adults now have access to prescription weight management medications alongside lifestyle changes. The NHS supports a structured approach that includes behaviour change, exercise, and—for eligible individuals—prescription medication to improve outcomes. Understanding your options helps you make informed decisions with your GP about the best approach for your health.
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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 Prescription Weight Loss Options
For adults in the UK who are overweight or obese, three prescription medications are licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 and GIP/GLP-1 receptor agonist medications that work by reducing appetite, increasing satiety, and supporting better food choices when combined with a structured diet plan.
Eligibility: You may be eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights.
Clinical evidence from trials shows average weight loss of 15–21% body weight over 68–72 weeks when medication is combined with a calorie-controlled diet and increased physical activity. Individual results vary significantly. Our free GLP-1 weight loss calculator can help estimate 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 — How to Get Started
NHS route: You can ask your GP for a referral to your local tier 3 specialist weight management service. NHS access to prescription medications is typically through these services following assessment. Waiting times vary significantly by region—some areas have substantial delays.
Private route: GPhC-registered online prescribing services offer rapid access following an online clinical assessment with a UK-licensed prescriber. Costs typically range from £129–£320 per month depending on medication and dose.
Whichever route you choose, prescription weight loss medications work best alongside a reduced-calorie diet, increased physical activity, and behaviour change support. Your GP or prescriber will assess your individual eligibility and discuss which medication and approach is most appropriate for your circumstances and health profile.
- 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 best diet plan for weight loss in the UK?
The most effective UK weight loss diet plan combines a calorie deficit (typically 500 kcal/day for ~0.5kg weekly loss), regular physical activity, and behaviour change support. Evidence supports Mediterranean-style diets and intermittent fasting as sustainable approaches. The NHS recommends losing no more than 0.5–1kg per week. For eligible adults, adding prescription medication to your diet plan can significantly improve outcomes.
Am I eligible for prescription weight loss medication?
You may be eligible if you have a BMI of 30+ or BMI 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea). Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP or a licensed prescriber can assess your individual eligibility during a consultation.
How much weight can I lose with a diet plan and medication?
Clinical trials show average weight loss of 15–21% body weight over 68–72 weeks when combining prescription medication with a calorie-controlled diet and exercise. Individual results vary—some people lose more, others less. Weight loss depends on adherence to dietary changes, physical activity, medication dose, and individual metabolism.
How do I access weight loss medication in the UK?
Via NHS: ask your GP for a referral to specialist weight management services in your area. Via private: use GPhC-registered online prescribing services. Both require a clinical assessment to confirm eligibility. Our BMI calculator helps you understand your starting point and can support conversations with your GP about which approach suits you.
Should I diet or use weight loss medication?
These work best together, not instead of each other. A reduced-calorie diet and physical activity are essential regardless of whether you use medication. For eligible adults, prescription medication significantly increases weight loss when combined with lifestyle changes—but without the diet and exercise component, medication alone is less effective.
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.