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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Food Plan for Weight Loss — UK Medication Options
A food plan is the foundation of any weight management approach, but for eligible adults in the UK, prescription weight loss medication can significantly support your efforts. Combining a structured eating plan with approved treatments like Mounjaro or Wegovy may help you achieve better results than diet alone. This guide explains how prescription weight loss works in the UK, who is eligible, and how to start a conversation with your GP about the right approach for you.
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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
Three prescription medications are currently licensed in the UK for weight management alongside diet and exercise:
- Mounjaro (tirzepatide) — a once-weekly injection that activates both GIP and GLP-1 hormone pathways. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, though individual results vary.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. The STEP trial demonstrated average weight loss of approximately 15% alongside lifestyle changes.
- Saxenda (liraglutide) — a daily GLP-1 injection, available for weight management in the UK.
All three are prescription-only medicines requiring a clinical assessment. They work best when combined with a structured food plan and increased physical activity. The NHS recommends losing weight at a sustainable rate of 0.5–1 kg per week, which a food plan helps you achieve through calorie deficit while medication supports appetite control and cravings management.
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.
Eligibility and Access in the UK
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator to check your current BMI instantly.
NHS access: referral to a specialist tier 3 weight management service, though waiting lists vary significantly by region. Private access: through online consultation with a UK-licensed prescriber, available without NHS referral. Either route requires clinical assessment to confirm suitability. Start by speaking with your GP about whether prescription medication is appropriate for your weight management plan, or explore private options if NHS access is limited in your area.
- 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.
Should I follow a specific food plan with weight loss medication?
Yes. Prescription medications like Mounjaro and Wegovy work alongside diet and exercise — not instead of them. A structured food plan that creates a calorie deficit (typically 500 kcal/day for 0.5 kg weekly loss) helps you maintain consistent progress. Your GP or a registered dietitian can recommend an appropriate plan.
How quickly will I see results with a food plan and medication?
Individual results vary significantly. Clinical trials show weight loss begins within weeks for many people, with average losses of 15–21% over several months. However, sustainable weight loss combined with a food plan typically happens at 0.5–1 kg per week — this rate minimises muscle loss and supports long-term success.
Can I get prescription weight loss medication on the NHS?
Yes, but access is through specialist tier 3 weight management services after GP referral. Waiting lists vary by region — some areas have significant delays. Private options are available through online consultation with a licensed UK prescriber if NHS access is limited in your area.
What type of food plan works best with weight loss medication?
A balanced, reduced-calorie plan works best — whether Mediterranean, low-carb, or calorie-counting. The key is consistency and a deficit of around 500 kcal/day. Your GP, practice dietitian, or a registered nutritionist can tailor a plan to your preferences and health conditions.
How do I know if I'm eligible for prescription weight loss treatment?
Check your BMI using our free BMI calculator on this page. If your BMI is 30 or above, or 27–29.9 with weight-related health conditions, you may be eligible. Book an appointment with your GP to discuss your options and whether prescription medication is suitable for you.
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.