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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Best Weight Loss Plan UK: Prescription & Lifestyle Options
Finding the right weight loss plan depends on your individual circumstances, BMI, and health needs. In the UK, you have access to evidence-based approaches ranging from lifestyle changes and NHS-supported programmes to prescription weight management medication. This guide covers the main options available to UK adults, how to check your eligibility, and how to start a conversation with your GP about the best 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 Weight Loss Medication Options
If you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with weight-related health conditions, you may be eligible for prescription weight loss medication in the UK. Three medications are currently licensed for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly, clinical trials showed average weight loss of 15–21% body weight
- Wegovy (semaglutide) — a GLP-1 receptor agonist given once weekly, with evidence of approximately 15% average body weight loss
- Saxenda (liraglutide) — a once-daily GLP-1 injection, the longest-established weight loss medication in the UK
All prescription options work best alongside a reduced-calorie diet and increased physical activity. Our free GLP-1 weight loss calculator can help you explore potential outcomes at different doses. Individual results vary significantly depending on adherence, lifestyle factors, and your personal response to the medication.
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 the UK, prescription weight loss treatment is available through two routes: NHS specialist weight management services (tier 3/4) or private prescribing following an online clinical assessment with a UK-licensed prescriber.
NHS access typically requires a GP referral to your local weight management service, though waiting times vary significantly by region. Private access is faster but involves costs starting from around £129–£320 per month depending on the medication and dose.
Start by speaking with your GP about your weight loss goals. They can assess your BMI using our free BMI calculator as a reference point, discuss your health history, and either refer you to NHS services or advise on private options. Be open about any weight-related health conditions you may have, as these can affect your eligibility and the best choice for you.
- 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 is the safest rate of weight loss?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week as a sustainable and safe rate. This typically requires a calorie deficit of around 500 kcal per day. Faster weight loss may result in greater muscle loss and is generally not recommended without medical supervision.
Can I use weight loss medication without changing my diet?
No. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Medications support appetite control and feelings of fullness, but sustainable weight loss requires lifestyle changes. Your prescriber will discuss this during your clinical assessment.
How long do I need to take weight loss medication?
This varies by individual. Some people take medication for several months to reach their goal, while others continue longer-term for weight maintenance. Your prescriber will review your progress regularly and discuss the best duration for you. Stopping medication may result in weight regain without ongoing lifestyle changes.
Am I eligible for weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, etc.). NHS eligibility and availability vary by region. Your GP can assess whether you meet your local criteria and refer you to specialist services.
What should I discuss with my GP about weight loss plans?
Discuss your weight loss goals, any weight-related health conditions, previous attempts at weight loss, your lifestyle (diet, exercise, stress), and whether medication might help. Bring your BMI or use our free BMI calculator beforehand. Your GP can then advise on NHS services, private options, or structured lifestyle programmes 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.