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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Top Rated Weight Loss Programs in the UK
Finding an effective weight loss program depends on your individual health needs, BMI, and access to specialist services. In the UK, top-rated weight management approaches range from NHS-supported lifestyle programmes to prescription weight loss medication for eligible adults. This guide explains the prescription medication options available, who qualifies, and how to access them through both NHS and private routes. Whether you're managing your weight for health reasons or working towards a healthier BMI, understanding your options is the first step.
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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 Medications
Three prescription-only medications are currently licensed in the UK for weight management in adults who meet eligibility criteria. These are evidence-based options recommended alongside reduced-calorie diet and increased physical activity.
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, administered as a once-weekly injection. Clinical trials showed participants lost an average of 15–21% of their body weight. Maximum dose is 15mg weekly.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, given once weekly by injection. Clinical data demonstrated average weight loss of approximately 15% body weight. Maximum dose is 2.4mg weekly.
- Saxenda (liraglutide) — A GLP-1 receptor agonist administered as a daily injection, with a maximum dose of 3mg daily.
All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly depending on adherence, lifestyle changes, and personal metabolism.
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 and How to Get Started
NHS route: Referral to a tier 3 specialist weight management service through your GP. Access varies significantly by region, and waiting lists can be lengthy in some areas. Private route: Online consultation with a UK-licensed prescriber, followed by prescription dispensing through a GPhC-registered pharmacy — no NHS referral needed.
To find out if you're eligible, check your BMI using our free BMI calculator on this page. Generally, adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (such as type 2 diabetes, high blood pressure, or heart disease), may qualify. Start by speaking with your GP about weight loss medication options and specialist referral, or explore private prescribing services that offer online assessments.
- 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 BMI do I need to qualify for prescription weight loss medication in the UK?
Adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions, typically qualify. Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage (from BMI 27.5+). Use our free BMI calculator to check your current BMI.
How much weight can I realistically lose with prescription weight loss injections?
Clinical trials show average weight loss of 15–21% of body weight, though individual results vary significantly. This is achieved alongside a reduced-calorie diet and increased physical activity. Your GP or prescriber can discuss realistic expectations based on your personal circumstances.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with higher average weight loss (15–21%) in trials. Wegovy (semaglutide) is a GLP-1 agonist only with average weight loss around 15%. Both are once-weekly injections. Your prescriber will assess which is most suitable for you.
Can I get weight loss medication through the NHS?
Yes, through NHS specialist tier 3 weight management services. Refer to your GP for referral. However, waiting times vary by region and can be lengthy. Private prescribing services offer faster access if you meet eligibility criteria.
Are there side effects with prescription weight loss medication?
Common side effects include nausea, diarrhoea, vomiting, and constipation — typically mild and temporary. Serious side effects are rare but can include pancreatitis or gallbladder issues. Your prescriber will discuss all risks and benefits during your clinical assessment.
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.