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
Setting Realistic Weight Loss Goals in the UK
Setting achievable weight loss goals is the foundation of sustainable health improvement. In the UK, adults looking to lose weight have several evidence-based options available, including prescription medications for eligible individuals. Whether you're aiming for a modest 5% reduction or a more significant change, understanding what's realistic, how medications can help, and what support is available through the NHS or private providers will help you create a plan that works for you. Use our free BMI calculator to establish where you're starting from, and our weight loss projection calculator to explore potential outcomes with medical support.
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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 weight management medications are currently licensed in the UK for eligible adults:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, dosed from 2.5 mg to 15 mg weekly. Clinical trials showed an average weight loss of 15–21% of body weight alongside diet and exercise.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, dosed up to 2.4 mg weekly. Clinical evidence demonstrates approximately 15% average body weight loss in trials.
- Saxenda (liraglutide) — A daily GLP-1 injection, dosed up to 3 mg per day.
All three work by helping regulate appetite and supporting feeling fuller after meals. Individual results vary significantly, and these medications are always used alongside reduced-calorie diet and increased physical activity — not as a replacement for lifestyle change.
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 Routes
In the UK, prescription weight loss medication is accessed through two pathways. NHS access is through specialist tier 3 or tier 4 weight management services — your GP can refer you if you meet the criteria, though waiting lists vary widely by region and can be lengthy. Private access is available through UK-licensed online prescribers following a clinical assessment, with no NHS referral required.
To find out if you're eligible, speak to your GP or consult a private prescriber. Eligibility typically includes 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 sleep apnoea. Use our free weight converter and BMI tool to check your current measurements and discuss the results with your healthcare provider.
- 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 a realistic weight loss goal?
The NHS recommends losing 0.5–1 kg per week for sustainable results. A 5–10% reduction in body weight can produce meaningful health benefits, including improved blood pressure and blood sugar control. Faster loss is possible with medical support but requires professional oversight. Your GP can help set a personalised goal based on your health.
Am I eligible for prescription weight loss medication in the UK?
Generally, you may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition such as diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds. A prescriber will assess your individual circumstances.
How quickly do GLP-1 medications like Mounjaro and Wegovy work?
Weight loss typically becomes noticeable within 4–8 weeks as doses are gradually increased. Most significant losses occur between weeks 8 and 24. However, everyone responds differently. Some people see steady, gradual losses; others see more rapid early changes. Patience and consistency are important.
Can I use weight loss medication without changing my diet or exercise?
No. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. These are not standalone treatments. Your prescriber will discuss lifestyle expectations before starting. Medication supports your efforts—it doesn't replace them.
What's the difference between NHS and private weight loss medication?
NHS access is free but involves referral to specialist services and can have long waiting lists. Private access is faster and doesn't require NHS referral but involves a cost (typically £150–£300+ per month depending on medication and dose). Both require a prescription from a UK-licensed prescriber and a 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.