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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Weight Loss Programme and Gym — Adding Medication Support in the UK
A structured weight loss programme combined with regular gym activity is proven to deliver sustainable results, and for eligible adults in the UK, prescription weight management medication can provide additional support. Whether you're starting a fitness routine or looking to enhance your current programme, understanding your options—including NHS and private pathways—helps you make informed decisions about your health journey.
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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 Prescription Weight Loss Options
Three prescription weight management medications are currently licensed in the UK for eligible adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection.
In clinical trials, these medications helped participants achieve meaningful weight loss alongside reduced-calorie diets and increased physical activity. Mounjaro showed average weight loss of 15–21% of body weight, whilst Wegovy demonstrated approximately 15% average loss. Results vary significantly between individuals.
Eligibility criteria: Adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea) may be eligible. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds apply.
All three medications are prescription-only and require clinical assessment before prescribing. They work best when combined with your gym programme and reduced-calorie diet—medication supports your efforts but does not replace lifestyle changes.
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 in the UK
NHS route: Prescription weight loss medication is available through NHS specialist tier 3 weight management services. You'll need a referral from your GP to access this pathway. Availability and waiting times vary significantly by region, and in many areas, NHS services are oversubscribed.
Private route: You can access prescription weight loss medication privately through GPhC-registered online prescribing services without an NHS referral. After an online clinical assessment with a UK-licensed prescriber, medication is dispensed by a registered pharmacy. This typically offers faster access but involves costs (usually £129–£320+ per month depending on dose).
To find out if you're eligible, start by discussing weight management with your GP—they can advise on NHS services in your area or recommend private options. Use our free BMI calculator to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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.
Can I take weight loss medication while going to the gym?
Yes. Prescription weight loss medications are designed to work alongside increased physical activity and reduced-calorie diet. Gym workouts, combined with medication and dietary changes, support sustainable results. Always inform your prescriber about your fitness routine and any changes to your exercise level.
How quickly will I see results from a weight loss programme with medication?
Weight loss typically begins within the first few weeks, though individual timelines vary. Most people experience gradual, sustainable loss of 0.5–1 kg per week alongside their gym programme. Clinical trials showed meaningful results by 12–16 weeks. Results depend on adherence to your diet, exercise, and medication regimen.
Do I need a referral from my GP to access prescription weight loss treatment?
For NHS access, yes—you'll need a GP referral to a specialist weight management service. For private prescription weight loss medication, you don't need a referral; you can access services directly through online prescribers after a clinical assessment. Either way, discussing your goals with your GP is a good first step.
What is the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. In trials, Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%), though individual results vary. Your prescriber will advise which is more suitable for you.
How much does prescription weight loss medication cost privately in the UK?
Private prescription weight loss medication typically costs between £129 and £320+ per month, depending on the medication, dose, and provider. Initial consultations usually cost £40–£100. NHS access is free if you're eligible and referred through your GP, but waiting times vary by region. Check with private providers for current pricing.
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.