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 in Gym: UK Prescription Options
A structured weight loss programme in the gym works best when combined with the right support — and for many UK adults, that includes prescription weight management medication. If you're struggling with excess weight despite regular exercise, prescription options like Mounjaro and Wegovy may be available to you through the NHS or private prescription. This guide explains what's available in the UK, who is eligible, and how to start the conversation with your GP about prescription weight loss support alongside your gym routine.
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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 medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, whilst Saxenda is a daily injection. All work by helping reduce appetite and food cravings, allowing you to stick more closely to your gym-based weight loss programme without constant hunger.
In clinical trials, adults using these medications alongside a reduced-calorie diet and increased physical activity — like your gym programme — lost significantly more weight than diet and exercise alone. Mounjaro users lost an average of 15–21% of their body weight, whilst Wegovy users lost approximately 15% over 68 weeks. These are prescription-only medicines requiring clinical assessment before being prescribed.
Eligibility typically requires a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like high blood pressure, type 2 diabetes, or heart disease. Use our free BMI calculator above to check your starting BMI and understand what category you fall into.
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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.
Getting Prescription Weight Loss Support: NHS vs Private
In the UK, prescription weight loss medication is available through two routes. The NHS route involves referral to a specialist tier 3 weight management service through your GP — these services assess your eligibility and prescribe medication as part of a structured programme. However, NHS availability varies significantly by region and waiting lists can be lengthy in many areas.
The private route offers faster access through UK-licensed online prescribers and pharmacies. After a clinical assessment, a prescriber determines if medication is suitable for you. Start by speaking with your GP about whether prescription weight loss medication could support your gym-based programme. They can refer you to NHS services or advise on private options. Either way, medication works best alongside your existing exercise routine — not as a replacement for it.
- 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 use weight loss medication alongside my gym routine?
Yes. Prescription weight loss medications like Mounjaro and Wegovy are specifically designed to be used alongside reduced-calorie diet and increased physical activity — including gym-based exercise programmes. In fact, clinical trials combined medication with both dietary changes and exercise, so your gym routine is an important part of the overall approach to achieving results.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Clinical trial data shows Mounjaro may produce slightly higher average weight loss (15–21% versus ~15%), but individual results vary. Your prescriber will assess which is more suitable for you based on your health profile.
How quickly will I see weight loss results?
Weight loss is typically gradual and varies between individuals. The NHS recommends losing 0.5–1 kg per week as a sustainable rate. With prescription medication alongside your gym programme and dietary changes, most people begin noticing changes within the first few weeks, though significant results usually appear over months. Our free progress tracker can help you log your journey.
Will prescription weight loss medication work without gym exercise?
Medication is most effective when combined with exercise and dietary changes. Clinical trials specifically tested medication alongside reduced-calorie diet and increased physical activity. Your gym routine strengthens this effect — the combination of medication, diet, exercise, and support produces the best outcomes. Medication alone is not a substitute for lifestyle changes.
How do I find out if I'm eligible for prescription weight loss medication on the NHS?
Start by speaking with your GP. You're typically eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Your GP can assess your individual circumstances and refer you to a specialist weight management service if appropriate. They can also advise whether private prescription options might suit you better based on waiting times in your area.
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.