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
Fat Stomach Weight Loss — Prescription Options in the UK
Losing weight around the stomach area can be challenging, especially when diet and exercise alone haven't worked. In the UK, prescription weight management medications are available for eligible adults. These prescription options include GLP-1 receptor agonist injections like Wegovy and dual GIP/GLP-1 medications like Mounjaro, which may help reduce appetite and support weight loss when combined with lifestyle changes. This guide explains what's available through the NHS and privately, who can access these treatments, and how to find out if you're eligible.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Medications
Three prescription medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide), a GLP-1 receptor agonist; and Saxenda (liraglutide), another GLP-1 option. All are injection-based and require a prescription following clinical assessment.
Clinical evidence: In trials, Mounjaro helped participants lose an average of 15–21% of their body weight, whilst Wegovy achieved approximately 15% average weight loss. Individual results vary significantly and depend on dose, adherence, and lifestyle changes. These medications work by signalling fullness to the brain, reducing appetite, and slowing digestion—potentially helping with cravings and portion control, particularly beneficial for abdominal weight loss.
Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different doses.
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 medications are available through specialist tier 3 weight management services. You'll need a GP referral and assessment by a specialist team. Availability varies significantly by region, and waiting times can be lengthy—often months to over a year in some areas. However, if approved, treatment costs are covered by the NHS.
Private route: You can access these medications privately through online consultations with UK-licensed prescribers without waiting for NHS referral. A clinical assessment is still required to ensure the medication is appropriate for you. Private prescriptions are dispensed by GPhC-registered pharmacies, with costs typically ranging from £129–£320 per month depending on dose.
Whichever route you choose, prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Track your progress using our free progress tracker to monitor weight loss over time.
- 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 get weight loss medication on the NHS for a fat stomach?
Yes, if you meet eligibility criteria. You'll need a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Ask your GP for a referral to a specialist weight management service. However, NHS availability varies by region and waiting times can be significant. Your GP can advise on local options and waiting lists.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription injections taken weekly. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is a single GLP-1 agonist. Mounjaro may offer slightly higher average weight loss (15–21% vs 15%), but individual results vary. Your prescriber will assess which is more suitable based on your health history and preferences.
How quickly will I lose weight with prescription medication?
The NHS recommends safe weight loss of 0.5–1 kg per week. With prescription medications, loss may be faster initially, but this varies greatly between individuals. Results depend on dose, adherence, diet, and exercise. Expect to see changes over weeks to months, not days. Track progress with realistic timelines in mind.
Do I need to change my diet if I take weight loss medication?
Yes. Prescription weight loss medications are most effective when combined with a reduced-calorie diet and increased physical activity. The medication helps reduce appetite and cravings, making dietary changes easier, but it's not a standalone treatment. Lifestyle changes are essential for sustainable results.
What happens when I stop taking prescription weight loss medication?
Weight may return if diet and exercise habits don't remain consistent. These medications are tools to support weight management, not permanent solutions. Long-term success depends on maintaining healthy eating and activity levels. Discuss long-term management plans with your prescriber or GP.
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.