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
What Is a Medical Weight Loss Program?
A medical weight loss program is a structured, healthcare-led approach to managing weight through prescription medications, clinical support, and lifestyle changes. In the UK, medical weight loss programs are available through both NHS specialist services and private prescribing routes. Unlike self-help dieting, these programs involve assessment by a qualified healthcare professional to determine eligibility and monitor progress. They may include prescription medications like GLP-1 injections alongside dietary guidance and activity support. Medical weight management can be particularly effective for people with a BMI over 30, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes or high blood pressure.
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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.
How Medical Weight Loss Programs Work in the UK
A medical weight loss program typically involves several key stages:
- Initial assessment: A GP or specialist healthcare professional evaluates your health, medical history, weight, and any existing conditions to determine suitability for prescription weight management.
- Eligibility check: You'll be assessed against NHS or private prescribing criteria — usually BMI ≥30, or BMI 27–29.9 with weight-related health conditions.
- Prescription medication (if appropriate): If suitable, you may be prescribed a GLP-1 medication such as Wegovy (semaglutide). These weight loss injections work by reducing appetite and helping you feel fuller after smaller meals.
- Monitoring and support: Regular check-ins track your progress, manage any side effects, and adjust your dose if needed.
- Lifestyle integration: Prescription weight loss medication works best alongside a reduced-calorie diet and increased physical activity — medication alone is not sufficient.
Try our GLP-1 weight loss calculator to estimate potential outcomes at different doses, or use our BMI calculator to check your current eligibility status.
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 Medical Weight Loss Programs
NHS route: Access through tier 3 specialist weight management services via GP referral. Typically free at point of use but availability varies significantly by region, and waiting lists can be lengthy (sometimes months or years). Referral criteria usually require BMI ≥35, or BMI ≥30 with weight-related health conditions.
Private route: Available through GPhC-registered pharmacies offering private prescribing services. Requires an online clinical assessment with a UK-licensed prescriber. Faster access (often within days) but costs range from approximately £129–£320 per month depending on medication dose. Private prescribing does not require NHS referral.
Both routes offer prescription weight loss medication and clinical monitoring. Your choice depends on availability, waiting times, and cost. Track your weight loss progress with our free progress tracker once you've started treatment.
- 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.
Is a medical weight loss program the same as a diet?
No. A diet is self-directed eating changes, often without professional support. A medical weight loss program involves assessment by a healthcare professional, prescription medication (if appropriate), clinical monitoring, and structured guidance. Medical programs address underlying health factors and use evidence-based medication alongside lifestyle support.
What is the most common prescription for medical weight loss in the UK?
Wegovy (semaglutide) and Mounjaro (tirzepatide) are the most commonly prescribed GLP-1 medications for weight management. Both are once-weekly injections. In clinical trials, Wegovy resulted in average weight loss of approximately 15% of body weight, and Mounjaro approximately 15–21% — though individual results vary significantly. Both require prescription-only status and clinical assessment.
How much weight can I expect to lose on a medical weight loss program?
Results vary widely between individuals. Clinical evidence suggests GLP-1 medications support average weight loss of 15–20% of body weight over 12–18 months when combined with diet and activity changes. However, some people lose more, others less. Your prescriber can give you a more personalised estimate based on your health and circumstances.
Can I access medical weight loss medication through the NHS?
Yes, but availability varies. You need referral to a tier 3 specialist weight management service through your GP. NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use, but prescribing depends on regional funding and service availability. Many areas have long waiting lists. Private prescribing offers faster access if you prefer.
What's the difference between Ozempic and Wegovy?
Both contain semaglutide but serve different purposes. Ozempic is licensed for type 2 diabetes management at doses up to 2mg — using it for weight loss is off-label. Wegovy is specifically licensed for weight management in the UK at doses up to 2.4mg. Always use the medication licensed for your intended purpose and prescribed by your healthcare professional.
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.