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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Medical Weight Loss Programs in the UK
Medical weight loss programs in the UK combine clinical assessment, prescription medication, and lifestyle support to help adults achieve sustainable weight management. These evidence-based programs are available through both NHS specialist services and private prescribing routes, tailored to your individual health needs. Whether you're looking to lose weight through UK weight management services or exploring GLP-1 weight loss options, understanding how these programs work is the first step toward achieving your health goals.
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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
Medical weight loss programs operate through a structured, tiered approach in the UK. The NHS four-tier model starts with tier 1 (self-help and digital tools), progresses through tier 2 (primary care behaviour change programmes), tier 3 (specialist multidisciplinary weight management services where prescription medication may be offered), and tier 4 (bariatric surgery for severe obesity). Private medical weight loss programs follow a similar assessment pathway but without NHS waiting lists. Both routes begin with a clinical assessment to establish your eligibility, medical history, and suitability for specific treatments. Prescription weight loss medication, such as GLP-1 receptor agonists (Wegovy, Mounjaro) or other approved medicines, is prescribed only after this assessment. Programs typically combine medication with dietary guidance, physical activity support, and progress monitoring to maximise sustainable results.
- NHS access through GP referral to tier 3 specialist services
- Private access via online consultation with UK-licensed prescriber
- Individual assessment determines eligibility and treatment suitability
- Medication combined with lifestyle changes for best outcomes
- Regular monitoring and dose adjustments as needed
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.
Eligibility and Treatment Options
You may be eligible for medical weight loss treatment if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, and Black Caribbean adults, lower thresholds apply due to higher cardiovascular risk at lower BMI levels. Licensed weight loss injections available in the UK include Wegovy (semaglutide), a GLP-1 injection taken once weekly, and Mounjaro (tirzepatide), a dual GIP/GLP-1 injection also given weekly. Both medications may help you feel fuller after smaller meals and reduce food cravings, with clinical trials showing average weight losses of 15–21% of body weight when combined with reduced-calorie diet and increased physical activity. Your prescriber will determine which treatment is most appropriate for your circumstances.
- 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 the difference between NHS and private medical weight loss programs?
NHS programs are accessed through GP referral to specialist tier 3 weight management services and are free, though waiting lists can be lengthy in many areas. Private medical weight loss programs offer faster access through online consultations with UK-licensed prescribers, available without NHS referral, but require payment. Both follow similar clinical assessment pathways and use evidence-based treatments.
How much weight can I expect to lose with a medical weight loss program?
Clinical trials show that prescription weight loss medications like Wegovy and Mounjaro may help achieve average weight losses of 15–21% of body weight over 68 weeks, alongside dietary changes and physical activity. However, individual results vary significantly — some people lose more, others less. Your prescriber will discuss realistic expectations for your situation.
Are prescription weight loss medications safe?
Prescription weight loss medications available in the UK are licensed and regularly monitored by the MHRA. Like all medications, they have side effects — nausea, diarrhoea, and constipation are common initially. Serious side effects are rare. Your prescriber will assess whether these medications are safe for you based on your medical history and will monitor you throughout treatment.
Do I need to change my diet and exercise 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. Medication alone is not sufficient for sustainable weight loss. Medical weight loss programs typically include guidance on both nutrition and exercise alongside medication.
How do I access a medical weight loss program in the UK?
For NHS access, speak with your GP about a referral to your local specialist weight management service (tier 3). For private access, you can consult with a UK-licensed prescriber online, who will assess your eligibility and issue a prescription if appropriate. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different treatment doses.
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.