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 Drug Options in the UK
If you're looking for losing weight drug options in the UK, you have several paths available — from lifestyle support programmes to prescription medications and specialist services. The right approach depends on your BMI, health conditions, and what you've already tried. This guide walks you through every option available to you, from free NHS weight management to prescription-only injections like Mounjaro and Wegovy. Your GP can help you find the best fit for your circumstances.
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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.
Weight Loss Methods Available in the UK
The UK health system offers a structured approach to sustainable weight loss across four tiers. Tier 1 includes free self-help tools, digital weight loss programmes, and community support — perfect for getting started without medical intervention. Tier 2 involves primary care support, where your GP can refer you to structured behaviour change programmes like the NHS Weight Loss Plan. Tier 3 is specialist weight management services, where multidisciplinary teams assess you and may prescribe medication. Tier 4 covers bariatric surgery for severe obesity with significant health complications. Our free BMI calculator above can help you understand which tier might be relevant to you. For sustainable weight loss, aim for 0.5 to 1 kg per week — faster loss risks losing muscle alongside fat. Most effective approaches combine dietary changes, increased physical activity, and behavioural support. Weight loss drugs are typically added to these lifestyle changes, not used instead of them.
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.
Prescription Weight Loss Medications
In the UK, three main prescription weight loss drugs are licensed: Mounjaro (tirzepatide), a once-weekly dual GIP and GLP-1 injection; Wegovy (semaglutide), a once-weekly GLP-1 injection; and Saxenda (liraglutide), a daily GLP-1 injection. All are prescription-only and require clinical assessment before prescribing. Try our GLP-1 weight loss calculator to see potential results at different doses. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. These medications work alongside reduced-calorie diet and physical activity — they're not standalone solutions. Access is through NHS specialist services (with potentially long waiting lists depending on your region) or private prescribing following an online consultation with a UK-licensed prescriber.
- 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's the difference between NHS and private weight loss drug options?
NHS weight loss drug prescriptions come through tier 3 specialist services, usually with waiting lists. Private access is faster — you can get a prescription within days through a UK-licensed prescriber following an online assessment. Both require clinical eligibility (BMI 30+ or 27+ with health conditions), but private services don't have regional availability restrictions.
Can I get weight loss drugs like Mounjaro on the NHS?
Yes — NICE has approved tirzepatide (Mounjaro) for NHS use in specialist weight management services. However, availability varies by region and waiting lists can be long. Your GP can refer you to your local tier 3 service, but access depends on your ICB's commissioning decisions.
How quickly will I lose weight on a weight loss drug?
Clinical trials show average weight loss of 15–21% of body weight over 68 weeks with prescription GLP-1 or GIP/GLP-1 medications. Individual results vary significantly. Weight loss is typically achieved alongside reduced-calorie diet and physical activity — the medication supports these lifestyle changes rather than causing weight loss alone.
Are weight loss drugs safe long-term?
Prescription weight loss drugs like Mounjaro and Wegovy have been tested in clinical trials lasting up to 68 weeks. Long-term safety data beyond 1–2 years is still emerging. Side effects are common but usually manageable. Always discuss risks and benefits with your prescriber before starting any medication.
What should I discuss with my GP about weight loss drug options?
Discuss your current weight, BMI, any weight-related health conditions, previous weight loss attempts, and lifestyle changes you're already making. Ask about NHS tier 3 services in your area, eligibility criteria, waiting times, and whether private prescribing might suit you better. Your GP can help identify which approach aligns with your health goals.
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.