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 Methods — UK Prescription Options
If you're exploring weight loss methods in the UK, prescription medication is now an evidence-based option for eligible adults. GLP-1 receptor agonist injections like Mounjaro and Wegovy, alongside lifestyle changes, can support significant weight management. This guide covers UK-licensed weight loss medications, eligibility criteria, how to access them through the NHS or privately, and how to have an informed conversation with your GP about whether prescription weight loss is suitable for you.
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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.
UK-Licensed Prescription 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, once-weekly injection. In clinical trials, participants on the maximum 15mg dose lost an average of 20.9% of their body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, once-weekly injection. Clinical trial data showed an average weight loss of approximately 14.9% of body weight at 68 weeks on the maximum 2.4mg dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, but administered as a daily injection rather than weekly.
All three are prescription-only medicines requiring clinical assessment before being prescribed. Individual results vary significantly, and these medications work most effectively when combined with dietary changes and physical activity. Use our free 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 Access vs Private Prescribing
NHS route: Prescription weight loss medications are available through specialist tier 3 weight management services, accessed via GP referral. However, availability varies significantly by region, and waiting lists can be lengthy in many areas.
Private route: You can access prescription weight loss medication through a private online consultation with a UK-licensed prescriber, dispensed by a GPhC-registered pharmacy. This does not require NHS referral and is often faster, though at personal cost.
Either way, a qualified prescriber will assess your BMI, health history, and weight-related conditions. Calculate your current BMI using our free calculator above to help you understand whether you may be eligible.
- 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.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 kg/m² or above are generally eligible. Those with a BMI of 27–29.9 kg/m² may be eligible if they have weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. People of South Asian, Chinese, Black African, or Black Caribbean heritage have lower BMI thresholds. A prescriber will assess your individual circumstances.
How much weight will I lose on prescription weight loss medication?
Clinical trials show average weight loss ranging from approximately 15% to 21% of body weight depending on the medication and dose. However, individual results vary considerably. Weight loss is most effective alongside a reduced-calorie diet and increased physical activity. These medications are tools to support lifestyle change, not substitutes for it.
How do I know if I should talk to my GP about weight loss medication?
If you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions, consider asking your GP whether weight loss medication might be appropriate for you. Your GP can discuss options, explain eligibility based on NHS guidance in your region, and refer you to specialist services if suitable.
Are prescription weight loss injections available on the NHS?
Yes, NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use within specialist weight management services. However, access is through tier 3 specialist services following GP referral, and regional availability varies. Private prescribing offers faster access without NHS referral, at personal cost.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials suggest Mounjaro may produce slightly greater average weight loss, though both are effective. Mounjaro is once weekly; Wegovy is also once weekly. Individual response varies, and prescriber assessment determines which is most suitable.
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.