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 Meds: Your UK Guide to Prescription Options
Weight loss medications are prescription-only treatments available to eligible adults in the UK. Several GLP-1 and dual-action injections have been approved by the MHRA for weight management. These medications work alongside lifestyle changes—diet and physical activity remain essential. Access is available through both NHS specialist weight management services and private prescribing. This guide explains your options, eligibility criteria, and how to find out if prescription weight loss medication might be 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 Weight Loss Medications
Three prescription weight loss medications are currently licensed in the UK for adults with obesity or overweight with weight-related health conditions:
- Mounjaro (tirzepatide) — a once-weekly injection that activates both GIP and GLP-1 hormone pathways. Clinical trials showed average weight loss of approximately 15–21% of body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical trial data demonstrated average weight loss of around 14.9% of body weight at 68 weeks alongside reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a daily GLP-1 injection with a maximum dose of 3 mg. This is the older GLP-1 option, with evidence supporting modest weight loss when used with lifestyle changes.
All three medications must be prescribed by a licensed healthcare professional following a clinical assessment. Use our free GLP-1 weight loss calculator above to explore potential outcomes at different doses—results depend on individual response, dose, and adherence to lifestyle changes.
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 How to Access Weight Loss Meds
In the UK, adults may be eligible for prescription weight management medication if they have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower weights. Calculate your BMI using our free BMI calculator above to check your starting point.
NHS access: Referral to tier 3 specialist weight management services through your GP; availability varies significantly by region and waiting lists can be lengthy. Private access: Through licensed prescribers via online consultations, typically faster and without NHS referral. Your GP can discuss which route is most appropriate for you and your individual health 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.
Who is eligible for weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes or high blood pressure, may be eligible. Lower BMI thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. A prescriber will assess your individual eligibility following a clinical consultation. Pregnancy, breastfeeding, and certain medical conditions may exclude you.
How much weight can I lose with weight loss injections?
Clinical trials show average weight loss of 14–21% of body weight depending on the medication and dose, though results vary considerably between individuals. This typically means losing 10–30 kg over several months, but individual outcomes depend on adherence to medication, calorie reduction, physical activity, and personal metabolism. Our GLP-1 weight loss calculator can help estimate potential outcomes based on your starting weight.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Mounjaro has shown slightly higher average weight loss in trials, but both are effective. The choice depends on clinical assessment, personal response, and prescriber recommendation. Both are once-weekly injections; individual results vary significantly.
Can I get weight loss meds through the NHS?
Yes, the NHS funds tirzepatide (Mounjaro) and semaglutide (Wegovy) through tier 3 specialist weight management services. Access requires referral from your GP and varies by region. Waiting lists can be very long in many areas. Private prescribing is often faster but involves out-of-pocket costs. Your GP can discuss both options with you.
What happens after I stop taking weight loss medication?
Weight can gradually return if lifestyle changes (diet and physical activity) are not sustained. These medications support weight loss; they do not replace the need for long-term healthy habits. Many people continue medication longer-term to maintain progress. Your prescriber will discuss the most appropriate duration and follow-up plan based on your individual health and 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.