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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Quick Weight Loss Help: Prescription Options Available in the UK
If you're looking for quick weight loss help in the UK, prescription weight management medications may be an option worth discussing with your GP. Three medicines are currently licensed for weight management in the UK: Mounjaro, Wegovy, and Saxenda. These prescription-only medications work alongside lifestyle changes to support weight loss in eligible adults. To find out if you qualify, you'll need a clinical assessment from a healthcare professional. This guide explains how UK weight management works, who is eligible, and how to access treatment through the NHS or privately.
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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 Management Medications: What's Available
Three prescription-only medicines are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, given once weekly by injection. Clinical trials showed average weight loss of 15–21% of body weight at the highest doses, though results vary between individuals.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also given once weekly by injection. Clinical evidence suggests average weight loss of around 15% of body weight, alongside reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, given by daily injection rather than weekly. It is typically used when weekly options are not suitable.
All three are prescription-only and require a clinical assessment before being prescribed. They are not available over the counter and are not supplied by high street pharmacies without a valid prescription.
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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.
Who Qualifies and How to Access Weight Loss Medication in the UK
In the UK, you may be eligible for prescription weight loss medication if you 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 heart disease. Lower BMI thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower weights.
You can access these medications through two routes: NHS specialist weight management services (through referral from your GP, though waiting times vary significantly by region), or private prescribing (via online consultation with a UK-licensed prescriber). Use our free BMI calculator above to check your starting point, then speak with your GP about the best route for you.
- 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 fastest way to get weight loss medication prescribed in the UK?
Private online prescribing is typically faster than NHS routes, which may have waiting lists. However, NHS access is available through specialist tier 3 weight management services if you are eligible. Your GP can assess whether you meet eligibility criteria and discuss both options with you. Prescription weight loss medication works best alongside reduced-calorie diet and increased physical activity — there are no shortcuts to sustainable weight loss.
Are GLP-1 weight loss injections available on the NHS?
Yes, Mounjaro and Wegovy are available through NHS specialist weight management services, though availability and waiting times vary significantly by region and ICB. Access is typically through a referral from your GP to a tier 3 or tier 4 specialist service. Private access is also available without NHS referral if you meet clinical criteria and wish to proceed privately.
What is the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss (15–21%) than Wegovy (around 15%) in clinical trials, but individual results vary significantly. Both are once-weekly injections. Your prescriber will assess which is most suitable for your health profile.
Is prescription weight loss medication safe?
Prescription weight loss medications are licensed and approved by the MHRA for use in the UK, meaning they have undergone rigorous safety testing. However, all medicines can cause side effects. The most common are nausea, diarrhoea, and constipation, which usually improve over time. Serious side effects are rare but possible. A healthcare professional will assess whether weight loss medication is safe and appropriate for you before prescribing.
Can I use weight loss injections if I have type 2 diabetes?
Yes, if you have type 2 diabetes and meet BMI criteria, you may be eligible for prescription weight loss medication. However, diabetes medications may need adjustment when starting weight loss injections — your GP or prescriber will monitor this carefully. Always inform your healthcare provider of all medications and health conditions before starting treatment.
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.