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
Free tracker included with every download this week
Is Reta a Weight Loss Injection Available in the UK?
Reta is not currently a recognised weight loss injection available in the UK. You may be thinking of Wegovy (semaglutide) or Mounjaro (tirzepatide) — the two main prescription weight management injections licensed in the UK. Both are once-weekly injections that work by activating natural appetite-regulating hormones. This guide explains how these medications work, what to expect, and how to access prescription weight loss support in the UK through the NHS or private prescribing.
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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.
What Weight Loss Injections Are Actually Available in the UK?
Two main prescription weight loss injections are currently licensed in the UK:
- Wegovy (semaglutide) — a GLP-1 receptor agonist administered once weekly. In clinical trials (STEP-1), participants lost an average of approximately 15% of their body weight over 68 weeks when combined with a reduced-calorie diet and increased physical activity.
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, also once weekly. SURMOUNT trials showed average weight loss of 15–21% depending on dose.
Both are prescription-only medicines that require a clinical assessment before prescription. Eligibility typically includes a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure. The NHS recommends using our free GLP-1 weight loss calculator to estimate potential outcomes with these medications, though individual results vary significantly.
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.
How to Access Weight Loss Medication in the UK
Access through the NHS: Request a GP referral to a tier 3 specialist weight management service. Availability and waiting times vary significantly by region. Some areas have lengthy waiting lists.
Access through private prescribing: Registered online prescribers can issue prescriptions following a clinical assessment — you do not need an NHS referral. Prescriptions are dispensed by GPhC-registered pharmacies. This route is generally faster but involves private costs.
Before starting any weight loss medication, discuss your medical history, current medications, and health goals with your prescriber. These injections work alongside dietary changes and physical activity, not instead of them. Use our BMI calculator to check your current BMI and understand your starting point for weight management discussions with a healthcare professional.
- 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 Reta weight loss injection?
Reta is not a recognised weight loss injection in the UK. You may be searching for Wegovy (semaglutide) or Mounjaro (tirzepatide), which are the licensed prescription weight loss injections available. Both are GLP-1 or GIP/GLP-1 receptor agonists used for weight management in UK adults.
Are Wegovy and Mounjaro the only weight loss injections available in the UK?
No — Saxenda (liraglutide) is also licensed for weight management, though it is a daily injection rather than weekly. Wegovy and Mounjaro are the most commonly prescribed options due to their once-weekly dosing schedule.
Do I need to be referred by my GP to get a weight loss injection?
For NHS access, yes — your GP must refer you to a specialist weight management service. For private prescribing, no — you can access a private prescriber online without an NHS referral, though a clinical assessment is still required.
What is the difference between Ozempic and Wegovy?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (up to 2 mg) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version (up to 2.4 mg) and is specifically prescribed for weight loss in eligible adults.
How much weight can I expect to lose with these injections?
Clinical trials show average weight loss of 15–21%, but individual results vary significantly. Weight loss depends on the medication, dose, adherence, diet, and physical activity. Always discuss realistic expectations with your prescriber — results are not assured. ```
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.