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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Best Weight Loss Injections Available in the UK
Weight loss injections are prescription-only medications that can support weight management when used alongside diet and exercise. In the UK, three main injectable medications are licensed for weight management: Wegovy (semaglutide), Mounjaro (tirzepatide), and Saxenda (liraglutide). All work by mimicking natural hormones that regulate appetite and blood sugar. Eligibility depends on your BMI and health conditions, and access is available through both NHS specialist services and private prescription. This guide explains how these injections work, what the evidence shows, and how to access them in the UK.
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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 Licensed in the UK?
Three prescription weight loss injections are currently licensed for use in the UK:
- Wegovy (semaglutide) — A once-weekly GLP-1 receptor agonist injection. Clinical trials (STEP-1) showed participants lost an average of approximately 15% of their body weight at the highest dose (2.4 mg) over 68 weeks, alongside a reduced-calorie diet and increased physical activity.
- Mounjaro (tirzepatide) — A once-weekly dual GIP and GLP-1 receptor agonist. In the SURMOUNT-1 trial, participants lost an average of 20.9% of their body weight at the maximum dose (15 mg) over 72 weeks with lifestyle changes.
- Saxenda (liraglutide) — A daily GLP-1 injection. Evidence shows modest weight loss of approximately 5–10% of body weight.
All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly based on adherence, lifestyle changes, and personal factors.
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.
UK Eligibility and How to Access Weight Loss Injections
In the UK, you may be eligible for prescription weight loss injections if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage.
NHS access: Referral to a tier 3 specialist weight management service through your GP. Availability and waiting times vary by region.
Private access: Online consultation with a UK-licensed prescriber, available without NHS referral. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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.
Which weight loss injection is "best" in the UK?
There is no single "best" injection — the most suitable depends on your individual health profile, BMI, and medical conditions. Wegovy and Mounjaro both have strong clinical evidence. A prescriber will assess which is appropriate for you following a consultation. Results vary between individuals.
How much weight can you lose with weight loss injections?
Clinical trials show average weight loss of 15–21% of body weight over several months, depending on the medication and dose. However, individual results vary significantly. Weight loss is achieved alongside a reduced-calorie diet and increased physical activity — injections work best as part of a lifestyle approach.
Are weight loss injections available on the NHS in the UK?
Yes, Mounjaro and Wegovy are approved by NICE and available through NHS specialist weight management services. Access requires referral from your GP to a tier 3 service. Availability varies by region and waiting lists can be lengthy. Private access is also available through online prescribers.
What are the main side effects of UK weight loss injections?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — typically most noticeable when starting or increasing doses. These often improve over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and serious allergic reactions. Always report concerns to your prescriber.
Can you use weight loss injections long-term in the UK?
Yes, weight loss injections can be used long-term if they continue to be appropriate and effective. However, they are intended to be used alongside sustained lifestyle changes (diet and exercise). If you stop taking the injection, weight loss may reverse. Your prescriber will review your progress regularly. ```
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.