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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Diabetes Injections — A UK Health Guide
Diabetes injections, including GLP-1 receptor agonist medications, are prescription-only treatments that help manage blood sugar and support weight loss in people with type 2 diabetes. In the UK, several options are available through the NHS and private prescribing. This guide explains how they work, who can use them, and the key differences between medications like Ozempic and Wegovy. Understanding your options is the first step toward managing your health effectively. Our BMI calculator can help you assess your current health status as you explore treatment pathways with your GP.
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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.
How Diabetes Injections Work and What's Available
GLP-1 receptor agonist medications are the most commonly prescribed diabetes injections in the UK. They work by mimicking a natural hormone (GLP-1) that helps regulate blood sugar and appetite. This mechanism means these injections can provide dual benefits: improved blood sugar control and weight loss support.
- Ozempic (semaglutide) — Licensed for type 2 diabetes management at doses up to 2 mg once weekly. Helps lower blood sugar and may support modest weight loss as a side effect.
- Wegovy (semaglutide 2.4 mg) — The same medication but at a higher dose specifically licensed for weight management in UK adults. Clinical trials showed an average weight loss of approximately 14.9% of body weight alongside a reduced-calorie diet and increased physical activity.
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 agonist approved for both type 2 diabetes and weight management. In clinical trials, it achieved average weight loss of 15–21% of body weight.
All three are prescription-only and require a clinical assessment before being prescribed. Your GP or a licensed prescriber will determine which is most suitable based on your individual health needs and blood sugar control goals.
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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.
Key Differences and UK Eligibility
It's important to understand that Ozempic and Wegovy are not interchangeable, even though both contain semaglutide. Ozempic is approved for type 2 diabetes — using it for weight loss alone is off-label and not recommended. Wegovy is the licensed weight management version. In the UK, adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, may be eligible for prescription weight loss treatment. Access is available through NHS specialist tier 3 weight management services or private online prescribing following a clinical assessment. Use our free GLP-1 weight loss calculator to estimate potential results with different medications, and track your progress with our weight loss progress tracker. Individual results vary significantly — your GP or prescriber can discuss realistic expectations for your situation.
- 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 difference between Ozempic and Wegovy?
Both contain semaglutide, but Ozempic (up to 2 mg) is licensed for type 2 diabetes management, while Wegovy (2.4 mg) is licensed specifically for weight management in UK adults. Ozempic is not licensed for weight loss, and using it off-label for this purpose is not recommended. Wegovy is the appropriate choice if weight management is the primary goal.
Can I get diabetes injections through the NHS?
Yes. Ozempic for diabetes management is available through the NHS if your GP prescribes it for type 2 diabetes control. Weight management medications like Wegovy are typically available through NHS specialist tier 3 weight management services, though availability varies significantly by region and waiting lists can be lengthy. Private prescribing is also available following an online clinical assessment.
How much weight can I expect to lose with diabetes injections?
In clinical trials, Wegovy helped participants lose an average of 14.9% of body weight, and Mounjaro achieved 15–clinically studied weight loss. However, individual results vary significantly. Weight loss depends on your starting weight, diet, physical activity level, and how your body responds. Your prescriber can discuss realistic expectations based on your personal health profile.
Are diabetes injections safe for long-term use?
GLP-1 medications have been used safely for many years in diabetes management. Clinical trials support their safety and effectiveness. However, like all prescription medications, they can cause side effects including nausea, diarrhoea, and stomach pain, which usually decrease over time. Your GP or prescriber will monitor your health and discuss any concerns during treatment.
What is the difference between GLP-1 and GIP/GLP-1 medications?
GLP-1 agonists (like Wegovy and Ozempic) activate one hormone pathway. Dual GIP/GLP-1 agonists like Mounjaro activate two pathways, which may provide enhanced appetite suppression and weight loss. Clinical trials suggest Mounjaro may deliver slightly greater average weight loss, but individual responses vary. Your prescriber can advise which is most appropriate for you.
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.