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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Fat Reducing Injections in the UK
Fat reducing injections—often called weight loss jabs or slimming injections—are prescription-only medicines licensed in the UK for weight management in adults. These injectable medications work by mimicking natural hormones that regulate appetite and help you feel fuller after smaller meals. If you're considering this NHS health guidance route or exploring weight management options, it's important to understand how they work, who can access them, and what realistic expectations are.
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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 Fat Reducing Injections Work
Fat reducing injections currently available in the UK are GLP-1 receptor agonists (and in one case, a dual GIP/GLP-1 agonist). These medications mimic glucagon-like peptide-1, a natural hormone your gut produces after eating. This hormone signals to your brain that you feel full, which helps reduce appetite and food cravings.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection; clinical trials showed average weight loss of around 15% body weight alongside diet and exercise
- Mounjaro (tirzepatide) — a dual GIP/GLP-1 injection given once weekly; SURMOUNT trial data showed average weight loss of 15–21% depending on dose
- Saxenda (liraglutide) — a once-daily GLP-1 injection, an alternative option with established safety data
These injections also slow how quickly food moves through your stomach and can improve blood sugar control. Individual results vary significantly—weight loss depends on your starting weight, adherence to treatment, diet, and physical activity levels.
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
In the UK, fat reducing injections are prescription-only medicines available through two routes. NHS access: Referral to a specialist tier 3 weight management service from your GP, though availability varies by region and waiting lists can be lengthy. Private access: Online consultation with a UK-licensed prescriber through private services—faster but involves a cost of roughly £129–£320 monthly depending on dose and provider.
To be eligible, you typically need a BMI of 30 or above, or 27–29.9 with a weight-related health condition like type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to higher cardiovascular risk at lower weights. A prescriber will assess your suitability before issuing any prescription.
Use our free BMI calculator above to determine your current BMI category and see whether you might meet eligibility criteria. Our GLP-1 weight loss calculator can also help you estimate potential weight loss at different doses based on clinical trial data. These tools give you a starting point for discussion with your GP or a licensed prescriber.
Remember: prescription weight loss injections work best alongside a reduced-calorie diet and regular physical activity. They are not a replacement for lifestyle changes, but a support tool to help make those changes easier and more sustainable.
- 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.
Are fat reducing injections the same as Ozempic?
No. Ozempic contains semaglutide but is licensed for type 2 diabetes management. Wegovy also contains semaglutide but at a higher dose and is specifically licensed for weight management. Using Ozempic for weight loss is off-label. In the UK, Wegovy is the licensed weight loss version of semaglutide.
How much weight can I expect to lose with fat reducing injections?
Clinical trials show average weight loss of 15–21% body weight over approximately one year, depending on the medication and dose. However, individual results vary significantly. Weight loss depends on your starting weight, diet adherence, physical activity, and how your body responds. Always discuss realistic expectations with your prescriber.
What are the main side effects of fat reducing injections?
Very common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain—usually most noticeable when first starting or increasing doses. Most side effects tend to settle as your body adjusts. Serious side effects are rare but can include severe stomach pain (pancreatitis risk). Always report new or worsening symptoms to your GP or prescriber.
How much do fat reducing injections cost privately in the UK?
Private costs typically range from £129 to £320 per month depending on the medication, dose, and provider. Prices vary because different providers charge different fees for clinical assessments and dispensing. NHS access is free but involves waiting for referral to a specialist service, with regional variation in availability.
Can I get fat reducing injections on the NHS in the UK?
Yes, but access is through specialist tier 3 weight management services. You need a GP referral. Availability and waiting times vary significantly by region and NHS integrated care board (ICB). Some areas have shorter waits; others may have multi-month queues. Ask your GP about NHS weight management services in your area.
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.