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
How Much Are Slimming Injections in the UK?
Slimming injections โ also called weight loss injections or fat jabs โ are prescription-only medicines that help regulate appetite and support weight management. In the UK, three GLP-1 weight loss injections are licensed for adults with obesity or overweight with health conditions. Costs vary significantly depending on which medication, dose, and whether you access them through the NHS or privately. Understanding what these injections are, how they work, and the costs involved can help you make an informed decision about weight management options available to you.
10,000+ calculations today ยท NHS-aligned thresholds ยท 100% free
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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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.
Three UK-Licensed Slimming Injections Explained
Three prescription-only weight loss injections are currently licensed in the UK for weight management in adults:
- Mounjaro (tirzepatide) โ A dual GIP and GLP-1 receptor agonist. Starts at 2.5 mg and increases to a maximum of 15 mg once weekly. In clinical trials, participants lost an average of 15โ21% of their body weight alongside diet and exercise changes.
- Wegovy (semaglutide) โ A GLP-1 receptor agonist. Doses range from 0.25 mg up to 2.4 mg once weekly. Clinical trial data showed an average weight loss of approximately 15% of body weight at the maximum dose.
- Saxenda (liraglutide) โ A GLP-1 receptor agonist given as a daily injection rather than weekly. Doses increase from 0.6 mg to a maximum of 3 mg per day. Results are comparable to other GLP-1 options.
All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly, and these medicines work best alongside a reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to see projected results at different doses.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care โ 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 โ 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 โ completely free.
How Slimming Injections Work โ The GLP-1 Mechanism
Slimming injections work by mimicking a natural hormone called GLP-1 (glucagon-like peptide-1), which your gut produces after eating. This hormone signals your brain that you are full, reduces cravings, and slows how quickly food leaves your stomach. By activating GLP-1 receptors, these weight loss injections help you feel fuller after smaller meals, eat less overall, and reduce the urge to snack between meals.
Importantly, slimming injections are not cosmetic injections โ they are prescription medical treatments that require a GP or licensed prescriber to assess whether they are appropriate for you. They work best when combined with lifestyle changes: a balanced, reduced-calorie diet and regular physical activity produce the best results. Track your weight loss progress with our free progress tracker to monitor changes over time.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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.
How much do slimming injections cost in the UK?
Private costs vary by medication and dose, typically ยฃ129โยฃ320 per month. NHS access is through specialist weight management services and depends on your local area. Mounjaro and Wegovy are more widely available privately than through the NHS. Always check current pricing with providers, as costs change regularly.
Can I get slimming injections on the NHS?
Yes, but access is limited. NICE has approved tirzepatide (Mounjaro) for NHS use within specialist tier 3 weight management services. However, availability varies significantly by region, and waiting lists can be very long. Ask your GP about referral to local specialist weight management services.
Are slimming injections the same as Ozempic?
No. Ozempic is a different brand of semaglutide approved for type 2 diabetes (doses up to 2 mg). Wegovy is the licensed weight management version of semaglutide (up to 2.4 mg). They are not interchangeable, and using Ozempic for weight loss is off-label in the UK.
What are slimming injections made of?
Slimming injections contain active pharmaceutical ingredients that are GLP-1 receptor agonists (or dual GIP/GLP-1 agonists in the case of Mounjaro). They are manufactured by pharmaceutical companies: Novo Nordisk makes Wegovy and Saxenda, and Eli Lilly makes Mounjaro.
Do I need a prescription for slimming injections?
Yes, all three UK-licensed weight loss injections are prescription-only medicines. You need an assessment by a UK-licensed prescriber (GP, specialist, or private prescriber) who will check whether the medication is safe and appropriate for your individual health before issuing a prescription. ```
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.