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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Appetite Suppressant Injections in the UK
Appetite suppressant injections are prescription-only medications that can help reduce hunger and support weight management in UK adults. These injections, primarily GLP-1 receptor agonists, work by mimicking natural hormones that regulate appetite and food intake. They're available through both NHS specialist weight management services and private prescribing, but require a clinical assessment and must be used alongside dietary changes and increased physical activity. This UK health guide explains how they work, who can access them, and what to expect.
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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 Appetite Suppressant Injections Work in the UK
GLP-1 receptor agonist injections (and the newer dual GIP/GLP-1 agonists) mimic natural gut hormones that signal fullness to your brain. They slow how quickly food leaves your stomach, reduce cravings, and help you feel satisfied after smaller meals.
UK-licensed options include tirzepatide (Mounjaro) and semaglutide (Wegovy), both given once weekly. Clinical trials showed average weight loss of 15–21% body weight over 68–72 weeks, though individual results vary significantly.
- Mounjaro (tirzepatide): Dual GIP+GLP-1 agonist; doses 2.5–15 mg weekly
- Wegovy (semaglutide): GLP-1 agonist; doses 0.25–2.4 mg weekly
- Saxenda (liraglutide): Daily injection; doses 0.6–3 mg
These are prescription-only medicines requiring a clinical assessment before dispensing.
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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.
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UK Access and NHS Eligibility
In the UK, appetite suppressant injections are available through NHS specialist weight management services (tier 3/4) or private prescribing. NHS access typically requires GP referral and assessment, but availability varies significantly by region and waiting times can be lengthy.
Eligibility criteria include BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, sleep apnoea, or cardiovascular disease). Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to higher health risks at lower weights.
Use our free BMI calculator to check your current BMI and understand where you fall. Your GP can provide personalised guidance on whether prescription weight management is appropriate for you and which NHS pathway may be available in your area.
Private prescribing is available through GPhC-registered online pharmacies following an online consultation with a UK-licensed prescriber. Costs typically range from £129–£320 monthly depending on dose. Weight loss should be supported by a reduced-calorie diet and increased physical activity — injections work best as part of a comprehensive approach.
You can estimate potential weight loss at different doses using our free GLP-1 weight loss calculator, which helps you understand realistic outcomes. Track your progress over time with our free progress tracker to monitor both weight changes and other health improvements like energy levels or reduced joint pain.
- 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 appetite suppressant injections available on the NHS in the UK?
Yes. GLP-1 medications including Mounjaro and Wegovy are approved by NICE for use within NHS specialist weight management services (tier 3/4). However, access requires GP referral and varies significantly by region. Some areas have long waiting lists. Private prescribing is also available through online consultations with UK-licensed prescribers.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials showed slightly higher average weight loss with Mounjaro (~21% vs ~15%), but both are effective. Individual results vary. Your prescriber will assess which is most suitable for you.
What are the common side effects of appetite suppressant injections?
Very common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain — typically mild and improving over weeks. Less common are dizziness, headache, fatigue, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Discuss any concerns with your prescriber.
Do I need a prescription for appetite suppressant injections in the UK?
Yes. All GLP-1 and GIP/GLP-1 appetite suppressant injections are prescription-only medicines in the UK. You cannot purchase them without a valid prescription from a UK-licensed prescriber, whether through NHS services or private prescribing. Always ensure your prescriber is registered with the MHRA and your pharmacy is GPhC-registered.
How much weight can I expect to lose with these injections?
Individual results vary significantly based on starting weight, dose, adherence, diet, and physical activity. Clinical trials showed average weight loss of 15–21% body weight over 68–72 weeks. Some people lose more, others less. Weight loss is not assured. These injections work best alongside a reduced-calorie diet and increased physical activity, not as a standalone treatment.
Ready to take control of your weight loss journey?
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