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
What Is an Appetite Suppressant Injection?
An appetite suppressant injection is a prescription-only weight management medication that works by activating natural hormone pathways in your body. In the UK, the most commonly prescribed appetite suppressant injection is Wegovy (semaglutide), a once-weekly GLP-1 receptor agonist. These medications may help reduce hunger, increase feelings of fullness, and support weight loss when combined with healthy diet and exercise. They are available through NHS specialist weight management services or private prescribers following a clinical assessment.
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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 Appetite Suppressant Injections Work
Appetite suppressant injections contain GLP-1 receptor agonists — medications that mimic a natural hormone called GLP-1 (glucagon-like peptide-1), which your body produces after eating. This hormone signals your brain that you are full, slows how quickly food leaves your stomach, and helps regulate appetite.
When you use an appetite suppressant injection, it amplifies these natural signals, meaning you may:
- Feel fuller after eating smaller portions
- Experience reduced cravings between meals
- Feel less hungry overall
- Have improved control over food choices
The effect typically begins within days of starting the medication. In clinical trials, Wegovy helped participants lose an average of approximately 15% of their body weight over 68 weeks alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly. Use our free GLP-1 weight loss calculator to see estimated projections at different doses.
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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.
UK Eligibility and How to Access
You may be eligible for an appetite suppressant injection in the UK if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or heart disease). If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights.
Access routes: NHS specialist weight management services can prescribe appetite suppressant injections, though waiting lists vary by region. Private online prescribers offer faster access following an online clinical assessment. Your GP can discuss which option suits you. Use our BMI calculator to check your starting point and explore whether you may be eligible.
- 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 an appetite suppressant injection and other weight loss medications?
Appetite suppressant injections like Wegovy use GLP-1 receptor agonists to reduce hunger and increase fullness. Other weight loss approaches include oral medications, very low calorie diets, or NHS weight loss programmes. Injections offer once-weekly dosing and strong clinical evidence for weight loss (approximately 15% body weight in trials). Your GP can discuss which approach suits your health and circumstances.
Is an appetite suppressant injection the same as Ozempic?
Both Ozempic and Wegovy contain semaglutide, but they are different. Ozempic is approved for type 2 diabetes management (doses up to 2mg). Wegovy is the licensed weight management version (doses up to 2.4mg). Wegovy is the appropriate prescription for appetite suppression and weight loss; Ozempic is not licensed for weight loss in the UK.
How quickly will I lose weight with an appetite suppressant injection?
Weight loss typically begins within 2–4 weeks and continues gradually as your dose increases. Clinical trials show average weight loss of approximately 15% of body weight over 68 weeks. However, individual results vary significantly based on diet, exercise, metabolism, and other factors. Sustainable loss is typically 0.5–1kg per week.
What are the common side effects of appetite suppressant injections?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — these often improve within a few weeks. Common side effects include indigestion, headache, fatigue, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always inform your prescriber of any side effects.
Can I get an appetite suppressant injection on the NHS?
Yes, NHS specialist tier 3 weight management services can prescribe appetite suppressant injections if you meet eligibility criteria. Access varies by region and waiting lists can be lengthy. Your GP can refer you to the specialist service in your area. Private prescribers also offer faster access following an online assessment and prescription through a GPhC-registered pharmacy.
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.