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 Appetite Suppressants Work for Weight Loss
Appetite suppressant medications can help reduce hunger and support weight loss by altering how your brain signals fullness. In the UK, prescription weight loss appetite suppressants work by mimicking natural hormones that regulate appetite. These medications are typically used alongside diet and exercise changes as part of a structured weight management approach. Understanding how they work, who can access them, and what the evidence shows can help you make informed decisions about weight management in the UK.
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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 GLP-1 Appetite Suppressants Work
GLP-1 receptor agonist medications are the most commonly prescribed appetite suppressants in the UK for weight management. They work by activating the GLP-1 hormone pathway, which naturally signals to your brain that you are full. This mechanism helps reduce food cravings, supports eating smaller portions, and may decrease overall hunger between meals.
Two prescription appetite suppressants are currently licensed in the UK: Wegovy (semaglutide) is a once-weekly injection, and Mounjaro (tirzepatide) is also once-weekly but uses a dual GIP and GLP-1 mechanism for potentially stronger appetite suppression. Clinical trials showed that on average, participants using these medications lost approximately 15–21% of their body weight alongside reduced-calorie diet and increased physical activity. Individual results vary significantly.
These medications also slow gastric emptying (how quickly food leaves your stomach), contributing to prolonged satiety. However, appetite suppressants work best when combined with lifestyle changes—they are not a substitute for healthy eating and movement habits.
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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
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Accessing Appetite Suppressants in the UK
Prescription appetite suppressant medications are available in the UK through two routes: NHS access via specialist tier 3/4 weight management services (typically with a referral from your GP), or private access through registered online prescribers following a clinical assessment. NHS availability and waiting times vary significantly by region.
Eligibility generally requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. A qualified prescriber will assess whether an appetite suppressant is suitable for your individual circumstances. Use our free BMI calculator above to check where your current weight sits, and our GLP-1 weight loss calculator to explore potential outcomes at different doses. Your GP remains the best first point of contact for discussing weight management options.
- 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 Wegovy and Mounjaro appetite suppressants?
Both are prescription-only once-weekly injections. Wegovy (semaglutide) is a GLP-1 agonist; Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. Clinical trials suggest both support appetite suppression and weight loss, though results vary individually. Mounjaro may offer slightly stronger appetite suppression due to its dual mechanism, but both require prescription and clinical assessment.
Can I get appetite suppressants on the NHS in the UK?
Yes, prescription appetite suppressants are available on the NHS through specialist weight management services (tier 3/4). Access requires a GP referral and assessment by a specialist. Availability and waiting times vary by region and local health board. Private prescribing is also available without an NHS referral through registered online providers.
How quickly will an appetite suppressant help me lose weight?
Weight loss typically becomes noticeable after 4–8 weeks of starting a prescription appetite suppressant, though individual timelines vary. Most people reach their maximum weight loss benefit around 16–20 weeks. Results depend on dose, diet changes, physical activity, and individual metabolism. Never expect assured outcomes—work with your prescriber to monitor progress.
Are appetite suppressants safe to use long-term?
Prescription appetite suppressants like Wegovy and Mounjaro have been studied in clinical trials lasting up to 68 weeks or longer. They appear safe in the short to medium term for eligible individuals without contraindications. Long-term safety data is still being gathered. Always discuss risks, benefits, and your medical history with your GP or prescriber before starting.
What is the difference between appetite suppressants and other weight loss medications?
GLP-1 and GIP/GLP-1 appetite suppressants work by signalling fullness and reducing hunger. Other mechanisms exist—for example, orlistat reduces fat absorption in the digestive system. Appetite suppressants are generally more effective for weight loss than other medication types, based on clinical evidence. Your prescriber will recommend the most suitable option for your circumstances.
Ready to take control of your weight loss journey?
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