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
Can Caffeine Help Weight Loss?
Caffeine may have modest effects on metabolism and energy, but the evidence for significant weight loss is limited. For sustainable weight management in the UK, many eligible adults benefit from a combination of lifestyle changes and, where appropriate, prescription weight loss medication. If you're exploring weight management options, it's worth understanding both dietary factors like caffeine and the clinical approaches available through the NHS or private prescribing.
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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/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.
Prescription Weight Loss Options Available in the UK
If you're looking for evidence-based weight management beyond dietary supplements, three prescription medications are licensed in the UK for weight loss support:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly. Clinical trials showed average weight loss of 15–21% body weight over 72 weeks.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, injected once weekly. Evidence suggests average weight loss of around 15% body weight.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, injected daily. Similar weight loss support to Wegovy.
These medications work by helping regulate appetite and blood sugar control. You may be eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions. Calculate your BMI using our free BMI calculator to see where you stand. Individual results vary, and these medications are always used alongside lifestyle changes, not instead of them.
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.
NHS vs Private Access — How to Get Started
In the UK, prescription weight loss medication is available through two routes. NHS access is through specialist tier 3 weight management services — typically after GP referral — though waiting lists vary significantly by region and availability can be limited. Private access is available through licensed online prescribers following a clinical assessment, without needing an NHS referral.
Your GP can discuss whether prescription weight loss treatment is suitable for your circumstances and health history. If you're interested in exploring weight loss injections or other prescription options, a GP conversation is the best starting point. You can also use our free GLP-1 weight loss calculator to understand how these medications might support your goals.
- 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.
Does caffeine really help with weight loss?
Caffeine may increase metabolism slightly and boost energy for exercise, but the effect is modest. Most research shows caffeine alone produces minimal weight loss — typically less than 1–2 kg over several months. For sustainable weight management in the UK, combining caffeine consumption with a calorie deficit, regular physical activity, and (if eligible) prescription medication offers stronger evidence.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with average weight loss around 15–21% in trials. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Both require prescription and clinical assessment. Individual results vary, and choice depends on your health history and prescriber assessment.
Am I eligible for prescription weight loss medication on the NHS?
Possible eligibility includes: BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Access varies by region and waiting lists can be lengthy. Your GP can assess your individual circumstances and refer you to specialist services if appropriate.
How quickly does prescription weight loss medication work?
Results take time. Mounjaro and Wegovy typically show noticeable weight loss within 8–12 weeks, with maximum benefit around 16–20 weeks on the final dose. However, individual timelines vary. These medications work best alongside a reduced-calorie diet and regular physical activity — they're a tool to support your efforts, not a substitute for lifestyle changes.
Can I get prescription weight loss medication privately in the UK?
Yes. Private online prescribers offer Mounjaro and Wegovy following an online clinical assessment. This route doesn't require NHS referral and availability is generally faster than NHS services. Costs vary by dose and provider (typically £130–£320+ per month). A UK-licensed prescriber will assess whether the medication is suitable based on your health history.
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.