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 to Tell If Weight Loss Is Working
Weight loss isn't always straightforward, and the scales don't tell the whole story. If you're on a weight management journey in the UK—whether through lifestyle changes, diet, or prescription medication—there are many signs that your efforts are working beyond just the number on the scales. Understanding these signs helps you stay motivated and assess whether your approach is effective for your health.
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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.
Signs Weight Loss Is Working Beyond the Scales
Several health markers indicate weight loss success before significant weight changes appear:
- Improved energy levels — you may notice increased stamina during daily activities and exercise
- Better sleep quality — weight loss often reduces sleep apnoea severity and improves rest
- Clothes fit differently — dropping a dress size or belt notch before major scale changes is common
- Reduced joint pain — less pressure on knees, hips, and lower back provides relief
- Improved blood pressure — your GP may notice lower readings at check-ups, even with modest weight loss
- Better blood sugar control — fewer energy crashes and steadier mood throughout the day
- Reduced bloating and indigestion — digestive comfort often improves early in weight loss
Even a 5–10% reduction in body weight produces measurable health benefits. You can track these changes using our free progress tracker to log both weight and how you feel physically, giving a fuller picture of your weight management progress. Calculate your personal BMI using our free BMI calculator to establish your starting point and monitor improvements in your health metrics over time.
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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.
Weight Management Medication Options Available in the UK
For adults who qualify, prescription weight management medication can support weight loss alongside lifestyle changes. Three medications are currently licensed for weight management in the UK:
- Mounjaro (tirzepatide) — a once-weekly injection that works as a dual GLP-1 and GIP receptor agonist
- Wegovy (semaglutide) — a once-weekly GLP-1 receptor agonist injection
- Saxenda (liraglutide) — a daily GLP-1 receptor agonist injection
In clinical trials, adults taking these medications lost an average of 14–21% of their body weight alongside a reduced-calorie diet and increased physical activity—results vary significantly between individuals. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses. Access through the NHS specialist weight management services or private prescribing following clinical assessment. Your GP can discuss whether prescription weight loss medication might be appropriate for your individual health profile.
- 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's the fastest way to tell if weight loss medication is working?
The first signs often appear within 2–4 weeks: reduced appetite, fewer food cravings, and feeling fuller after smaller meals. Changes in energy levels and sleep quality typically follow. Weight loss on the scales usually becomes noticeable after 4–8 weeks. Individual timelines vary significantly. Your GP or prescriber can monitor your progress with regular check-ins.
Does weight loss medication work better than diet and exercise alone?
Prescription weight loss medications are designed to work alongside, not instead of, lifestyle changes. Clinical trials show that medication plus diet and exercise produces greater average weight loss than either approach alone. However, results vary between individuals. Some people respond very well to medication; others see modest benefits. Your prescriber will assess what's most suitable for you.
How do I know if I'm eligible for weight loss medication on the NHS?
NHS eligibility typically requires a 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. For people of South Asian, Black African, Black Caribbean, or Chinese heritage, lower thresholds apply. Access is through specialist tier 3 weight management services via your GP. Availability varies significantly by region.
Can I get prescription weight loss medication privately in the UK?
Yes. Prescription weight loss medications are available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This doesn't require NHS referral. Costs typically range from £129–£320 per month depending on the medication and dose. Always ensure the prescriber is UK-licensed and the pharmacy is regulated.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual responses vary considerably. Your prescriber will recommend the most suitable option based on your health profile.
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.