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
Weekly Weight Loss Chart and UK Prescription Weight Management
A weekly weight loss chart helps you track progress towards your goals, but realistic expectations depend on your approach. The NHS recommends losing 0.5–1 kg per week for sustainable results. For eligible adults, prescription weight management medications like Mounjaro and Wegovy are now available in the UK and may support weight loss alongside lifestyle changes. This guide explains UK-licensed options, how they work, and how to find out if you're eligible for prescription support. Track your progress using our free weight loss calculator and BMI calculator to monitor changes over time.
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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.
UK-Licensed Prescription Weight Loss Medications
Three prescription medications are currently licensed in the UK for weight management in eligible adults:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly. Clinical trials showed average weight loss of 15–21% of body weight, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, injected once weekly. Average weight loss in trials was approximately 15% of body weight alongside reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 agonist, injected once daily. Available for eligible adults, though less commonly prescribed than weekly options.
Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Your GP or a licensed prescriber will assess whether prescription weight loss medication is suitable for you based on your individual health profile.
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 and Getting Started
NHS access: Prescription weight management medications may be available through NHS specialist tier 3 weight management services, typically accessed via GP referral. Availability and waiting times vary significantly by region and ICB. Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, without requiring NHS referral. Both routes require a prescription.
The first step is always to speak with your GP about your weight management goals. They can assess your eligibility, discuss whether prescription medication might help, and guide you towards appropriate support — whether NHS specialist services or private options. Our free GLP-1 weight loss calculator can help you explore potential outcomes with different medications and doses. Use our BMI calculator to establish your starting point, and our progress tracker to monitor weekly changes.
- 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 a realistic weekly weight loss rate with prescription medication?
The NHS recommends 0.5–1 kg per week for sustainable weight loss. With GLP-1 or dual GIP/GLP-1 medications, some people lose more initially, but this varies considerably. Clinical trials showed average weight loss of 15–21% over several months, not per week. Your prescriber will discuss realistic expectations for your individual situation.
How quickly do Mounjaro and Wegovy show results?
Weight loss typically begins within the first 2–4 weeks, but most significant results appear after 8–12 weeks of treatment. Doses are increased gradually over several weeks, so full effect takes time. Patience and consistency with lifestyle changes are essential for best outcomes.
Who is eligible for prescription weight loss medication on the NHS?
Generally, adults with a BMI of 30 or above, or 27 or above with weight-related conditions (diabetes, hypertension, cardiovascular disease), may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. Eligibility is assessed individually by your GP or specialist.
Can I get prescription weight loss medication privately if the NHS has a waiting list?
Yes. Private UK-licensed prescribers can assess and prescribe Mounjaro and Wegovy following an online consultation. This option is available without NHS referral but requires meeting the same clinical eligibility criteria and passing a health assessment.
Do I still need to diet and exercise if I'm taking prescription weight loss medication?
Yes. Prescription medications are most effective alongside a reduced-calorie diet and increased physical activity. Medication supports appetite control and feelings of fullness, but sustainable weight loss requires lifestyle changes. Your prescriber or a weight management professional can guide you on diet and exercise strategies.
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.