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
Average Weekly Weight Loss on Mounjaro in the UK
Most people taking Mounjaro lose approximately 0.5 to 1.5 kg per week, though this varies significantly between individuals and depends on dose, diet, and exercise. Clinical trials showed average weight loss of 15–21% of body weight over several months when used alongside a reduced-calorie diet and increased physical activity. Weekly loss tends to be modest at starting doses but increases as the dose escalates. Understanding what to expect — both in terms of weight loss and cost — helps you decide whether this prescription injection is right for you.
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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.
Weekly Weight Loss Expectations and Cost Context
Weekly weight loss averages: Clinical trials of Mounjaro showed participants lost approximately 0.5–1.5 kg per week, though some weeks show no loss and others show more. This is not assured and depends entirely on individual metabolism, calorie intake, and physical activity.
UK prescription costs: Private prescriptions for Mounjaro through online prescribers typically cost £120–£280 per month depending on dose, with 2.5 mg (starting dose) at the lower end and 15 mg (maximum dose) at the upper end. NHS access is available through specialist tier 3 weight management services but availability is very limited in many regions, with waiting lists often exceeding 12 months. Dose titration matters: you start on 2.5 mg weekly and increase every 4 weeks, so your early weekly weight loss may be lower than your loss once you reach maintenance doses of 10–15 mg.
Use our GLP-1 weight loss calculator to estimate projected weight loss at different doses and timeframes based on clinical trial data.
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 Mounjaro in the UK
NHS route: GP referral to your local tier 3 specialist weight management service. You must meet NICE criteria (BMI ≥30, or BMI 27–29.9 with weight-related health conditions). Once referred, you'll have a clinical assessment and be added to a waiting list. Many regions have significant delays. NHS prescription is free once approved.
Private route: Online consultation with a UK-licensed prescriber through GPhC-registered pharmacies. The process takes 24–48 hours from consultation to prescription. You'll answer a health questionnaire, have a consultation (usually asynchronous), and receive a prescription if clinically appropriate. Private costs range £120–£280 monthly depending on dose and provider. You'll also need to track your weight loss using tools like our free progress tracker to show your prescriber your response.
- 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.
How much weight does the average person lose per week on Mounjaro?
Clinical trials showed participants lost approximately 0.5–1.5 kg per week on average, though individual results vary significantly. Weight loss accelerates as the dose increases (you start at 2.5 mg and escalate over 16+ weeks). Some weeks show no loss, others show more. Consistent diet and exercise are essential for results.
Is Mounjaro available on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS specialist weight management services (tier 3). However, availability is very limited and waiting lists are long in many regions — often 12+ months. Your GP can refer you if you meet NICE eligibility criteria (BMI ≥30 or BMI 27–29.9 with comorbidities). Private prescriptions are accessible much faster.
How much does Mounjaro cost in the UK privately?
Private Mounjaro prescriptions typically cost £120–£280 per month depending on dose. Starting doses (2.5 mg) are cheaper; maintenance doses (10–15 mg) cost more. Costs vary between GPhC-registered pharmacies. NHS prescriptions are free once approved through specialist services, but waiting times can be very long.
What's the difference between accessing Mounjaro on the NHS versus privately?
NHS access requires a GP referral and assessment by a specialist tier 3 weight management service — free but with long waiting lists. Private access is faster (24–48 hours from consultation to prescription) but costs £120–£280 monthly. Both routes require a clinical assessment to confirm the medication is suitable for you.
How do I get a private Mounjaro prescription in the UK?
Consult with a UK-licensed prescriber through an online consultation platform. You'll complete a health questionnaire, have an assessment, and receive a prescription if clinically appropriate. The prescription is then dispensed by a GPhC-registered pharmacy. The entire process typically takes 24–48 hours from consultation to delivery.
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.