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 Mounjaro Works for Weight Loss in the UK
Mounjaro (tirzepatide) is a prescription-only weekly injection licensed in the UK for weight management in adults. Unlike a simple "recipe", Mounjaro works by activating two natural hormone pathways—GIP and GLP-1—which help regulate appetite and support feeling fuller after meals. It's prescribed alongside a reduced-calorie diet and increased physical activity, not as a replacement for lifestyle changes. Access in the UK is through NHS specialist tier 3 weight management services or private prescription following clinical assessment. Understanding how it fits into your health journey is essential before starting.
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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.
NHS Eligibility and NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services for eligible adults. You may be considered for NHS Mounjaro if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply—eligibility may start at BMI 27.5.
However, NHS access is typically through tier 3 specialist weight management services, not from your GP directly. You'll need referral from your primary care team, and availability varies significantly across regions. Waiting lists can be several months or longer in many areas. In clinical trials, Mounjaro at the maximum 15 mg dose helped participants lose an average of approximately 20.9% of their body weight over 72 weeks—though individual results vary widely. The weekly weight loss injection is started at a low dose (2.5 mg) and gradually increased every 4 weeks to find the dose that works best for you, a process called dose titration.
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 Mounjaro Routes in the UKPrivate Mounjaro Access and Next Steps
If NHS waiting times are long in your area, private prescription is an alternative route. Mounjaro is available through GPhC-registered online pharmacies in the UK following a consultation with a UK-licensed prescriber. Private costs range from approximately £150–£300 per month depending on the dose. Both routes require clinical assessment—your prescriber will review your medical history, current medications, and weight management goals to confirm suitability. Regardless of route, Mounjaro is always used alongside dietary changes and physical activity for best results. Use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and track your progress with our free progress tracker once you start treatment.
- 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.
Can I get Mounjaro on the NHS in the UK?
Yes—NICE has approved Mounjaro for NHS use. However, access is through specialist tier 3 weight management services, not standard GP prescription. You'll need referral from your GP and must meet BMI and health criteria. Waiting lists vary by region and can be several months long.
What is dose titration with Mounjaro?
Dose titration is the gradual increase of your Mounjaro dose every 4 weeks, starting at 2.5 mg and moving up to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg. Your prescriber adjusts based on your response and tolerance. Most people reach an effective dose before reaching 15 mg.
How much weight can I expect to lose with Mounjaro?
Clinical trials showed average weight loss of approximately 15–21% of body weight over 72 weeks at maintenance doses. However, results vary significantly between individuals. Weight loss also depends on your diet, physical activity, and how your body responds. Your GP can discuss realistic expectations.
Is Mounjaro the same as Wegovy or Ozempic?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are licensed for weight management in the UK. Ozempic is also semaglutide but approved for type 2 diabetes, not weight loss. Mounjaro and Wegovy are different mechanisms with different clinical trial outcomes.
What happens if I miss a Mounjaro injection?
If you miss your weekly injection, take it within 4 days and continue your normal schedule. If more than 4 days have passed, skip that dose and take your next injection on your regular day. Never take a double dose. Contact your prescriber if you're unsure.
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.