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
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Mounjaro Weight Loss in Your First Month: UK Cost & Access
Mounjaro (tirzepatide) is a weekly weight loss injection licensed in the UK, but weight loss in the first month is typically modest because of the dose titration schedule. You'll start on 2.5 mg for weeks 1–4, then increase every 4 weeks. Most people see noticeable appetite changes within days, but significant weight loss usually takes 8–12 weeks. Understanding the UK cost, access routes, and what to expect in month one can help you make an informed decision about whether this prescription weight loss injection is right for you.
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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.
Cost and Access Routes for Mounjaro in the UK
Mounjaro is available through two main routes in the UK: NHS specialist weight management services and private online prescription services. NHS access is through tier 3/4 specialist centres following a GP referral, but availability varies significantly by region and waiting lists can be lengthy. Private access is faster — a licensed prescriber conducts an online clinical assessment, and if suitable, issues a prescription to a GPhC-registered pharmacy. Private costs typically range from £129–£320 per month depending on your starting dose and chosen provider. The 2.5 mg starting dose (lowest cost) covers your first 4 weeks, after which you may progress to higher doses if clinically appropriate. Many people find private access more practical if NHS waiting lists are extended in their area, though NHS treatment, where available, may be covered by your existing healthcare contributions.
- NHS route: free once prescribed, but may involve waiting lists
- Private route: faster access, typically £129–£320/month depending on dose
- Starting dose (2.5 mg) is the same regardless of route
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.
What to Expect in Month One and Beyond
During your first month on Mounjaro, you'll remain on the 2.5 mg starting dose, which allows your body to adjust. Many people report reduced appetite and food cravings within days, but average weight loss in month one is typically 1–3 kg — modest compared to later months when higher doses take effect. Your prescriber will review your response at week 4 before increasing to 5 mg (weeks 5–8). Real weight loss acceleration usually occurs from month two onwards as your dose increases. This gradual dose titration approach minimises side effects like nausea and diarrhoea. Our GLP-1 weight loss calculator can help you project potential weight loss across different doses and timeframes. Track your progress monthly using our free progress tracker to stay motivated and share results with your prescriber at review appointments.
- 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 can I expect to lose in the first month of Mounjaro?
Most people lose 1–3 kg in month one on the starting 2.5 mg dose, though this varies. Significant weight loss typically accelerates from month two onwards as your dose increases. Clinical trials showed average weight loss of 15–21% body weight over 72 weeks at higher maintenance doses.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose and provider. The starting 2.5 mg dose is at the lower end of this range. Prices may vary between private prescription services, so it's worth comparing.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS use through specialist tier 3/4 weight management services. Access requires a GP referral and eligibility assessment. Availability and waiting times vary significantly by region — your GP can advise on local services.
Is Mounjaro the same as a weekly weight loss injection?
Yes, Mounjaro is a once-weekly weight loss injection. It's a GIP and GLP-1 receptor agonist, different from Wegovy (a GLP-1-only injection) and other weight management medicines. Both are prescription-only and require clinical assessment.
What happens at week 4 if I'm on Mounjaro?
At week 4, your prescriber reviews your response to the 2.5 mg starting dose. If you've tolerated it well, your dose increases to 5 mg for weeks 5–8. This gradual dose titration helps minimise side effects while your body adjusts to the medication.
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.