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
Why Is Your Weight Loss Slow On Mounjaro?
If you're experiencing slow weight loss on Mounjaro, you're not alone — results vary significantly between individuals. Weight loss with this weekly weight loss injection depends on dose, lifestyle changes, adherence, and individual metabolism. This guide explains what affects your progress, how to access Mounjaro in the UK, and what costs you can expect through NHS or private prescription routes.
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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 Private Prescription Costs & Access Routes
In the UK, Mounjaro (tirzepatide) is available through two main routes: NHS specialist services or private online prescribing. Private prescription costs vary by dose and provider, typically ranging from £129 to £320 per month depending on whether you're on a lower starting dose or the maximum 15mg dose. Each KwikPen contains four weekly injections, so monthly costs reflect your current dose titration stage. Important: Mounjaro is prescription-only and requires a clinical assessment before any prescription is issued — a UK-licensed prescriber will evaluate your BMI, health history, and suitability.
Private providers use secure online consultations; your prescriber reviews your medical background and determines whether this medication is appropriate for you. If approved, your prescription is sent to a GPhC-registered pharmacy for dispensing. Costs do not include delivery, which is typically £5–£10. Compare your GLP-1 weight loss options — our free GLP-1 calculator can help you estimate potential outcomes at different doses.
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 Access vs Private: Timeline & Eligibility
NHS route: Access through tier 3 specialist weight management services requires a GP referral. Eligibility: BMI 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea). NHS provision is free but availability varies dramatically by region — some areas have waiting lists of 6–18 months. Once assessed by the specialist service, Mounjaro may be prescribed alongside a reduced-calorie diet and increased physical activity.
Private route: Faster access (often within 1–2 weeks), no GP referral needed, available without NHS tier 3 assessment. Costs apply immediately. Both routes require ongoing clinical monitoring — your prescriber will check your progress and adjust your Mounjaro dose titration schedule based on tolerance and results. Track your own progress using our free progress tracker to monitor weekly weight 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.
Why is my weight loss so slow on Mounjaro compared to others?
Individual results vary significantly — factors include starting dose, current dose stage (dose titration takes weeks), adherence to reduced-calorie diet, physical activity level, metabolism, age, and medical conditions like PCOS or thyroid issues. Clinical trials showed average weight loss of 15–21% over 72 weeks, but some people lose faster or slower. Your prescriber can review your progress.
How much does Mounjaro cost on private prescription in the UK?
Private Mounjaro costs typically range from £129 to £320 per month depending on your current weekly weight loss injection dose. Starting doses (2.5–5mg) are usually cheaper; maximum dose (15mg) is more expensive. Costs vary between providers. Check with your prescriber for exact pricing at your current dose stage.
Can I get Mounjaro through the NHS in the UK?
Yes, if eligible. You need a GP referral to a tier 3 specialist weight management service. Eligibility: BMI 30+, or 27–29.9 with weight-related health conditions. NHS provision is free but regional availability varies — some areas have long waiting lists. Private prescription offers faster access without NHS referral.
What's the difference between NHS and private Mounjaro prescription?
NHS: free, requires GP referral and tier 3 assessment, longer wait times, prescribed alongside lifestyle support. Private: costs apply (£129–£320/month), faster access (1–2 weeks), no referral needed, online clinical assessment. Both require prescription from a UK-licensed prescriber and monitoring of your mounjaro kwikpen use and progress.
How often do I need clinical check-ins with private Mounjaro?
Private prescribers typically review your progress every 4–12 weeks, depending on your dose titration stage and how you're responding. Your prescriber will assess whether to continue, adjust your weekly weight loss injection dose, or switch medications. Regular monitoring ensures your mounjaro dose titration is safe and you're achieving expected results alongside diet and exercise changes.
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.