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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Why Isn't Your 10mg Mounjaro Working?
If you've been taking Mounjaro at 10mg and aren't seeing the weight loss results you expected, you're not alone. Weight loss on tirzepatide varies significantly between individuals, and several factors may explain why you're not experiencing the progress you hoped for. This guide covers what you need to know about dose response, timing, and when to speak with your prescriber about next steps in the UK.
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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.
Understanding Mounjaro Response and Dose Escalation
Clinical trial data shows that 10mg Mounjaro produces average weight loss of around 19.5% of body weight over 72 weeks — but individual results vary considerably. Some people respond well at lower doses, while others benefit from escalating to 12.5mg or the maximum 15mg. You should have been on 10mg for at least 4 weeks before dose escalation was considered; if you've only recently reached this dose, it's still early to judge effectiveness.
Key factors affecting response include:
- Time on dose: Weight loss can take 8–12 weeks to become noticeable, even at the correct dose
- Diet and activity: Mounjaro works alongside reduced-calorie intake and physical activity — without these changes, results are limited
- Individual metabolism: Genetics, age, hormonal factors, and other medical conditions affect how your body responds
- Side effects masking results: Nausea and reduced appetite can sometimes mask early weight loss signals
- Medication interactions: Certain medicines may reduce tirzepatide effectiveness
Your prescriber may recommend escalating to 12.5mg or 15mg, or reviewing your overall approach to diet and exercise. Using our GLP-1 weight loss calculator can help you understand projected outcomes at different doses based on clinical trial data.
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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.
When to Contact Your Prescriber and NHS Options
If you've been on 10mg Mounjaro for 8+ weeks without any noticeable change, contact your prescriber or GP. NHS specialist weight management services (tier 3) will review whether you need dose escalation, a different medication like Wegovy (semaglutide), or additional support with diet and lifestyle changes. NICE guidance supports tirzepatide access through NHS services, though availability varies by region and waiting lists can be lengthy.
Private prescribing also remains an option if NHS access is limited in your area. Regardless of route, be honest with your prescriber about your diet, exercise, and side effects — this information helps them make the best decision for you. Track your progress using MyWeightCheck's free progress tracker to share concrete data at your next appointment, rather than relying on how you feel.
- 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 long does it take for 10mg Mounjaro to work?
Most people see noticeable weight loss within 8–12 weeks at a stable dose. However, the first few weeks often show no change or slight loss. Clinical trials measured results over 72 weeks, so patience is important. If you've been on 10mg for less than 8 weeks, continue as prescribed and monitor progress.
Should I move to 15mg if 10mg isn't working?
Potentially, but only under your prescriber's guidance. MHRA guidance recommends staying on each dose for at least 4 weeks before escalating. If you've been on 10mg for 8+ weeks with minimal results and diet/exercise are optimised, ask your prescriber about escalating to 12.5mg or 15mg.
Could my diet be the reason Mounjaro isn't working?
Yes — this is a common factor. Mounjaro works best alongside a reduced-calorie diet and regular physical activity. If you're eating at maintenance calories or above, weight loss will be minimal regardless of dose. A dietitian can help you create a sustainable calorie deficit.
What's the difference between 10mg Mounjaro and 10mg Wegovy?
These are different medications. Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist, while Wegovy (semaglutide) is GLP-1 only. Maximum Wegovy dose is 2.4mg, not 10mg. If Mounjaro isn't working, your prescriber might discuss switching to Wegovy, though individual response varies.
Can I check my BMI to see if Mounjaro should be working?
Your BMI doesn't determine Mounjaro effectiveness — individual factors do. However, you can use our free BMI calculator to track how your BMI changes as you lose weight, which gives concrete progress data to share with your prescriber at appointments.
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.