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 7.5 Not Working — What You Need to Know
If you've been taking Mounjaro 7.5mg for several weeks and haven't noticed any appetite suppression or weight loss, you're not alone. Many people find that their body adapts to a dose, or that a particular strength simply isn't optimal for them. This guide explains why Mounjaro 7.5 may not be delivering results, what steps you can take, and how to discuss your concerns with your prescriber in the UK healthcare system. Individual responses to tirzepatide vary significantly, and adjustments are often normal and expected.
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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.
Why Mounjaro 7.5 May Not Be Working for You
There are several reasons why Mounjaro 7.5 may not be producing the weight loss or appetite suppression you expected:
- Tolerance: Your body may have adapted to the dose after several weeks. GLP-1 and GIP receptor sensitivity can decrease over time for some people, requiring an increase to 10mg or 12.5mg to regain effectiveness.
- Insufficient time on dose: NICE and NHS guidance recommends staying on each Mounjaro dose for at least 4 weeks before assessing effectiveness. If you've only been on 7.5mg for 2–3 weeks, your body may still be adjusting.
- Lifestyle factors: Mounjaro works alongside reduced-calorie diet and increased physical activity — it's not effective without these changes. If dietary habits or activity levels have slipped, results will plateau.
- Individual variation: Clinical trials show tirzepatide works well on average, but some people naturally respond better to higher doses (10mg, 12.5mg, or 15mg maximum).
- Injection technique or storage: Improper storage (freezing a KwikPen, or storing above 30°C after first use) or incorrect injection technique can reduce effectiveness.
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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.
Next Steps — When to Speak to Your Prescriber
If you've been on Mounjaro 7.5mg for 4+ weeks with no noticeable effect, contact your prescriber — whether NHS or private — to discuss a dose increase. Never increase your dose yourself. Your prescriber may recommend stepping up to 10mg, 12.5mg, or the maximum 15mg dose based on your individual response and health profile.
If you're accessing Mounjaro through NHS tier 3 specialist weight management services, discuss your concerns at your next appointment. If through private online prescribing, message your prescriber with details of when you started the dose, your weight, any side effects, and whether you've been following dietary and activity guidance. Your prescriber can also rule out medical factors (medication interactions, thyroid issues, or metabolic conditions) that might affect 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 long should I wait before saying Mounjaro 7.5 isn't working?
NHS guidance recommends staying on each Mounjaro dose for at least 4 weeks before assessing effectiveness. This allows time for your body to adjust to the medication. If you've been on 7.5mg for less than 4 weeks, give it more time. If it's been longer and there's no noticeable appetite reduction, contact your prescriber about a dose increase.
Will moving to Mounjaro 10mg work if 7.5 is not working?
Many people respond better to higher doses of tirzepatide. Clinical data shows that moving from 7.5mg to 10mg, 12.5mg, or 15mg often produces better results for those who haven't seen expected appetite suppression or weight loss. Your prescriber will assess whether a dose increase is appropriate for you and can increase the dose at your next review.
Could my Mounjaro KwikPen be faulty or stored incorrectly?
Yes — improper storage can reduce effectiveness. Store unopened pens in the fridge at 2–8°C. After first use, keep at room temperature (below 30°C) for up to 30 days. Never freeze a pen. If you suspect storage issues, ask your pharmacy for a replacement and ensure you're following storage guidelines carefully going forward.
Is Mounjaro 7.5 the same dose as Wegovy when comparing GLP-1 medications?
Mounjaro and Wegovy are not directly equivalent — Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is a GLP-1 agonist only. The doses work differently. An approximate conversion might be Mounjaro 7.5mg ≈ Wegovy 1–1.7mg, but switching medications requires prescriber guidance. Never switch without clinical oversight.
Can I access a higher Mounjaro dose through NHS weight management services?
NHS tier 3 specialist weight management services can prescribe Mounjaro up to the maximum 15mg dose based on your assessment and response. Availability varies by region and ICB. If you're on the NHS waiting list or already under a specialist service, ask your prescriber about dose escalation at your next review. Private online prescribing also offers the full dose range.
Ready to take control of your weight loss journey?
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