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 7.5mg Not Working — What to Know
If Mounjaro at 7.5mg isn't delivering the expected results, you're not alone — individual responses to weight loss injections vary significantly. This guide explains the difference between Mounjaro (tirzepatide) and Wegovy (semaglutide), why some people see better results on one medication over the other, and what options are available through your prescriber. Both are prescription-only medications available in the UK following clinical assessment, and understanding the differences can help you have an informed conversation with your GP or prescriber about next steps.
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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.
Clinical Evidence: Mounjaro vs Wegovy Trial Results
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist tested in the SURMOUNT clinical trials. At 7.5mg (the second maintenance dose), participants lost an average of approximately 15% of their body weight over 72 weeks when combined with a reduced-calorie diet and exercise. At the maximum 15mg dose, average loss reached approximately 21% of body weight.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, tested in the STEP trials. At the maximum 2.4mg dose, average weight loss was approximately 15% of body weight over 68 weeks with the same lifestyle support.
- Mounjaro's dual mechanism (GIP + GLP-1) may theoretically offer greater appetite suppression than GLP-1 alone
- However, trial averages mask individual variation — some people respond better to one mechanism than the other
- 7.5mg is an intermediate dose; your prescriber may increase to 10mg, 12.5mg, or 15mg if appropriate
Neither medication assures weight loss, and real-world results depend on adherence, diet quality, physical activity, and individual metabolism.
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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
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When Mounjaro Isn't Working: Prescriber Discussion Points
If you've been on Mounjaro 7.5mg for at least 4 weeks with minimal results, discuss these factors with your prescriber: dose escalation (the next step is usually 10mg), whether gastrointestinal side effects are limiting your food intake, medication adherence, diet consistency, and physical activity levels.
Some people naturally respond better to different medication mechanisms. Your prescriber may recommend continuing dose titration, switching to Wegovy as a GLP-1-only alternative, or assessing whether other health factors are affecting weight loss (thyroid function, medication interactions, sleep quality, or stress). Using a tool like our GLP-1 weight loss calculator can help you understand projected outcomes at different doses based on clinical trial data, informing your discussion with your healthcare team.
- 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.
Is Mounjaro 7.5mg an effective dose?
Yes, 7.5mg showed an average clinically studied weight loss in clinical trials — however, it's an intermediate dose. Many prescribers continue titration to 10mg, 12.5mg, or 15mg for greater effect. Individual results vary significantly. Discuss dose escalation with your prescriber if you've been on 7.5mg for 4+ weeks.
How does Mounjaro's dual mechanism compare to Wegovy's single GLP-1 action?
Mounjaro activates both GIP and GLP-1 pathways, while Wegovy activates GLP-1 only. Theoretically, dual action may enhance appetite control, but clinical trial results show similar average weight loss (~15% at moderate doses). Some individuals respond better to one mechanism than the other — this is individual variation, not medication failure.
What if I want to switch from Mounjaro to Wegovy?
This is a prescriber decision. Wegovy is an alternative GLP-1 medication available as a UK prescription through NHS specialist services or private prescribing. An approximate equivalent to Mounjaro 7.5mg is Wegovy 1.7mg, though there's no official conversion chart. Your prescriber will assess suitability and manage any switch safely.
How long should I stay on Mounjaro 7.5mg before considering it "not working"?
Most prescribers recommend at least 4 weeks at each dose to assess effectiveness, as the body continues to adjust. If you've been at 7.5mg for 4+ weeks with minimal weight change despite consistent diet and exercise, discuss dose escalation or alternatives with your prescriber — don't assume the medication has failed.
Are there other reasons Mounjaro might not be showing results?
Yes. Weight loss depends on calorie deficit, diet adherence, exercise, sleep quality, stress, and medical factors (thyroid function, insulin resistance, PCOS). Gastrointestinal side effects sometimes limit food intake initially, which can plateau as the body adapts. Your prescriber can assess these factors holistically.
Ready to take control of your weight loss journey?
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