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 Am I Not Losing Weight On Mounjaro 7.5 Mg?
It's natural to wonder why you're not seeing weight loss results on a weekly weight loss injection like Mounjaro 7.5 mg. While clinical trials show that Mounjaro may help with significant weight loss, individual results vary considerably — and plateaus, slower-than-expected progress, and non-response do happen. This guide explains the most common reasons why Mounjaro may not be delivering the results you hoped for, and what you can discuss with your prescriber.
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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.
Common Reasons For Slow Or No Weight Loss On Mounjaro 7.5 Mg
Several factors may explain why you're not seeing the weight loss you expected on Mounjaro 7.5 mg:
- Still in early treatment: Most people require at least 4–8 weeks at each dose before reaching a steady state. At 7.5 mg, your body may still be adjusting — weight loss often accelerates after 12 weeks on a stable dose.
- Diet intake higher than needed: Mounjaro reduces appetite and helps you feel fuller, but it doesn't eliminate hunger entirely. If calorie intake remains above your needs, weight loss will plateau. This is the most common reason for slower-than-expected results.
- Insufficient physical activity: Weight loss relies on both reduced calorie intake and increased expenditure. If activity levels are low, results will be slower. The NHS recommends 150 minutes of moderate activity weekly alongside any diet changes.
- Individual variation: Not everyone responds to Mounjaro at the same rate. Genetics, metabolism, hormonal factors, and underlying conditions (like thyroid disease or PCOS) all affect weight loss response.
- Weight loss plateau: This is normal. Your body may lose weight steadily for 8–12 weeks, then plateau for 2–4 weeks before dropping again. This is a sign your body is adjusting, not that Mounjaro has stopped working.
- Hidden calorie sources: Drinks, condiments, cooking oils, and portion sizes are easy to underestimate. Keeping a food diary can reveal where extra calories are hiding.
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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.
What To Do If Mounjaro Isn't Working As Expected
If you've been on Mounjaro 7.5 mg for at least 8–12 weeks and haven't seen meaningful progress, discuss this with your prescriber — they can assess whether dose escalation, dietary adjustments, or other factors might help. Your prescriber may recommend increasing to 10 mg if you're tolerating 7.5 mg well and have no contraindications. Track your weight loss progress consistently using our free progress tracker — weekly weigh-ins can be misleading, but trends over 4-week periods are more reliable. Consider also whether your expectations are realistic: the NHS recommends weight loss of 0.5–1 kg per week as sustainable, which means even on an effective prescription weight loss injection, dramatic results take time. If you have underlying conditions like thyroid disease, diabetes medication changes, or hormonal issues, these may also affect results and should be discussed with your GP.
- 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 Mounjaro 7.5 mg take to show weight loss results?
Most people see initial weight loss within 4–8 weeks at a stable dose, though individual timescales vary. At 7.5 mg specifically, your body may still be adjusting if you've recently escalated from 5 mg. Give it at least 8–12 weeks at the same dose before concluding it isn't working. Use our GLP-1 weight loss calculator to set realistic expectations for your dose.
Should I increase to Mounjaro 10 mg if 7.5 mg isn't working?
Don't increase the dose without discussing it with your prescriber first. They'll assess whether 8+ weeks of treatment has been given, check your adherence and diet, and consider whether escalation is appropriate. Increasing too quickly without addressing dietary habits often leads to disappointment.
Is there a difference between Mounjaro and Wegovy for weight loss?
Both are prescription weight loss injections, but Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss in clinical trials (~20.9% vs ~14.9%), but individual response varies. Your prescriber will advise which is suitable for you.
Could my diet be sabotaging weight loss on Mounjaro?
Yes — this is the single most common reason for disappointing results. Mounjaro suppresses appetite but doesn't prevent overeating. Track your intake honestly for a week; you may find calorie intake is higher than expected. Aim for a sustainable deficit of 500 kcal daily for approximately 0.5 kg weekly loss.
What if Mounjaro works initially then stops — is this normal?
Weight loss plateaus are completely normal and not a sign Mounjaro has stopped working. Your body adjusts to changes, causing temporary plateaus of 2–4 weeks. Continue consistent diet and activity — progress often resumes. If a plateau lasts 8+ weeks with no change, discuss with your prescriber about dose escalation or investigating underlying causes.
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.