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 Dose for Weight Loss: How It Works
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection available in the UK through clinical assessment. Unlike some alternatives, Mounjaro uses a dual GIP and GLP-1 mechanism that may support appetite regulation and weight management. Doses range from 2.5 mg to 15 mg, increasing gradually over weeks. Understanding how Mounjaro dosing works, and how it compares to other prescription weight loss injections like Wegovy, helps you have an informed conversation with your prescriber about which option might suit your health needs.
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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.
Mounjaro vs Wegovy: Dose Titration and Trial Results
Mounjaro dose escalation: starts at 2.5 mg once weekly, increasing every 4 weeks through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to a maximum of 15 mg. Each KwikPen contains 4 weekly doses.
In the SURMOUNT-1 clinical trial, participants on Mounjaro 15 mg lost an average of 20.9% of body weight over 72 weeks alongside reduced-calorie diet and increased physical activity. By comparison, Wegovy (semaglutide), a GLP-1-only injection, achieved approximately 14.9% average weight loss in the STEP-1 trial at its maximum 2.4 mg dose.
The key difference: Mounjaro activates two hormone pathways (GIP and GLP-1), while Wegovy activates GLP-1 only. This dual mechanism may explain the difference in clinical trial outcomes, though individual results vary significantly. Clinical trial data shows results when combined with lifestyle changes—neither medication works alone.
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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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Which Dose Is Right for You? Prescriber Assessment
Your prescriber will assess your individual health, BMI, weight-related conditions, and medical history to determine the starting dose (usually 2.5 mg) and appropriate escalation schedule. Some people reach therapeutic benefit at lower doses (5–10 mg); others may progress to the maximum 15 mg. Dose choice is not based on how much weight you want to lose—it's based on your health profile and how your body responds.
Use our free GLP-1 weight loss calculator to estimate potential weight loss ranges at different doses, and our BMI calculator to understand your current health status. Both tools provide context for discussions with your prescriber. Remember, prescriptions are issued following clinical assessment, and neither Mounjaro nor Wegovy is suitable for everyone.
- 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.
What's the starting dose of Mounjaro for weight loss?
Mounjaro starts at 2.5 mg once weekly for the first 4 weeks. This is a starter dose to help your body adjust. After 4 weeks, your prescriber will increase the dose if appropriate. The gradual escalation (titration) reduces side effects and allows your prescriber to find the dose that works best for your health.
How long does it take to reach the maximum Mounjaro dose?
It typically takes 20–24 weeks to reach the maximum 15 mg dose, as each dose increase requires a minimum of 4 weeks. However, not everyone reaches 15 mg—many people achieve good results at lower doses like 5 mg or 10 mg. Your prescriber will guide your individual titration schedule.
Does a higher Mounjaro dose assures more weight loss?
No. Clinical trials show a dose-response relationship—higher doses were associated with greater average weight loss—but individual results vary. Some people lose significant weight at 5 mg; others need higher doses. Your prescriber determines your dose based on your health, not on a target weight loss amount.
How does Mounjaro compare to Wegovy for weight loss?
In clinical trials, Mounjaro (tirzepatide) showed higher average weight loss (20.9% at 15 mg) than Wegovy (semaglutide) (14.9% at 2.4 mg). Mounjaro uses a dual GIP+GLP-1 mechanism; Wegovy is GLP-1 only. Both are prescription-only and require clinical assessment. Your prescriber will recommend the most suitable option for your individual circumstances.
Can I switch between Mounjaro and Wegovy if one doesn't work?
Switching between medications is a prescriber decision and must be managed carefully—there is no official established dose conversion between them. If one medication isn't suitable after a fair trial period, your prescriber may recommend switching. Any change requires a new clinical assessment and consultation with your prescriber.
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.