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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What Mounjaro Dosage Is Best for Weight Loss?
The best Mounjaro dosage for weight loss depends on individual factors assessed during a clinical consultation, not a one-size-fits-all answer. Mounjaro starts at 2.5 mg weekly and increases gradually over 16+ weeks, with most people reaching a maintenance dose between 5 mg and 15 mg. Clinical trials showed average weight loss of 15% to 21% of body weight across the full dose range, alongside reduced-calorie diet and increased activity. Your prescriber determines the right dose for you based on your health, tolerance, and response.
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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.
Mounjaro vs Wegovy: Dose Ranges and Trial Data
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly weight loss injections available as a weekly weight loss injection in the UK, but they differ significantly in mechanism and dosing.
Mounjaro dose range: 2.5 mg (starting) to 15 mg (maximum), with typical maintenance at 5–15 mg weekly.
Wegovy dose range: 0.25 mg (starting) to 2.4 mg (maximum), with typical maintenance at 1.7–2.4 mg weekly.
In clinical trials, Mounjaro (SURMOUNT-1) achieved approximately 20.9% average weight loss at the 15 mg dose over 72 weeks. Wegovy (STEP-1) achieved approximately 14.9% average weight loss at 2.4 mg over 68 weeks—both alongside lifestyle changes. Individual results vary significantly. The key difference is mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy activates only the GLP-1 pathway. This dual action may contribute to Mounjaro's slightly larger average weight loss, though both are effective prescription weight loss options.
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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.
Finding Your Right Dose: Prescription and Suitability
Neither Mounjaro nor Wegovy has a universally "best" dosage—the optimal dose is individual. A Mounjaro UK prescription follows a structured dose titration schedule: starting at 2.5 mg, increasing by 2.5 mg every four weeks (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg), based on tolerance and response. Most people find their effective dose within this range and stay there—not everyone needs the maximum 15 mg dose.
Your prescriber assesses suitability based on BMI, weight-related health conditions, other medications, and side effect tolerance. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to understand your starting point. Both medications require clinical assessment—discuss with your GP or licensed prescriber which option suits your individual situation.
- 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.
Does everyone need the maximum 15 mg Mounjaro dose for weight loss?
No. Most people achieve significant weight loss at 5–10 mg. The maximum 15 mg dose is typically reserved for those who need additional support or have reached a plateau. Your prescriber determines the right dose for you based on tolerance and results. Higher doses are not automatically better.
Is Mounjaro more effective than Wegovy for weight loss?
Clinical trials show Mounjaro achieved slightly higher average weight loss (21% vs 15%) at maximum doses, likely due to its dual GIP+GLP-1 mechanism. However, individual results vary considerably. Both are effective prescription medications. Suitability depends on your health profile, not on superiority claims.
How long does it take to reach the right Mounjaro dose?
The standard titration schedule takes 16–20 weeks to reach maximum dose (15 mg), increasing by 2.5 mg every four weeks starting from 2.5 mg. However, many people find their effective dose earlier and remain stable—not everyone titrates to the maximum.
Can I switch from Wegovy to Mounjaro if my dose isn't working?
Dose changes or medication switches are clinical decisions made by your prescriber. Approximate equivalences exist (Wegovy 1.7 mg ≈ Mounjaro 10 mg), but any switch must be managed by a licensed prescriber. Never change medications independently.
What happens if Mounjaro side effects are too strong at my current dose?
Inform your prescriber immediately. Options include staying at your current dose longer before increasing, reducing the dose, or pausing titration. Some side effects ease over time. Your prescriber may adjust the schedule or recommend alternative treatment based on your tolerance and goals.
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.