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 — Complete UK Titration Guide
Mounjaro is prescribed as a once-weekly injection that starts at 2.5 mg and increases gradually over weeks, with a maximum dose of 15 mg. Understanding the dosing schedule, how titration works, and how Mounjaro compares to Wegovy (another weight loss injection) can help you understand what to expect if prescribed. Both are prescription-only medications requiring a clinical assessment from a UK-licensed prescriber.
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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 Dosing Schedule & How It Works
Mounjaro starts at 2.5 mg once weekly for the first four weeks, then increases by 2.5 mg every four weeks until an effective dose is reached or the maximum of 15 mg is reached. Each KwikPen contains four pre-filled doses (a month's supply) at the same strength.
- Weeks 1–4: 2.5 mg weekly (starting/adjustment dose)
- Weeks 5–8: 5 mg weekly
- Weeks 9–12: 7.5 mg weekly
- Weeks 13–16: 10 mg weekly
- Weeks 17–20: 12.5 mg weekly
- Week 21+: 15 mg weekly (maintenance/maximum)
Your prescriber may adjust your pace based on side effects or tolerance. Clinical trials (the SURMOUNT studies) showed average weight loss of approximately 15–21% of body weight, though individual results vary significantly. Use our free GLP-1 weight loss calculator to see potential projections at different doses.
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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.
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Mounjaro vs Wegovy — Dose Comparison
Mounjaro and Wegovy both inject once weekly but use different mechanisms and dosing scales. Mounjaro uses a dual GIP and GLP-1 receptor agonist (tirzepatide), while Wegovy is a GLP-1-only agonist (semaglutide). Mounjaro's doses range from 2.5 mg to 15 mg; Wegovy ranges from 0.25 mg to 2.4 mg. Approximate dose equivalence suggests Mounjaro 5 mg ≈ Wegovy 0.5 mg, Mounjaro 10 mg ≈ Wegovy 1.7 mg, and Mounjaro 15 mg ≈ Wegovy 2.4 mg — though any switch between medications must be guided by your prescriber. In SURMOUNT trials, Mounjaro showed average weight loss of 15–21%; STEP trials with Wegovy showed approximately 15% average loss. Both require a UK prescription and clinical assessment to determine suitability.
- 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 is the starting dose of Mounjaro in the UK?
The starting dose of Mounjaro in the UK is 2.5 mg injected once weekly. This is the adjustment dose used for the first four weeks to allow your body to adapt. After four weeks, the dose typically increases to 5 mg and continues escalating by 2.5 mg every four weeks until an effective dose is reached or the maximum of 15 mg is achieved.
How long does it take to reach the maximum Mounjaro dose?
It typically takes 20 weeks (approximately five months) to reach the maximum dose of 15 mg, as each dose level is held for four weeks minimum before escalating. Your prescriber may adjust this timeline based on how well you tolerate each dose and any side effects you experience. Some people stay on lower maintenance doses if they achieve their goals earlier.
Is Mounjaro or Wegovy the better choice for weight loss?
Neither is objectively "better" — suitability depends on your individual health profile, medical history, and prescriber assessment. Mounjaro (tirzepatide) uses a dual mechanism; Wegovy (semaglutide) uses a single GLP-1 mechanism. Clinical trial data shows similar average weight loss (15–21% for Mounjaro, ~15% for Wegovy), but results vary between individuals. Your GP or prescriber will recommend the most appropriate option for you.
Can I adjust my Mounjaro dose myself or skip doses?
No — Mounjaro dosing must be managed by your prescriber. You should not adjust, skip, or increase doses without guidance. If you miss a dose within four days of when it was due, take it as soon as remembered and continue your normal schedule. If more than four days have passed, skip that dose and take your next injection on the normal scheduled day.
Will I stay on the maximum 15 mg dose of Mounjaro forever?
Not necessarily. Once you reach an effective dose that gives you desired results, you may stay at that level indefinitely while it remains suitable and well-tolerated. Some people maintain results on 10 mg or 12.5 mg rather than the maximum. Your prescriber will review your progress regularly and adjust as needed. Weight loss maintenance typically requires ongoing treatment — stopping Mounjaro may lead to weight regain over time.
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.