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 Dosage: Complete UK Guide
Mounjaro (tirzepatide) is available in doses ranging from 2.5 mg to 15 mg, administered as a once-weekly injection. Each dose comes pre-filled in a KwikPen device. The dosage you receive depends on your individual health needs and how your body responds to treatment. Your prescriber will start you on a lower dose and gradually increase it over time if needed. This article explains how Mounjaro dosing works in the UK, the typical titration schedule, and what to expect at each dose level.
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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 Dose Range and Titration Schedule
Mounjaro comes in five main doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. You start on 2.5 mg for the first four weeks, then your prescriber may increase your dose every four weeks if appropriate. Each KwikPen contains four pre-filled injections (a four-week supply). The typical dosing schedule works like this:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly (first escalation)
- Weeks 9–12: 7.5 mg once weekly (optional increase)
- Weeks 13–16: 10 mg once weekly (optional increase)
- Weeks 17–20: 12.5 mg once weekly (optional increase)
- Week 21+: 15 mg once weekly (maximum dose)
You must stay on each dose for at least four weeks before increasing. Not everyone needs to reach the maximum dose — your prescriber will find the right dose for you based on your response and how you tolerate the medication.
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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.
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What Happens at Each Dose Level
At lower doses (2.5–5 mg), you may experience appetite suppression and modest changes in how full you feel after eating. As your dose increases to 7.5–10 mg, these effects typically become more pronounced. Higher doses (12.5–15 mg) are associated with greater weight loss in clinical trials, though individual results vary significantly. Clinical trial data showed that at 15 mg, participants lost an average of approximately 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, higher doses also increase the likelihood of gastrointestinal side effects such as nausea and constipation. Your prescriber will work with you to find the optimal dose — one that balances effectiveness with tolerability for your 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.
What is the starting dose of Mounjaro?
The starting dose is 2.5 mg, injected once weekly. You remain on this dose for four weeks before any increase. This allows your body to adjust and helps your prescriber monitor how you respond before escalating.
How quickly does Mounjaro increase in dose?
Doses increase every four weeks if your prescriber decides escalation is appropriate. You move from 2.5 mg to 5 mg after four weeks, then to 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg. There is a minimum of four weeks between each step.
What is the maximum dose of Mounjaro?
The maximum recommended dose is 15 mg once weekly. This is the highest dose available. Not all patients need to reach the maximum — your prescriber will determine the most suitable dose for your individual health needs and response.
Can I skip dose increases or stay on a lower dose?
Yes, absolutely. Your prescriber may decide to keep you on a lower dose if you are experiencing good results, tolerating it well, or if side effects are a concern. Dose management is personalised — there is no one-size-fits-all approach.
How do I know which dose of Mounjaro I should be on?
Your prescriber assesses your individual circumstances, including your weight, health conditions, response to treatment, and any side effects you experience. Use our free GLP-1 weight loss calculator to see projected outcomes at different doses, then discuss your specific situation with your prescriber for personalised guidance.
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.