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 Doses — Complete UK Dosing Guide
Mounjaro (tirzepatide) is available in five therapeutic doses in the UK, starting from 2.5 mg and escalating to a maximum of 15 mg once weekly. Each dose is administered as a single injection using a pre-filled KwikPen device. Your prescriber will recommend a starting dose and then gradually increase it over several weeks based on your response and tolerance. Understanding how Mounjaro dosing works will help you know what to expect throughout your treatment journey.
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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.
How Mounjaro Dosing Works in the UK
Mounjaro is supplied in five standard doses, each given as a once-weekly injection. The standard dosing schedule works as follows: 2.5 mg for weeks 1–4 (starting dose), 5 mg for weeks 5–8, 7.5 mg for weeks 9–12, 10 mg for weeks 13–16, 12.5 mg for weeks 17–20, and finally 15 mg from week 21 onwards (maximum dose). Each KwikPen contains exactly four weekly doses. Your prescriber may adjust this schedule based on your individual response, tolerability of side effects, and weight loss progress. You should remain on each dose for at least 4 weeks before increasing to the next level. If you experience significant side effects, your prescriber may delay escalation or keep you on your current dose longer. Clinical trials showed that weight loss accumulates gradually—results are not immediate, and most improvement occurs over several months.
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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.
Expected Weight Loss by Dose
The SURMOUNT-1 clinical trial data shows average weight loss outcomes at different doses over 72 weeks: at 5 mg, participants lost approximately 15% of their body weight; at 10 mg, approximately 19.5%; and at 15 mg (maximum), approximately 20.9%. These results were achieved alongside a reduced-calorie diet and increased physical activity. Individual results vary considerably—some people achieve significant weight loss at lower doses, whilst others require higher doses to see meaningful results. Your personal outcome depends on factors including your starting weight, metabolism, adherence to lifestyle changes, and how your body responds to the medication. Try our GLP-1 weight loss calculator to estimate potential weight loss at different Mounjaro doses based on your current weight. Always discuss realistic expectations with your prescriber during your clinical assessment.
- 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 quickly does Mounjaro work at different doses?
Mounjaro is not a gradual weight management medication. You typically see early appetite suppression within days of starting, but meaningful weight loss usually appears within 4–8 weeks. Weight loss accelerates as you increase through doses, with most improvement occurring between weeks 8 and 20. Individual timelines vary based on lifestyle adherence and metabolism.
Can I stay on a lower Mounjaro dose instead of increasing?
Yes. If you're achieving your weight loss goals and tolerating your current dose well, your prescriber may recommend staying at that dose rather than escalating further. There's no requirement to reach the maximum dose—treatment is personalised based on your individual response and health outcomes.
What if I miss a Mounjaro dose?
If you miss a dose within 4 days of when you should have taken it, inject as soon as you remember and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and inject on your normal scheduled day. Never take a double dose, and ensure at least 72 hours (3 days) between injections.
Is Mounjaro prescription-only in the UK?
Yes, Mounjaro (tirzepatide) is a prescription-only medicine in the UK. You'll need a clinical assessment from a UK-licensed prescriber before it can be prescribed. This may be through NHS specialist weight management services or via a private online consultation with a registered healthcare provider.
How do Mounjaro doses compare to Wegovy doses?
Mounjaro and Wegovy (semaglutide) use different dosing systems. Mounjaro escalates from 2.5 mg to 15 mg once weekly, whilst Wegovy escalates from 0.25 mg to 2.4 mg. The medications work differently—Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is a GLP-1 agonist only—so direct dose comparisons aren't straightforward.
Ready to take control of your weight loss journey?
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