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 Injection Dose — Complete UK Guide
Mounjaro (tirzepatide) is a prescription-only weight management injection that works through a gradual dose escalation schedule. In the UK, treatment starts at 2.5mg once weekly and increases over several months to a maximum of 15mg weekly. The stepped approach allows your body to adjust while helping minimise side effects. This guide explains how Mounjaro doses work, the typical titration timeline, and what each dose stage involves. Always follow your prescriber's guidance — individual dose progression depends on your tolerance and response.
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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 Doses Progress in the UK
Mounjaro treatment follows a structured dose titration schedule designed to help your body adjust gradually. You start at the lowest dose and increase every 4 weeks if tolerated well. Here's the standard UK escalation pathway:
- Weeks 1–4: 2.5mg once weekly (starting dose)
- Weeks 5–8: 5mg once weekly (first maintenance dose)
- Weeks 9–12: 7.5mg once weekly (escalation)
- Weeks 13–16: 10mg once weekly (escalation)
- Weeks 17–20: 12.5mg once weekly (escalation)
- Week 21+: 15mg once weekly (maximum dose)
Each Mounjaro KwikPen contains four pre-filled doses for one month's treatment. Your prescriber may adjust timing based on your response. Many people see meaningful results at 5mg or 10mg and may not need to progress to the maximum dose. The dose titration approach differs from weekly weight loss injections like Wegovy, which also escalates but over a different timeframe.
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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 to Expect at Each Dose Stage
Starting at 2.5mg helps your body adapt to Mounjaro's dual GIP and GLP-1 mechanism. Side effects like nausea are typically mild at lower doses and often settle within a few days. By week 5, most people move to 5mg — the first maintenance dose where many experience noticeable appetite reduction. Clinical trials showed that 5mg produces approximately clinically studied weight loss on average, whilst 10mg and 15mg produce greater results, though individual outcomes vary. Your prescriber will assess your progress every 4 weeks and may pause escalation if you're experiencing significant side effects or achieving your goals at a lower dose. Using our free GLP-1 weight loss calculator can help you understand potential outcomes at different dose levels alongside your healthy lifestyle changes.
- 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 is 2.5mg once weekly. This is the lowest dose designed to help your body adjust to the medication. After 4 weeks, if tolerated well, your prescriber typically increases you to 5mg weekly. Starting low helps minimise side effects like nausea.
How long does Mounjaro dose titration take?
Full dose titration takes approximately 20–24 weeks if you progress through all escalation stages (2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg). However, many people achieve their goals at lower doses and may not need the maximum. Your prescriber adjusts based on your individual response.
What is the maximum Mounjaro dose?
The maximum dose is 15mg once weekly. This is the highest approved dose in the UK. Not everyone needs to reach the maximum — clinical trials showed significant weight loss at 5mg and 10mg. Your prescriber will determine the right dose for you.
Can I skip dose increases or stay on a lower dose?
Yes. If you're achieving good results at 5mg or 10mg, or if side effects are significant, your prescriber may recommend staying at that dose rather than escalating further. Dose progression is individualised based on your tolerance and goals.
How does Mounjaro dosing compare to Wegovy?
Both are once-weekly injections but follow different escalation schedules. Mounjaro starts at 2.5mg and reaches 15mg maximum. Wegovy starts at 0.25mg and reaches 2.4mg maximum. Mounjaro is a dual GIP+GLP-1 agonist, whilst Wegovy is GLP-1 only. Your prescriber will recommend based on your individual needs.
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.