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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Tirzepatide Dosage: A Complete UK Guide
Tirzepatide is available in the UK as Mounjaro, a once-weekly weight loss injection that comes in doses ranging from 2.5mg to 15mg. If you've been prescribed tirzepatide or are considering it, understanding the dosage schedule is essential. This guide explains how tirzepatide dosing works, what each dose level means, and what to expect as your dose may increase over time. Use our free GLP-1 weight loss calculator to see how different tirzepatide doses performed in clinical trials.
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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.
How Tirzepatide Dosage Works
Tirzepatide (Mounjaro) is a dual GIP receptor and GLP-1 receptor agonist — meaning it activates two separate appetite-regulation pathways in the body. Dosing begins low and increases gradually over weeks to help your body adjust and minimise side effects. Your prescriber will assess your individual response and tolerability at each dose level before escalating. Each dose is injected once weekly using a pre-filled KwikPen device. The standard escalation schedule involves spending at least 4 weeks at each dose before increasing, though your GP or prescriber may adjust this based on your individual needs and response.
- Week 1–4: 2.5mg — starting/adjustment dose
- Week 5–8: 5mg — first maintenance dose
- Week 9–12: 7.5mg — escalation if needed
- Week 13–16: 10mg — escalation if needed
- Week 17–20: 12.5mg — escalation if needed
- Week 21+: 15mg — maximum dose
Not everyone escalates to the maximum dose — many people achieve their weight loss goals at 5mg, 7.5mg, or 10mg. Your prescriber will personalise your dosing based on your response, tolerability, and health goals.
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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 at Different Tirzepatide Doses
Clinical trial data (SURMOUNT-1) showed that tirzepatide helped participants lose significant weight at each dose level. At 5mg, average weight loss was approximately 15% of body weight over 72 weeks; at 10mg, approximately 19.5%; and at 15mg, approximately 20.9%. Individual results vary considerably — some people lose more, others less — and weight loss is always achieved alongside a reduced-calorie diet and increased physical activity. Your own experience depends on factors including starting weight, genetics, adherence to lifestyle changes, and how your body responds to the medication. Use our BMI calculator and progress tracker to monitor your individual progress from your starting point.
- 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 tirzepatide in the UK?
The starting dose is 2.5mg, injected once weekly using a KwikPen pen. You remain on this dose for 4 weeks to allow your body to adjust. After 4 weeks, your prescriber will assess your response and may escalate to 5mg if appropriate.
Can I skip doses or miss a tirzepatide injection?
If you miss a dose within 4 days, take it as soon as you remember and continue your normal schedule. If more than 4 days have passed, skip that dose and take your next scheduled dose on the normal day. Never double-dose. Always contact your prescriber with concerns.
What is the maximum tirzepatide dose in the UK?
The maximum licensed dose is 15mg once weekly. This is the highest dose used in clinical trials. Not everyone needs to reach this dose — many achieve effective weight loss at lower maintenance doses like 5mg or 10mg.
How long does it take to reach the maximum tirzepatide dose?
Reaching 15mg takes a minimum of 20 weeks if escalating every 4 weeks without interruption. However, most people spend longer on lower doses, and some stop escalating once they reach an effective dose. Your prescriber will manage your individual escalation timeline.
Does tirzepatide dosage affect how much weight I will lose?
Higher doses of tirzepatide were associated with greater average weight loss in trials, but individual results vary significantly. Some people achieve satisfactory weight loss at 5mg or 7.5mg, while others continue to 15mg. Your prescriber will find the right dose for your personal goals and tolerability.
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.