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 Dosing — Complete UK Guide
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK through NHS specialist services and private prescribing. Understanding the dosing schedule is important if you're considering this treatment. This guide explains how Mounjaro dosing works, the dose titration process, and what to expect at each stage. We'll cover NHS access, eligibility criteria, and how Mounjaro compares to other options like Wegovy. Use our free BMI calculator above to check your current weight category and understand whether you may be eligible for prescription weight loss treatment.
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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 administered as a once-weekly injection using a pre-filled KwikPen device. The dosing schedule follows a structured dose titration process, with patients starting at a low dose and gradually increasing every 4 weeks if tolerated:
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first increase)
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum maintenance dose)
Each dose is taken once per week on the same day. A single KwikPen contains four pre-filled pens (one month's supply). Your prescriber may adjust the pace of increases based on side effects or individual response. The gradual titration helps your body adjust to the medication and reduces nausea and stomach-related side effects that are common at higher doses.
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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.
NHS Access and UK Eligibility for Mounjaro
In the UK, Mounjaro is available through NHS specialist weight management services (tier 3 or tier 4) following referral from your GP. NICE has approved tirzepatide for use within the NHS, though availability varies significantly by region and local Integrated Care Board (ICB) funding decisions. To be eligible for NHS Mounjaro, you typically need a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. NHS waiting lists can be lengthy — some regions have waits of 12+ months for specialist services. Private prescribing through online consultations offers faster access, though at individual cost. Try our GLP-1 weight loss calculator to estimate potential outcomes with Mounjaro at different doses.
- 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's the difference between Mounjaro and Wegovy dosing?
Mounjaro (tirzepatide) and Wegovy (semaglutide) use different dosing schedules. Mounjaro starts at 2.5 mg and increases to a maximum of 15 mg weekly. Wegovy starts at 0.25 mg and reaches a maximum of 2.4 mg weekly. Mounjaro has a dual GIP/GLP-1 mechanism, while Wegovy is a GLP-1-only medication. Both require 4-week intervals between dose increases, and both are prescription-only in the UK.
Can I stay on a lower Mounjaro dose if side effects are severe?
Yes. Your prescriber can pause dose increases or maintain you on a lower dose if you're experiencing significant side effects. The goal is to find the lowest effective dose that you tolerate well. Some patients reach good results on 5–7.5 mg rather than the maximum 15 mg. Always discuss side effects with your prescriber before missing a dose.
How long does each KwikPen last?
Each KwikPen contains four pre-filled doses, so one pen lasts four weeks (one month). You'll receive a new pen every four weeks. Store unopened pens in the fridge at 2–8°C. Once started, a pen can be kept at room temperature for up to 30 days, then must be disposed of safely.
Is Mounjaro available on the NHS in all UK regions?
No. NHS availability depends on your local ICB funding decisions and specialist service capacity. Some regions have approved Mounjaro for NHS use; others have restricted access or long waiting lists. Ask your GP whether your local NHS weight management service offers tirzepatide, or discuss private prescribing options if NHS access is delayed.
What happens if I miss a weekly Mounjaro injection?
If you miss a dose within 4 days of your scheduled injection, take it as soon as you remember and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next dose on the originally scheduled day. Never take a double dose. Always maintain at least 72 hours between injections.
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.