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
Free tracker included with every download this week
Mounjaro Dosage: NHS & UK Prescribing Information
Mounjaro (tirzepatide) is a prescription-only, once-weekly injection licensed in the UK for weight management in adults. The dosage starts at 2.5 mg and can be increased gradually up to a maximum of 15 mg per week, depending on individual tolerance and clinical response. In the UK, Mounjaro is subject to MHRA additional monitoring (Black Triangle status) and is typically prescribed through NHS specialist tier 3 weight management services or by private prescribers following a thorough clinical assessment. Understanding the dosage schedule and how it's tailored to your health profile is essential for safe and effective use.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
NHS Dosage Schedule & Eligibility Criteria
Mounjaro dosage in the UK follows a structured titration schedule to help your body adjust to the medication while minimising side effects. You start at 2.5 mg once weekly for the first 4 weeks, then typically increase to 5 mg weekly for weeks 5–8. From week 9 onwards, your prescriber may escalate further to 7.5 mg, 10 mg, 12.5 mg, or the maximum of 15 mg once weekly, depending on your response and tolerance. Each dose is administered as a single injection using a pre-filled KwikPen device.
NHS eligibility for Mounjaro requires: a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² if you have weight-related health conditions such as type 2 diabetes, prediabetes, hypertension, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds (from 27.5 kg/m²) due to higher health risk at lower weights.
- Minimum 4 weeks on each dose before escalation
- Doses are taken exactly 7 days apart
- If you miss a dose within 4 days, take it as soon as remembered
- If more than 4 days have passed, skip that dose and resume your normal schedule
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 vs Private Route in the UK
NHS access: Mounjaro is prescribed through tier 3 specialist weight management services, typically following referral from your GP. NICE has approved tirzepatide for use within these services, though availability varies significantly by region and NHS integration care board (ICB). Many areas have substantial waiting lists for specialist services, sometimes extending several months.
Private access: You can obtain a Mounjaro prescription privately through a GPhC-registered online prescriber without an NHS referral. This route involves an online clinical assessment and is available more quickly than NHS services in most areas. Use our free GLP-1 weight loss calculator to explore potential outcomes at different Mounjaro doses, and the BMI calculator to assess your personal eligibility criteria before speaking with a prescriber.
- 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 2.5 mg, administered as a once-weekly injection. This lower dose allows your body to adjust and helps minimise nausea and other side effects. After 4 weeks, your prescriber will typically increase you to 5 mg based on your tolerance.
Can you skip a dose of Mounjaro or take it more frequently?
No. Mounjaro must be taken exactly once per week, 7 days apart. If you miss a dose within 4 days, take it as soon as you remember, then resume your normal weekly schedule. Do not take two doses close together.
What is the maximum Mounjaro dose available in the UK?
The maximum approved dose is 15 mg once weekly. Not all patients require or tolerate the maximum dose; your prescriber will adjust based on your clinical response, weight loss progress, and any side effects.
How long does it take to reach the maximum Mounjaro dose?
The standard titration schedule takes approximately 20 weeks (about 5 months) to reach 15 mg, increasing gradually every 4 weeks. This slow escalation helps your body adapt and reduces the risk of gastrointestinal side effects.
Do I need a prescription to get Mounjaro in the UK?
Yes. Mounjaro is prescription-only in the UK and requires a clinical assessment by a licensed prescriber. This can be through NHS specialist services (tier 3) or a private GPhC-registered online prescriber. Your prescriber will assess your eligibility and suitability before issuing a prescription.
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.