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 Dose Calculator — Understanding Your Treatment Plan
Mounjaro (tirzepatide) is a prescription-only weight management injection that works through a carefully planned dose escalation schedule. Rather than starting at the full dose, your prescription follows a tiered approach where you begin at 2.5 mg and gradually increase each dose every 4 weeks, depending on how your body responds. This guide explains how Mounjaro dosing works in the UK, what to expect at each stage, and how a prescriber determines the right dose for you. Our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses, whilst our BMI calculator provides context for your starting point.
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.
How Mounjaro Dosing Works — The Titration Schedule
Mounjaro is a dual GIP and GLP-1 receptor agonist that comes as a pre-filled KwikPen with a once-weekly injection. The drug doesn't start at maximum strength — instead, you follow a structured titration schedule designed to help your body adapt and minimise side effects.
- Week 1–4 (Starting dose): 2.5 mg once weekly — allows your system to adjust to the medication
- Week 5–8 (First escalation): 5 mg once weekly — first maintenance dose for many patients
- Week 9–12 (Second escalation): 7.5 mg once weekly — step up if needed
- Week 13–16 (Third escalation): 10 mg once weekly — continued adjustment
- Week 17–20 (Fourth escalation): 12.5 mg once weekly — high-dose tier
- Week 21+ (Maximum dose): 15 mg once weekly — the highest approved dose
Each KwikPen contains exactly 4 weeks' worth of doses. You must spend a minimum of 4 weeks at each dose level before increasing — your prescriber will not escalate faster than this. If you experience severe side effects, your dose can be held or paused.
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.
Which Dose Is Right For You? — Personalised Assessment
Your prescriber will assess which starting and target dose is appropriate based on your individual health, weight loss response, and side effect tolerance. Not everyone needs to reach the maximum 15 mg dose — many patients achieve good results at 5 mg, 10 mg, or 12.5 mg and choose to remain there.
Clinical trial data showed that at 15 mg, patients lost an average of approximately 20.9% of their body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity — but individual results vary significantly. Your prescriber may recommend staying at a lower maintenance dose if you're seeing good progress and tolerating it well. Use our weight loss calculator above to explore projected outcomes at different doses, and remember that reaching the maximum dose is not a goal in itself — finding your optimal dose is.
- 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 happens if I miss a Mounjaro injection?
If you miss a dose and remember within 4 days, take it as soon as you can, then continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next injection on your normal scheduled day. Never double up. Always leave at least 72 hours between doses.
Can I stay on a lower Mounjaro dose permanently?
Yes. You do not need to reach the 15 mg maximum dose. Many patients remain on 5 mg, 7.5 mg, 10 mg, or 12.5 mg long-term if they're seeing good results and managing side effects well. Your prescriber will help you find your optimal maintenance dose.
How long does each Mounjaro KwikPen last?
Each pre-filled KwikPen contains exactly 4 weekly doses, so one pen lasts 4 weeks. You'll need a new pen every month. Your prescriber or pharmacy will arrange repeat supplies — ensure you order before you run out.
What if I experience severe nausea at my current dose?
Contact your prescriber or pharmacist immediately. Options include staying on your current dose longer before escalating, pausing escalation, or in some cases, stepping back down temporarily. Do not stop injecting without guidance — your prescriber can adjust your plan.
Is Mounjaro the same as Wegovy or Ozempic?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. Wegovy (semaglutide) is a GLP-1 agonist only — a different medication with different dosing. Ozempic is also semaglutide but approved for diabetes, not weight loss in the UK. Each has a unique titration schedule. Your prescriber will recommend which is appropriate for you.
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.