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
How Often Is Mounjaro Taken?
Mounjaro (tirzepatide) is taken as a once-weekly injection, making it a convenient option for UK adults managing weight. The dose starts at 2.5 mg and gradually increases every 4 weeks up to a maximum of 15 mg. This structured approach, called dose titration, allows your body to adjust while your prescriber monitors your response. Understanding the dosing schedule helps you plan your weight management journey alongside dietary changes and increased activity. Our GLP-1 weight loss calculator can help you explore potential outcomes with different doses.
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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.
Mounjaro Dosing Schedule vs Wegovy
Mounjaro (tirzepatide) follows a specific dose titration schedule over approximately 20 weeks to reach maximum dose. You inject once weekly at the same day each week, using a pre-filled KwikPen device:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly
- Weeks 9–12: 7.5 mg once weekly
- Weeks 13–16: 10 mg once weekly
- Weeks 17–20: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum maintenance dose)
Wegovy (semaglutide) also escalates weekly but uses smaller increments starting at 0.25 mg, reaching 2.4 mg maximum by week 17. Both are once-weekly injections, but Mounjaro's dual GIP and GLP-1 mechanism means clinical trial data showed different average weight loss outcomes—Mounjaro trials demonstrated approximately 15–clinically studied weight loss versus Wegovy's approximately 15% in comparative studies. Your prescriber will determine which suits you after clinical assessment.
Clinically BackedWeight Loss
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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.
When to Escalate Your Dose
Your prescriber will increase your Mounjaro dose only after you have been on the current dose for a full 4 weeks. This allows time to assess how well you tolerate it and how your weight responds. If you experience significant side effects, your prescriber may delay escalation or keep you at your current dose longer. You do not skip doses or double up—you inject once every 7 days at the same time, using a new KwikPen each week. Missing a dose? If within 4 days, inject as soon as you remember; if more than 4 days have passed, skip that dose and continue your normal schedule. Track your progress with our free progress tracker to share updates with your prescriber at review appointments.
- 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.
How many times per week do I inject Mounjaro?
Mounjaro is a once-weekly injection. You inject on the same day each week using a pre-filled KwikPen device. You do not inject multiple times per week—just one dose of your current dose strength every 7 days.
How long does it take to reach the maximum Mounjaro dose?
It takes approximately 20 weeks to reach the maximum dose of 15 mg. Your dose increases every 4 weeks, starting at 2.5 mg. Your prescriber may adjust this timeline based on your tolerance and response. Some people maintain a lower dose if it works well for them.
Can I stay on a lower Mounjaro dose instead of escalating to 15 mg?
Yes. If you experience good weight loss and tolerate a lower dose well, your prescriber may recommend staying at that dose rather than escalating further. The goal is effective, sustainable weight management with tolerable side effects—not necessarily reaching the maximum dose.
What happens if I miss a Mounjaro injection?
If you miss your weekly injection, take it within 4 days of the missed dose and continue your normal schedule the following week. If more than 4 days have passed, skip that dose and resume your regular injection day. Never take a double dose to make up for a missed one.
Is Mounjaro taken more or less frequently than Wegovy?
Both Mounjaro and Wegovy are once-weekly injections, so the injection frequency is the same. However, Mounjaro reaches maximum dose over a longer period (20 weeks) with larger dose increments, while Wegovy escalates more gradually with smaller steps. Your UK prescriber will explain which schedule suits your 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.