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
When Do You Go Up A Dose On Mounjaro?
Mounjaro (tirzepatide) uses a gradual dose escalation schedule to help your body adjust to the medication. You typically go up a dose every 4 weeks, starting at 2.5 mg and increasing up to a maximum of 15 mg once weekly. Your prescriber will assess your response and tolerability before each increase, and you should stay on each dose for at least 4 weeks before escalating. This measured approach helps minimise side effects whilst optimising weight loss results. Individual timing may vary based on how well you tolerate the medication.
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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 Dose Schedule — Week By Week
Mounjaro follows a structured 20-week escalation pathway, though your prescriber may adjust timing based on your individual response. Here's the standard schedule:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly (first escalation)
- 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)
Each KwikPen contains 4 doses (one month's supply). You must wait at least 4 weeks on each dose before increasing. Your prescriber may pause escalation, repeat a dose, or progress more slowly if you're experiencing side effects or need time to adjust. The goal is finding your optimal dose — higher doses aren't automatically better if tolerability is an issue.
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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.
Why The Gradual Escalation Approach?
Slow dose escalation helps your body adapt to tirzepatide and reduces the likelihood of severe nausea, vomiting, or gastrointestinal discomfort. Clinical data shows that spreading doses over 20 weeks improves tolerability and adherence compared to rapid escalation. Your prescriber may recommend staying longer on a particular dose if you experience side effects or if your weight loss is progressing well — there's no requirement to reach 15 mg. Many people achieve their health goals at 10 mg or 12.5 mg. Use our GLP-1 weight loss calculator above to estimate potential results at different doses, and remember to log your progress with our free progress tracker to monitor how each dose affects you.
- 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.
Can I skip doses or stay on the same dose longer?
Yes. You must stay on each dose for a minimum of 4 weeks, but you can remain on the same dose longer if you wish or if your prescriber recommends it. Some people find their target dose before reaching 15 mg and choose to stay there. Always follow your prescriber's guidance.
What if I experience severe side effects — do I have to increase?
No. If you're experiencing side effects, your prescriber may pause escalation, repeat the same dose for longer, or reduce to a previous dose. Managing tolerability is important. Contact your prescriber if side effects are affecting your quality of life — dose adjustments can be made.
How quickly do you lose weight on each Mounjaro dose?
Weight loss varies between individuals. Clinical trials showed progressive weight loss throughout the escalation period, with greater average loss at higher doses. Most weight loss occurs in the first 8–12 weeks, though results continue throughout treatment. Our GLP-1 weight loss calculator can help you estimate potential outcomes.
Is there a difference between Mounjaro and Wegovy dose timing?
Yes. Mounjaro escalates over 20 weeks (2.5 mg to 15 mg), whilst Wegovy escalates over 16 weeks (0.25 mg to 2.4 mg). Both require minimum 4 weeks per dose. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is GLP-1 only — different mechanisms, different dose ranges.
What if I miss a week or forget when I'm due to increase?
If you miss a dose, take it within 4 days and continue your normal schedule. For dose increases, contact your prescriber or pharmacist to confirm your next escalation date. Never double-dose or skip doses to "catch up."
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.