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 Should I Increase Your Mounjaro Dose?
Your Mounjaro dose increase is managed carefully by your prescriber following a structured titration schedule. In the UK, Mounjaro (tirzepatide) is prescribed starting at 2.5 mg and escalated gradually every 4 weeks if tolerated well. You should never increase your dose yourself — your prescriber decides when you're ready to move to the next dose based on how your body is responding, your weight loss progress, and any side effects you're experiencing. This measured approach helps minimise side effects whilst maximising effectiveness.
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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 Titration Schedule — What to Expect
The standard UK Mounjaro dose escalation follows this timeline:
- 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 (if tolerated)
- Weeks 13–16: 10 mg once weekly (if appropriate)
- Weeks 17–20: 12.5 mg once weekly (optional)
- Week 21+: 15 mg once weekly (maximum dose)
Each dose step requires a minimum of 4 weeks before increasing further. Your prescriber will assess your tolerance, weight loss response, and any side effects before recommending escalation. Not everyone reaches the maximum dose — many people achieve their weight loss goals at lower doses like 5 mg or 10 mg. Your KwikPen will contain 4 weeks' supply at your current dose.
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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.
Reasons Your Prescriber Might Delay or Pause Dose Increases
Your prescriber may recommend staying longer at your current dose or pausing escalation if you're experiencing significant side effects like persistent nausea, vomiting, or gastrointestinal symptoms. If you're already losing weight consistently at your current dose, escalation may not be necessary — clinical trials showed that meaningful weight loss occurs at multiple dose levels, and individual results vary. Some people also find that side effects decrease naturally over 2–4 weeks at each dose, making it easier to tolerate the next step. Always discuss any concerns with your prescriber before your next scheduled increase date.
- 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 increase my Mounjaro dose faster than every 4 weeks?
No — the 4-week minimum between doses is designed into the prescribing protocol for safety. Increasing too quickly increases nausea, vomiting, and other side effects without improving results. Your prescriber will not escalate before 4 weeks have passed, even if you request it.
What if I'm not losing weight at my current Mounjaro dose?
Weight loss typically becomes more noticeable weeks 8–12 into treatment. If you're not seeing results by week 12 at a particular dose, discuss this with your prescriber — they may recommend escalating to the next dose, or exploring whether diet and activity levels need adjustment. Clinical trials showed dose-dependent results, so higher doses may help, but this is an individual decision.
What's the difference between Mounjaro and Wegovy dose schedules?
Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg, whilst Wegovy (semaglutide) starts at 0.25 mg and escalates to 2.4 mg. Both use 4-week intervals between doses. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is a GLP-1 agonist only — they have different mechanisms and are not directly interchangeable.
Can I stay on a lower Mounjaro dose permanently?
Yes — many people achieve their weight loss goal at doses like 5 mg, 7.5 mg, or 10 mg and remain on that dose long-term. Your prescriber will help you find your optimal dose — the one that gives you effective weight loss with side effects you can tolerate. Reaching the maximum 15 mg dose is not necessary for everyone.
What happens if I have severe side effects when I increase my Mounjaro dose?
Contact your prescriber immediately. They may recommend staying at your current dose longer, reducing back to your previous dose, or stopping treatment. Severe side effects like persistent vomiting, severe abdominal pain, or signs of pancreatitis (pain radiating to the back) require urgent medical attention and should be reported to your GP or 111.
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.