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
Why Do You Increase Mounjaro Dose?
Mounjaro doses are increased gradually over several weeks because your body needs time to adjust to the medication. Starting at a low dose and slowly escalating helps your prescriber find the most effective dose for you whilst minimising side effects. This gradual approach, called dose titration, is standard NHS practice and follows the tirzepatide protocol used in clinical trials. Your GP or specialist will monitor your response at each dose level before moving to the next step.
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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.
How Mounjaro Dose Titration Works in the UK
Dose titration is the process of gradually increasing your Mounjaro dose over approximately 20 weeks. Each dose step lasts a minimum of 4 weeks, allowing your body to adapt and your prescriber to assess how well the medication is working for you.
- Weeks 1–4: 2.5 mg — starting dose to assess tolerance
- Weeks 5–8: 5 mg — first maintenance level
- Weeks 9–12: 7.5 mg — escalation if weight loss is progressing
- Weeks 13–16: 10 mg — further escalation
- Weeks 17–20: 12.5 mg — higher therapeutic dose
- Week 21+: 15 mg — maximum dose
Not everyone reaches the maximum dose. Your prescriber may pause escalation or keep you on a lower dose if side effects develop or if weight loss targets are being met. Individual response varies significantly — what works best for you depends on your personal tolerance and health goals.
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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 Gradual Increases Reduce Side Effects
Starting at a low dose and increasing gradually gives your body time to tolerate gastrointestinal side effects like nausea and diarrhoea. These effects often improve as your system adjusts to the medication. Rapid dose increases would likely cause more severe, distressing side effects.
Your prescriber uses dose titration to find your optimal therapeutic dose — the dose that provides the best balance between weight loss benefit and tolerability for your individual circumstances. This is why NHS specialists monitor you closely throughout the titration period and why missing doses or jumping doses is not recommended.
- 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 directly to a higher Mounjaro dose without starting at 2.5 mg?
No. NHS guidance and the product licence require starting at 2.5 mg and escalating gradually at 4-week intervals. Skipping steps would increase side effect risk without clinical benefit. Your prescriber will follow the standard titration schedule.
What happens if I have bad side effects at a particular Mounjaro dose?
Contact your prescriber immediately. You may stay on your current dose longer, reduce back to a lower dose, or stop treatment. Your prescriber will assess your symptoms and decide the best approach based on your individual health and weight loss progress.
Does everyone reach the 15 mg maximum Mounjaro dose?
No. Many people achieve their weight loss goals at lower doses like 5 mg, 7.5 mg, or 10 mg. Your prescriber will not escalate further if you're seeing good results and tolerating the medication well. The maximum dose is available, not mandatory.
How long does Mounjaro dose titration take in the UK?
Standard titration takes approximately 20 weeks (5 months) to reach 15 mg if you escalate at every step. However, your prescriber may pause, repeat, or skip steps based on your response, so your individual timeline may be shorter or longer.
Can I use the GLP-1 weight loss calculator to predict my results during dose titration?
Yes, our free GLP-1 weight loss calculator can help you estimate potential outcomes at different doses based on clinical trial data. Remember that individual results vary — your actual weight loss depends on diet, activity, and personal metabolism alongside your Mounjaro dose.
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.