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 (tirzepatide) is prescribed in gradually increasing doses rather than starting at the maximum strength. This process, called dose titration, helps your body adjust to the medication while monitoring how well it's working and managing side effects. Your prescriber will increase your dose every 4 weeks based on your tolerance and response. Understanding why this approach is used helps you get the most from your prescription-only treatment.
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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
Dose titration is the controlled, stepwise increase in Mounjaro strength over weeks. You start at 2.5 mg once weekly for 4 weeks, then progress through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to the maximum 15 mg — spending at least 4 weeks on each dose before escalation. This gradual approach serves three key purposes: it allows your digestive system time to adapt to the medication (reducing nausea and stomach discomfort), it helps your prescriber identify the lowest effective dose for you, and it ensures any side effects remain manageable. Each dose is delivered via a pre-filled KwikPen as a once-weekly injection. Your GP or specialist will assess your progress at each step and may pause escalation if side effects are significant, or continue if you're tolerating the medication well. Clinical trials showed that dose escalation leads to greater average weight loss — those reaching 15 mg in studies achieved approximately 21% body weight reduction compared to lower doses — but individual results vary considerably.
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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 Your Prescriber Won't Start You at Maximum Dose
Starting Mounjaro at 2.5 mg instead of 15 mg protects your health in several ways. Your gut contains GLP-1 receptors that trigger feelings of fullness and slow gastric emptying. A high initial dose would activate these intensely, causing severe nausea, vomiting, and diarrhoea in most patients — side effects that often lead to stopping the medication entirely. Gradual escalation allows your body to build tolerance, so by the time you reach higher doses, these side effects typically reduce. Additionally, your prescriber learns how your individual body responds. Some people achieve their weight loss goals at 5 mg or 7.5 mg, so pushing to 15 mg unnecessarily exposes them to more side effects and cost without added benefit. Use our free GLP-1 weight loss calculator to explore how different doses might support your goals, and discuss your personal dose plan with your prescriber.
- 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 can't tolerate a dose increase?
Your prescriber can keep you on your current dose longer or pause escalation entirely. If you achieve your weight loss goals at 10 mg, there's no medical reason to increase further. Some patients stay on a lower dose indefinitely. Always tell your prescriber about side effects — they can adjust your plan.
Can I increase Mounjaro faster than the 4-week schedule?
No — the prescribing guidance recommends at least 4 weeks between dose increases. This gives your body adequate time to adapt. Increasing faster significantly increases the risk of severe nausea and vomiting without providing additional benefit.
Is there a dose where most people see weight loss results?
Clinical trials showed meaningful weight loss starting at 5 mg, with greater average loss at 10 mg and 15 mg. However, individual results vary widely. Some people see significant results at 5 mg; others need 15 mg. Your prescriber will find your effective dose.
Why does Mounjaro cost more at higher doses?
Higher doses contain more active ingredient (tirzepatide). A 15 mg dose costs more than a 5 mg dose. If you achieve your goals at a lower dose, you can stay there and pay less — discuss cost considerations with your prescriber.
How do I know if I should stay on my current dose or increase?
Your prescriber reviews your weight loss progress, side effects, and health goals at each 4-week mark. If you're losing weight steadily and side effects are manageable, escalation typically continues. If you're meeting your goals or side effects are problematic, staying on your current dose is a valid option.
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.