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 Much Will Mounjaro Increase By?
Mounjaro (tirzepatide) uses a gradual dose escalation schedule called titration. Your starting dose is 2.5 mg per week, and the dose increases every 4 weeks if tolerated well, stepping up through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally to a maximum of 15 mg. Each KwikPen contains 4 weekly doses. Your prescriber will manage the pace of increases based on your individual tolerance and response. This structured approach helps your body adjust to the medication while minimising side effects.
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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.
The Mounjaro Dose Titration Schedule
Mounjaro follows a consistent titration pattern designed to help your body adapt gradually. Starting at 2.5 mg (weeks 1–4), the dose then moves to 5 mg (weeks 5–8), the first full maintenance dose. From there, if your prescriber determines escalation is appropriate, you'll increase by 2.5 mg increments every 4 weeks: 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg, which is the maximum licensed dose.
Each increase represents a step up in the KwikPen device itself—you'll receive a new pen with the new dose marked on it. You never manually adjust doses. Your prescriber controls when (and if) you move to the next step based on how well you're tolerating the medication and your weight loss response. Some people reach an effective dose at 5 mg or 7.5 mg and stay there; others titrate to the full 15 mg. The minimum time between dose increases is always 4 weeks.
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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.
What to Expect During Dose Increases
When you step up to a new Mounjaro dose, it's normal to experience temporary side effects like mild nausea, appetite changes, or digestive symptoms. These often settle within the first week or two as your body adjusts. Staying hydrated, eating small frequent meals, and moving gently can help manage these symptoms.
If you experience severe or persistent side effects at any dose, contact your prescriber immediately—they may delay the next increase or keep you at your current dose longer. Use our free BMI calculator alongside your Mounjaro progress to track how your weight responds at each dose level, and use our GLP-1 weight loss calculator to see projected outcomes at different doses.
- 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 is the first dose of Mounjaro?
The first dose is always 2.5 mg per week for the first 4 weeks. This is the starting/adjustment dose, not a full maintenance dose. It helps your body tolerate the medication before moving to higher doses.
How much does the dose increase each time?
Each increase is 2.5 mg. So 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg. The steps are uniform, making the escalation predictable and manageable.
Can my prescriber skip dose increases or keep me at a lower dose?
Yes. Your prescriber may decide to stop titration at any point if you're getting good results or tolerating the medication well at your current dose. There's no requirement to reach 15 mg.
What if I get side effects when the dose increases?
Contact your prescriber. They may delay your next increase, keep you at your current dose longer, or manage symptoms while you adjust. Side effects often improve within days to weeks.
How is Mounjaro dosed differently from Wegovy?
Mounjaro (tirzepatide) starts at 2.5 mg and increases to 15 mg. Wegovy (semaglutide) starts at 0.25 mg and increases to 2.4 mg. Both are once-weekly injections requiring prescription-only clinical assessment. Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1 only.
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.