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
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Why Is Mounjaro Going Up — Mounjaro vs Wegovy
Mounjaro doses increase gradually over time as part of a structured titration schedule — this is intentional and designed to help your body adjust. If you're considering weight loss medication in the UK, understanding how Mounjaro's dose progression works and how it differs from alternatives like Wegovy can help you make an informed decision. Both are prescription-only GLP-1 based medications, but they work in different ways and have different dose patterns. This guide explains why doses go up, how the two medications compare, and what to expect from each option.
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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 vs Wegovy
Mounjaro (tirzepatide) follows a structured 4-week dose escalation schedule designed to minimise side effects and allow your body to adapt. You start at 2.5 mg weekly, increasing every 4 weeks through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally to 15 mg (the maximum dose). In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight across these doses.
Wegovy (semaglutide) uses a similar but different escalation, starting at 0.25 mg and increasing through 0.5 mg, 1 mg, 1.7 mg, and reaching 2.4 mg at week 17. The STEP-1 clinical trial showed average weight loss of approximately 14.9% at the maximum dose.
- Mounjaro is a dual GIP and GLP-1 agonist (two hormone pathways activated)
- Wegovy is a GLP-1 agonist only (single hormone pathway)
- Both are prescription-only and require clinical assessment
- Individual results vary significantly regardless of medication
Your GP or prescriber will assess which is more suitable for you based on your health profile, BMI, and any weight-related conditions. Use our free BMI calculator to check your current status and understand your starting point.
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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.
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Side Effects, Suitability, and Making Your Choice
Dose increases are gradual because nausea and stomach upset are common early side effects for both medications. Spreading doses over weeks allows these to settle before escalating. Most people experience the worst effects in weeks 1–2 of each new dose, then adapt over the following weeks.
Both Mounjaro and Wegovy require a prescription following clinical assessment — your prescriber will consider your BMI, weight-related health conditions (like type 2 diabetes or high blood pressure), medical history, and other medications. Neither is suitable for pregnant individuals, those under 18, or people with a history of certain thyroid or pancreatic conditions.
Access in the UK is through either NHS specialist tier 3 weight management services (with potential waiting lists) or private online prescribing services. Try our free GLP-1 weight loss calculator to project potential outcomes at different doses, and track your progress with our free progress tracker if you begin treatment.
- 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.
Why does Mounjaro dose go up every 4 weeks?
The 4-week cycle allows your body to adjust to each dose and for nausea and other side effects to settle before increasing. This gradual escalation helps you tolerate the medication better and reduces the risk of severe side effects. Your prescriber will only increase your dose if you're managing well on your current level.
Is Mounjaro better than Wegovy for weight loss?
Clinical trials show Mounjaro may produce slightly higher average weight loss (15–21% vs 14.9%), but individual results vary significantly. The "better" medication depends on your personal health profile, how you tolerate each medication, and your prescriber's assessment. Neither is assured to work the same way for everyone.
Can I skip a Mounjaro dose increase if I'm struggling with side effects?
Yes — speak to your prescriber if you're experiencing difficult side effects. They may delay your dose increase, keep you on your current dose longer, or in some cases switch you to a different medication. Never increase doses on your own or skip doses without guidance.
How do I access Mounjaro or Wegovy on the NHS in the UK?
Ask your GP for a referral to your local tier 3 specialist weight management service. NHS access is available but varies by region and can involve waiting lists. Private online prescribing services are also available in the UK if NHS access isn't immediate for you.
What's the difference between Mounjaro and Ozempic?
Mounjaro (tirzepatide) is licensed for weight management at doses up to 15 mg. Ozempic (semaglutide) is licensed for type 2 diabetes only, at doses up to 2 mg, and is not approved for weight loss in the UK. Wegovy is the licensed weight management version of semaglutide at higher doses.
Ready to take control of your weight loss journey?
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