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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Mounjaro Dose Increase vs Wegovy: What's the Difference?
If you're considering prescription weight loss treatment in the UK, you may wonder how Mounjaro's dose escalation compares to Wegovy. Both are once-weekly injections approved for weight management, but they work differently and follow distinct dosing schedules. Understanding the key differences—including how their doses increase over time, their underlying mechanisms, and clinical trial results—helps you and your prescriber make an informed choice. Both medications require a prescription and clinical assessment to determine which is right for your individual circumstances.
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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.
Dose Escalation Schedules: Mounjaro vs Wegovy
Mounjaro (tirzepatide) uses a 4-week dose escalation schedule, starting at 2.5 mg and increasing to a maximum of 15 mg once weekly. You remain on each dose for a minimum of 4 weeks before your prescriber may increase it, giving your body time to adjust. The progression is: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg.
Wegovy (semaglutide) follows a 4-week escalation pattern as well, but with lower maximum doses. It starts at 0.25 mg and reaches a maximum of 2.4 mg once weekly. The progression is: 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg.
Both medications allow your body to gradually adapt to the medication, which may help reduce side effects like nausea. Clinical trials showed that many people tolerate the dose increases well when they follow the prescribed timeline. Your prescriber will assess your individual tolerance and may adjust the schedule if needed.
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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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Clinical Trial Data and Individual Suitability
In the SURMOUNT-1 trial, Mounjaro showed average weight loss of approximately 15% of body weight at 5 mg, rising to 20.9% at the maximum 15 mg dose over 72 weeks. In the STEP-1 trial, Wegovy showed average weight loss of approximately 14.9% at its maximum 2.4 mg dose over 68 weeks. Both results were achieved alongside a reduced-calorie diet and increased physical activity, and individual results varied considerably.
Neither medication is "better"—the choice depends on your individual health profile, any existing conditions, and how your body responds. Your GP or prescriber will assess whether Mounjaro's dual GIP and GLP-1 mechanism or Wegovy's single GLP-1 mechanism suits you better. Use our free GLP-1 weight loss calculator to explore potential outcomes, and your prescriber will guide the final decision.
- 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.
How much higher does Mounjaro dose go compared to Wegovy?
Mounjaro's maximum dose is 15 mg once weekly, whilst Wegovy's maximum is 2.4 mg once weekly. This reflects their different mechanisms—Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is a single GLP-1 agonist. The higher absolute dose in Mounjaro does not necessarily mean greater weight loss; both work differently in the body.
Do both medications increase at the same speed?
Yes, both follow a 4-week escalation schedule, meaning you stay on each dose for at least 4 weeks before increasing. This allows your body time to adjust and may help manage side effects like nausea and stomach discomfort.
Which medication causes more side effects during dose increase?
Both can cause nausea, stomach upset, and constipation, particularly during the first few weeks and when doses increase. Side effects often improve as your body adjusts. Your prescriber will monitor your tolerance and may adjust the schedule if needed. Keep a record of how you feel using our free progress tracker.
Can my prescriber switch me from Mounjaro to Wegovy mid-treatment?
Yes, switches between medications are possible, though not routine. There is no official conversion chart—any switch must be managed by your prescriber, typically involving a dose adjustment period. Your prescriber will make this decision based on your individual response and tolerance.
Why do some people stay on lower doses instead of reaching the maximum?
Not everyone needs or tolerates the maximum dose. Some people achieve their weight loss goals at lower doses. Your prescriber will increase your dose only if you tolerate it well and further increases are clinically appropriate. Individual responses vary significantly.
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.