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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7.5 Mg Mounjaro Side Effects vs Wegovy
At the 7.5 mg dose, Mounjaro (tirzepatide) and Wegovy (semaglutide) both carry similar but distinct side effect profiles. The key difference lies in their mechanisms: Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy activates GLP-1 only. This means the two medications work in slightly different ways in your body, which can influence how side effects present. Both are prescription-only weight management injections licensed in the UK. Understanding the differences can help your prescriber choose the right option for you following a clinical assessment. Our GLP-1 weight loss calculator can also help you explore potential outcomes with either medication.
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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.
Clinical Trial Data and Mechanism Differences
Mounjaro mechanism: Activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors, producing a dual hormonal effect. At 7.5 mg during SURMOUNT trials, participants experienced robust appetite regulation and increased feelings of fullness.
Wegovy mechanism: Activates GLP-1 only, a single-pathway approach proven effective across STEP trials. Wegovy reaches equivalent clinical effects at higher cumulative doses due to its single-agonist design.
Side effect profile similarities: Both medications commonly cause nausea, diarrhoea, constipation, vomiting, and abdominal discomfort—particularly during dose titration. These typically improve as your body adjusts.
- Nausea: very common with both, usually mild to moderate
- Gastrointestinal symptoms: diarrhoea or constipation depending on individual response
- Injection site reactions: bruising or redness, generally mild
- Fatigue: reported by some users during first weeks
The dual mechanism of Mounjaro may theoretically produce slightly different gastrointestinal tolerability, though individual variation is significant. Your prescriber's experience with each medication and your personal health history will guide the choice.
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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.
Choosing Between 7.5 Mg Mounjaro and Wegovy: Prescriber Assessment
Neither medication is inherently superior—suitability depends on your individual health profile, previous medication responses, and clinical goals. Your GP or licensed prescriber will assess which is appropriate during your consultation.
Factors that influence choice: Type 2 diabetes history (Mounjaro has additional blood sugar benefits from its GIP action), previous side effect tolerance, kidney function, and personal preference regarding injection frequency. Both require a UK prescription and clinical assessment before supply.
If you're eligible for NHS specialist weight management services, your tier 3 team will recommend based on current guidance. If accessing privately, your online prescriber will discuss which medication aligns with your health profile. Using our BMI calculator alongside your assessment can help illustrate your current health classification and provide context for discussion 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.
Is Mounjaro 7.5 mg stronger than Wegovy for weight loss?
Not necessarily. Mounjaro's dual mechanism (GIP + GLP-1) and Wegovy's single mechanism (GLP-1) produce different pathways to similar weight loss outcomes. SURMOUNT trials showed Mounjaro averaging 15–clinically studied weight loss; STEP trials showed Wegovy averaging ~15%. Results vary individually. Prescriber assessment determines suitability.
Do Mounjaro and Wegovy cause the same side effects at similar doses?
Both cause nausea, diarrhoea, constipation, and abdominal discomfort as very common side effects. The frequency and severity can differ between individuals and between medications due to their different mechanisms. Most side effects improve within weeks as your body adjusts to the medication.
Which medication has fewer gastrointestinal side effects?
Neither has significantly fewer GI side effects overall—both slow gastric emptying and commonly cause nausea and bowel changes. Individual tolerance varies greatly. Your prescriber may recommend one over the other based on your previous medication responses and digestive health history.
Can I switch from Mounjaro to Wegovy if I experience side effects?
Switching between medications should only be done under prescriber guidance. It's not a simple swap—doses are not directly equivalent. If you experience troublesome side effects, your prescriber may adjust your current medication's dose, timing, or dietary approach before considering a switch to the alternative.
How do I know which medication my GP or prescriber will recommend?
Your prescriber will consider your BMI, weight-related health conditions, previous medication responses, kidney function, and personal preference. Both are UK prescription-only, requiring clinical assessment. NICE and NHS guidance support both; regional availability varies. Your individual health profile drives the choice, not superiority of one over the other.
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.