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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Switching From 7.5mg Mounjaro To Wegovy
If you're currently taking 7.5mg Mounjaro and considering switching to Wegovy, you'll need to understand how the two medications compare in terms of dosing and effectiveness. Although both are prescription-only weight loss injections available in the UK, they work differently — Mounjaro uses a dual GIP and GLP-1 mechanism, whilst Wegovy (semaglutide) is a GLP-1 agonist only. This guide explains the approximate dose equivalence, what switching involves, and how to discuss this with your prescriber. Always consult your GP or the healthcare professional managing your prescription before making any changes.
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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 7.5mg Mounjaro Compares To Wegovy Doses
There is no officially established conversion between Mounjaro and Wegovy — they are different medications with different mechanisms of action. However, based on clinical practice guidance, 7.5mg Mounjaro is approximately equivalent to 1.7mg Wegovy in terms of weight loss effect, though individual responses vary significantly.
- 7.5mg Mounjaro: Dual GIP + GLP-1 agonist (tirzepatide). Clinical trials showed average weight loss of approximately 19.5% body weight at this dose.
- 1.7mg Wegovy: GLP-1 agonist only (semaglutide). Escalation dose in the STEP trial, leading to approximately 14.9% average weight loss at the maximum 2.4mg dose.
The dual action of Mounjaro may produce different results than Wegovy even at approximate equivalence doses. Any switch between these medications must be managed by your prescriber — do not attempt to switch independently. Your GP or weight management specialist will assess whether a change is appropriate for your individual health profile and may recommend a gradual dose adjustment rather than a direct switch.
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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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What To Expect If You Switch To Wegovy
If your prescriber approves switching from Mounjaro to Wegovy, the process typically involves starting Wegovy at a lower dose (usually 0.25mg or 0.5mg) rather than jumping to the approximate equivalent dose. This allows your body to adjust to the single GLP-1 mechanism.
You may experience different side effects on Wegovy compared to Mounjaro — some patients tolerate one better than the other. Nausea, diarrhoea, and appetite changes are common with both, but their timing and intensity may differ. Weight loss progression may also be different because semaglutide works via a single pathway rather than the dual GIP + GLP-1 action of tirzepatide. Keep a record using our free progress tracker to monitor how the new medication affects you, and report any concerns to your prescriber promptly.
- 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 7.5mg Mounjaro the same strength as 1.7mg Wegovy?
No, they are not directly equivalent — Mounjaro and Wegovy are different medications. However, 7.5mg Mounjaro is approximately equivalent to 1.7mg Wegovy in clinical effect. These are approximate comparisons based on clinical practice guidance, not official conversions. Individual results vary significantly, and your prescriber will determine the best approach if switching.
Why would someone switch from Mounjaro to Wegovy?
Reasons for switching may include: intolerance to side effects, lack of desired weight loss effect, personal preference, cost considerations, or prescriber recommendation. Some patients tolerate one medication better than the other. Always discuss with your GP or weight management specialist before switching — never stop or change medications independently.
Is Ozempic the same as Wegovy?
Both Ozempic and Wegovy contain semaglutide, but they are different products. Ozempic is approved for type 2 diabetes (doses up to 2mg). Wegovy is the licensed weight management version (up to 2.4mg). Wegovy is the correct prescription for weight loss in the UK — Ozempic is not licensed for weight loss.
Will I lose the same amount of weight on Wegovy as on Mounjaro?
No — Mounjaro and Wegovy work via different mechanisms, so weight loss outcomes may differ. Mounjaro's dual GIP + GLP-1 action often produces greater average weight loss than Wegovy's single GLP-1 action. However, individual responses vary, and some patients achieve excellent results on Wegovy. Your prescriber will monitor your progress and adjust treatment accordingly.
How do I switch from Mounjaro to Wegovy safely?
Do not switch without your prescriber's guidance. Contact your GP or weight management specialist to discuss your reasons for wanting to switch. They will assess whether it's appropriate, arrange a prescription for Wegovy if approved, and advise on dosing and timing. You'll typically start at a lower Wegovy dose and titrate upwards, rather than jumping to an approximate equivalent dose.
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