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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Dizziness on Mounjaro vs Wegovy — What You Need to Know
Dizziness can occur when taking weight loss injections like Mounjaro or Wegovy, though it is not listed as a very common side effect with either medication. Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are prescription-only GLP-1 receptor agonists used for weight management in the UK, and they work through similar mechanisms but with some key differences. Understanding how dizziness compares between the two can help you and your GP make an informed decision about which medication may be more suitable for your individual health needs.
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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 and Wegovy Differ — Clinical Context
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways rather than one. Wegovy (semaglutide) is a GLP-1 receptor agonist only. This dual mechanism in Mounjaro may contribute to different side effect profiles, though both medications can cause dizziness in some users.
Clinical trial data shows dizziness is listed as a common side effect (affecting up to 1 in 10 people) with both medications. In the SURMOUNT-1 trial for Mounjaro, dizziness was reported by a minority of participants. Similarly, in the STEP trials for Wegovy, dizziness occurred but was not among the most frequently reported side effects. The exact incidence varies between individuals, and factors like dose escalation, hydration status, and blood pressure changes may influence whether dizziness develops.
- Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg weekly
- Wegovy starts at 0.25 mg and escalates to a maximum of 2.4 mg weekly
- Both require minimum 4 weeks at each dose before increasing
- Slower dose escalation may reduce dizziness risk
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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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Which Medication Is Right for You — Individual Suitability
Neither Mounjaro nor Wegovy is "better" for dizziness—the best choice depends on your individual health profile, medical history, and how your body responds to GLP-1 therapy. Some people experience dizziness with one medication and not the other; others experience neither. A UK-licensed prescriber will assess factors including your current blood pressure, blood sugar control, other medications, and any history of dizziness or balance problems.
If you experience dizziness while taking either medication, report it to your prescriber immediately. This may warrant dose adjustment, slower escalation, or a switch to the alternative medication. Never stop taking a weight loss injection without medical guidance. Both Mounjaro and Wegovy require ongoing clinical assessment, and your prescriber can adjust your treatment plan based on your individual response and side effects.
- 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 dizziness more common on Mounjaro or Wegovy?
Dizziness is listed as a common side effect for both medications (affecting up to 1 in 10 people in clinical trials). There is no clear evidence that one causes dizziness more frequently than the other. Individual response varies significantly, and factors like dose, hydration, and blood pressure changes influence likelihood.
What causes dizziness on GLP-1 weight loss injections?
Dizziness with GLP-1 medications like Mounjaro and Wegovy may result from several factors: reduced food intake leading to lower blood sugar, changes in blood pressure, dehydration, or the medication's effect on gastric emptying. Dizziness is often temporary and may resolve as your body adjusts.
Can I switch from Mounjaro to Wegovy if I experience dizziness?
Potentially, yes—but only under prescriber guidance. Your GP or weight management specialist can assess whether switching is appropriate and manage any transition carefully. They may alternatively adjust your dose or escalation schedule rather than switching medications.
What should I do if I feel dizzy on Mounjaro or Wegovy?
If dizziness occurs, stay hydrated, sit or lie down immediately, and avoid driving or operating machinery. Inform your prescriber as soon as possible. Do not stop taking your injection without medical advice. Your prescriber may adjust your dose, slow your escalation, or explore other causes.
Are there other common side effects I should expect besides dizziness?
Yes. Very common side effects with both medications include nausea, diarrhoea, vomiting, and constipation. Common side effects include indigestion, headache, fatigue, and injection site reactions. Most side effects improve as your body adjusts, but always report persistent or severe symptoms to your GP.
Ready to take control of your weight loss journey?
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