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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Dizzy Mounjaro vs Wegovy — Which Is Better for You?
Dizziness is a side effect that some people experience when taking Mounjaro (tirzepatide), though it's not among the most common ones reported in clinical trials. If you're experiencing dizziness on Mounjaro and wondering whether Wegovy might be a better option, it's important to understand how these two medications differ and what the evidence actually shows. Both are prescription-only weight management injections licensed in the UK, but they work through different mechanisms. This guide explains the key differences, what causes dizziness on these medications, and how to discuss your symptoms with your prescriber.
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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.
Mounjaro vs Wegovy — Mechanism, Trials, and Dizziness Context
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways in the body. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single pathway. This difference in mechanism may influence how people respond to each medication, including side effects like dizziness.
The clinical trials supporting each medication showed different side effect profiles. The SURMOUNT-1 trial for Mounjaro (at 15 mg maximum dose) reported dizziness as an uncommon side effect. The STEP-1 trial for Wegovy (at 2.4 mg maximum dose) similarly reported dizziness as uncommon. Average weight loss was approximately 20.9% with Mounjaro 15 mg and 14.9% with Wegovy 2.4 mg at 68–72 weeks, though individual results vary significantly.
Dizziness on either medication can result from several factors: rapid blood sugar changes, dehydration, dose escalation speed, or interactions with other medications. It's not necessarily a reason to switch medications — many people experience temporary dizziness during dose titration that resolves as their body adjusts.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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When to Discuss Symptoms With Your Prescriber
If you're experiencing dizziness on Mounjaro, the first step is to contact your prescriber rather than stopping the medication or self-switching to another injection. Dizziness can often be managed by slowing your dose titration, ensuring adequate hydration, checking blood sugar levels (if diabetic), or reviewing other medications that might interact.
Your prescriber may suggest staying on your current Mounjaro dose longer before escalating, reducing your dose temporarily, or investigating other causes of dizziness. Switching to Wegovy is an option some people explore, but it requires a new prescription and clinical assessment. Neither medication is universally "better" — suitability depends on your individual health, other medications, and how your body responds. Only your GP or weight management prescriber can advise which medication is right for you.
- 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 a common side effect of Mounjaro?
Dizziness is uncommon with Mounjaro based on clinical trial data, though some people do experience it. It's more likely during dose escalation and often resolves as the body adjusts. Always report dizziness to your prescriber rather than stopping the medication.
Does Wegovy cause less dizziness than Mounjaro?
Clinical trial data shows dizziness is uncommon with both medications. Individual experiences vary considerably. The difference in mechanisms (dual vs single pathway) doesn't assures different dizziness rates — it depends on your personal response. Your prescriber can advise based on your health history.
What causes dizziness on weight loss injections?
Dizziness on Mounjaro or Wegovy can result from blood sugar fluctuations, dehydration, rapid dose increases, or medication interactions. Slowed gastric emptying may also affect how quickly medications are absorbed. Staying hydrated and eating regular meals often helps.
Can I switch from Mounjaro to Wegovy if I'm dizzy?
Switching is possible but requires a new prescription and clinical assessment from your GP or prescriber. Before switching, discuss whether your dizziness might resolve with adjustments to your current Mounjaro dose, timing, or hydration. Switching isn't always necessary.
What should I do if I feel dizzy on Mounjaro?
Contact your prescriber immediately — don't stop taking it without guidance. Ensure you're drinking enough water, eating regular meals, and not taking the injection too quickly after eating. Your prescriber may adjust your dose schedule or investigate other causes before considering a medication change.
Ready to take control of your weight loss journey?
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