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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Is Dizziness A Side Effect Of Mounjaro?
Dizziness is reported as a side effect in some people taking Mounjaro (tirzepatide), though it is not one of the most common reactions. Both Mounjaro and Wegovy can cause dizziness during the adjustment period, typically when starting or increasing doses. Individual responses vary significantly between users. This guide compares dizziness risk between these two prescription weight management injections, drawing on UK clinical trial data and prescriber experience. Understanding potential side effects helps you make an informed decision with your GP or licensed prescriber about which medication might suit you.
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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.
Dizziness In Mounjaro vs Wegovy Clinical Trials
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 receptor agonist only. This mechanism difference may influence side effect profiles. In the SURMOUNT-1 clinical trial, dizziness was reported by a small percentage of participants on tirzepatide, though it was not classified as "very common" or "common". Wegovy, based on the STEP-1 trial, reports dizziness at similar rates — affecting a minority of users but not listed as a frequent adverse event. Both medications can cause dizziness through several mechanisms: rapid blood sugar changes, dehydration from gastrointestinal side effects (nausea, diarrhoea), or blood pressure shifts. The dual mechanism of Mounjaro does not necessarily make dizziness more likely than Wegovy. Instead, individual factors like baseline blood pressure, hydration status, and dose titration speed play larger roles. Most dizziness cases reported in trials were mild to moderate and improved with continued use.
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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.
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When Dizziness Occurs And Individual Suitability
Dizziness is most likely during dose titration — when you first start a medication or increase your dose. Mounjaro uses a 4-week escalation schedule (2.5 mg → 5 mg → 7.5 mg and so on), whilst Wegovy escalates over 16 weeks with smaller incremental steps. A slower titration may reduce dizziness risk, though this varies between individuals. Dehydration significantly increases dizziness — staying well-hydrated and eating small, regular meals helps. If you experience dizziness, inform your prescriber immediately. They may adjust your dose, recommend a slower escalation, or suggest you try the alternative medication. Both Mounjaro and Wegovy require a clinical assessment before prescription — your prescriber will consider your medical history, current medications, and blood pressure to determine which is most suitable for you. Neither medication is universally "safer" regarding dizziness; suitability is individual.
- 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 common with Mounjaro?
Dizziness is not classified as a very common or common side effect of Mounjaro. It affects a small percentage of users, typically during dose adjustments. Most cases are mild and resolve as your body adjusts. If you experience persistent dizziness, contact your prescriber.
Does Wegovy cause dizziness more or less than Mounjaro?
Clinical trial data suggests dizziness occurs at similar rates with both medications. Wegovy uses a slower dose escalation (16 weeks) compared to Mounjaro (4-week steps), which may reduce initial dizziness for some people. Individual responses vary — one medication may suit you better than the other.
What causes dizziness when taking these injections?
Dizziness can result from rapid blood sugar changes, dehydration (especially if experiencing nausea or diarrhoea), or temporary blood pressure shifts. Staying hydrated, eating regularly, and rising slowly from sitting or lying down can help minimise symptoms.
Should I stop taking Mounjaro if I feel dizzy?
Do not stop without consulting your prescriber. Dizziness often improves within days or weeks as your body adjusts. Your GP or licensed prescriber can advise whether to reduce your dose, pause escalation, or try a different approach. Always seek guidance before stopping.
How can I prevent dizziness on Mounjaro or Wegovy?
Drink plenty of water, eat small regular meals, avoid standing too quickly, and get adequate rest. If you have low blood pressure or take blood pressure medication, inform your prescriber — they may adjust your treatment plan. Your prescriber can also slow your dose escalation if needed.
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