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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Mounjaro Dizziness vs Wegovy — What's the Difference?
Dizziness can occur with both Mounjaro (tirzepatide) and Wegovy (semaglutide) weight loss injections, though it's not listed as a very common side effect with either medication. The two injections work differently — Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. This difference in mechanism may influence how your body responds, including whether you experience dizziness during treatment. Both are prescription-only medicines in the UK, and side effects vary significantly between individuals. Your prescriber can help assess which medication may be more suitable based on your personal health profile and medical history.
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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 Compare for Dizziness
Clinical trial data shows both medications list dizziness as a potential but uncommon side effect. In SURMOUNT-1 trials (Mounjaro), dizziness was reported in a small percentage of participants across all dose groups. Similarly, in STEP-1 trials (Wegovy), dizziness occurred in a minority of users. The difference lies in their mechanisms: Mounjaro activates both GIP and GLP-1 pathways, whilst Wegovy targets GLP-1 alone. This dual action in Mounjaro may theoretically influence side effect profiles, though individual responses vary considerably.
Common side effects with both injections include nausea, diarrhoea, vomiting, and constipation — gastrointestinal symptoms that can sometimes lead to dehydration, which itself may cause dizziness. Dizziness may also be related to rapid blood sugar changes or dose escalation.
- Mounjaro: doses escalate from 2.5 mg to 15 mg weekly over 20 weeks
- Wegovy: doses escalate from 0.25 mg to 2.4 mg over 16 weeks
Both require clinical assessment before prescription. Use our free GLP-1 weight loss calculator to explore projected outcomes with either medication, and always inform your prescriber of any dizziness during treatment.
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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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Individual Suitability and Clinical Assessment
Whether you experience dizziness with Mounjaro, Wegovy, or neither depends on your individual physiology, other medications you take, underlying health conditions, and dose escalation speed. Some people tolerate one injection far better than the other, whilst others experience minimal side effects on either.
Your prescriber will assess which medication is most suitable for you based on your BMI, weight-related health conditions (such as type 2 diabetes or high blood pressure), current medications, and medical history. If you develop dizziness on one medication, this does not necessarily mean you'll experience it on the other — your prescriber may adjust your dose, alter escalation timing, or discuss switching options if appropriate.
Always report any dizziness, lightheadedness, or concerning symptoms to your GP or prescriber immediately. Keep a symptom diary during the first few weeks of treatment to help your healthcare team identify patterns.
- 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 listed as a potential side effect of Mounjaro but is not classified as "very common" or "common" in clinical trial data. It occurs in a small percentage of users. Most common side effects are gastrointestinal — nausea, diarrhoea, vomiting, and constipation. If you develop persistent dizziness, contact your GP or prescriber.
Does Wegovy cause dizziness more or less than Mounjaro?
Both medications report dizziness in a similar low percentage of users. Wegovy is a GLP-1 agonist only, whilst Mounjaro is a dual GIP and GLP-1 agonist, so their mechanisms differ. However, clinical trial data doesn't show Wegovy as significantly more or less likely to cause dizziness than Mounjaro. Individual responses vary greatly.
What should I do if I feel dizzy whilst taking Mounjaro or Wegovy?
If you experience dizziness, ensure you stay hydrated, as gastrointestinal side effects can lead to dehydration. Sit or lie down until the dizziness passes. If dizziness is severe, persistent, or worsens, contact your GP or prescriber immediately. Do not drive or operate machinery whilst dizzy.
Can I switch from Mounjaro to Wegovy if I get dizziness?
Possible dose-related changes or medication switches require prescriber guidance. Your GP or weight management specialist can assess whether adjusting your current dose, changing your escalation schedule, or switching medications is appropriate. Never stop or switch medications without medical advice.
Is dizziness a sign I should stop taking the injection?
Not necessarily. Dizziness may be temporary, dose-related, or caused by dehydration rather than the medication itself. However, always report new or worsening dizziness to your prescriber. They can determine whether it's a side effect requiring monitoring, dose adjustment, or if switching medications is more appropriate. Never stop without discussing it with your healthcare team.
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