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: NHS Guide to This Common Side Effect
Dizziness is a common side effect reported by some people taking Mounjaro (tirzepatide) in the UK. It typically occurs in the first few weeks after starting the injection or during dose increases, and often improves as your body adjusts. This NHS-aligned guide explains why dizziness happens, when to seek help, and what you can do to manage it safely.
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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.
Why Does Mounjaro Cause Dizziness?
Dizziness with Mounjaro typically happens for two main reasons. First, rapid blood sugar changes can occur, especially if you're also taking diabetes medications like insulin or sulphonylureas — when blood sugar drops too quickly, dizziness is a natural response. Second, Mounjaro slows how quickly food leaves your stomach, which can temporarily affect blood pressure and fluid balance, leading to lightheadedness.
Dehydration is another common trigger — many people report nausea and reduced appetite when taking Mounjaro, which may lead to drinking less water. Low fluid intake combined with the medication's effects can cause dizziness, particularly when standing up quickly (orthostatic hypotension). Dizziness is listed as a common side effect in UK prescribing information, affecting up to 1 in 10 people, and usually resolves within the first 4 weeks as your body adjusts to the tirzepatide dose.
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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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Managing Dizziness and When to See Your GP
If you experience dizziness while taking Mounjaro, start by staying well hydrated — aim for at least 6–8 glasses of water daily, even if you don't feel thirsty. Rise slowly from sitting or lying down, and avoid sudden position changes. Eat small, regular meals to help stabilise blood sugar levels. If you're taking other diabetes medications, your GP may recommend adjusting these doses once you start Mounjaro.
Contact your GP if: dizziness is severe or persistent beyond 4 weeks, you have fainting episodes, dizziness occurs with chest pain or shortness of breath, or you're unsure whether your other medications need adjustment. Your prescriber can review whether your current Mounjaro dose is right for you and whether any other medications require modification.
- 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 normal side effect of Mounjaro?
Yes — dizziness is a common side effect affecting up to 1 in 10 people taking Mounjaro. It typically occurs during the first few weeks and often improves as your body adjusts. However, if dizziness persists beyond 4 weeks or is severe, contact your GP to rule out other causes or medication interactions.
Can dizziness with Mounjaro be dangerous?
Mild dizziness is usually not dangerous, but it can increase fall risk, especially in older adults. Severe dizziness or fainting is less common and should be reported to your GP immediately. Dizziness combined with chest pain, shortness of breath, or vision changes requires urgent medical attention.
How long does dizziness last when taking Mounjaro?
Most people experience dizziness only in the first 2–4 weeks after starting Mounjaro or increasing the dose. It typically resolves as your body adapts to the medication. If dizziness continues beyond this period, inform your prescriber — it may indicate a need to adjust your Mounjaro dose or review other medications.
Does dizziness happen at every Mounjaro dose increase?
Not necessarily. Some people experience dizziness only at the starting dose (2.5 mg), while others may feel dizzy again during dose escalation. Your GP or prescriber can help manage this by adjusting how quickly you increase doses or reviewing other medications that might contribute to dizziness.
What's the difference between dizziness and vertigo with Mounjaro?
Dizziness is lightheadedness or feeling faint, while vertigo is a spinning sensation. Both can occur with Mounjaro, but vertigo is less common. If you experience true vertigo (the room spinning), contact your GP — it may indicate a separate condition unrelated to the medication.
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