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
Free tracker included with every download this week
Why Am I Dizzy on Mounjaro?
Dizziness is a reported side effect of Mounjaro (tirzepatide), the prescription-only weight management injection available in the UK. While not everyone experiences it, dizziness can occur as your body adjusts to the medication, particularly in the first few weeks or when your dose increases. Understanding why this happens and when to seek help is important for your safety and ongoing treatment.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
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.
Common Causes of Dizziness on Mounjaro
Dizziness while taking Mounjaro can happen for several reasons related to how the medication works:
- Blood sugar changes: If you're also managing type 2 diabetes, Mounjaro may lower your blood sugar levels, which can cause lightheadedness or dizziness
- Dehydration: Mounjaro commonly causes nausea, vomiting, and diarrhoea — all of which increase fluid loss and can lead to dizziness
- Rapid stomach emptying: In the first weeks, Mounjaro slows how quickly food leaves your stomach, which can affect blood pressure regulation and cause dizziness
- Low blood pressure: Some people experience a temporary drop in blood pressure when starting tirzepatide
- Dose adjustment: Dizziness is more common when increasing from one dose to the next (every 4 weeks in the dose titration schedule)
These effects typically improve as your body adjusts, usually within 1–2 weeks of starting or increasing your dose.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
When to Contact Your GP — Serious Warning Signs
While mild dizziness often resolves on its own, certain symptoms warrant urgent medical attention. Contact your GP immediately if you experience: severe dizziness preventing you from standing or moving safely, dizziness combined with chest pain or shortness of breath, fainting or loss of consciousness, persistent dizziness lasting more than a few days, or dizziness alongside severe stomach pain (which may indicate pancreatitis). Your GP can assess whether the dizziness is related to Mounjaro or another health condition. Never stop taking Mounjaro without medical guidance — your prescriber can adjust your dose or suggest alternative treatments if dizziness is significantly affecting your quality of life.
- 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 not listed as a very common side effect but is reported by some people taking tirzepatide. It tends to occur more frequently when starting treatment or increasing doses. Most cases improve within 1–2 weeks as your body adjusts. If dizziness persists or worsens, contact your prescriber for guidance.
How can I reduce dizziness while taking Mounjaro?
Stay well hydrated by drinking plenty of water throughout the day. Eat small, frequent meals to maintain stable blood sugar. Rise slowly from sitting or lying down to avoid sudden dizziness. Avoid hot environments where dehydration worsens. If nausea or vomiting is causing fluid loss, inform your GP. Our GLP-1 weight loss calculator can help you understand how your dose affects your body.
Is dizziness more likely at higher Mounjaro doses?
Yes, dizziness is more commonly reported when starting Mounjaro (at 2.5 mg) or when increasing to higher doses (5 mg, 10 mg, 15 mg). The dose titration schedule spaces increases 4 weeks apart to allow your body to adjust. If dizziness occurs during escalation, your prescriber may delay the next increase or adjust your treatment plan.
Can dizziness mean Mounjaro isn't working for weight loss?
No — dizziness is a side effect unrelated to whether Mounjaro is helping you lose weight. Many people experience dizziness early on but still achieve good weight loss results as side effects settle. Results vary between individuals, and our BMI calculator can help you track your progress alongside your weight loss journey.
Should I stop taking Mounjaro if I feel dizzy?
Do not stop Mounjaro without speaking to your prescriber first. Stopping suddenly may not be appropriate. Instead, contact your GP or the clinician who prescribed Mounjaro and describe your symptoms. They can assess whether the dizziness is expected, recommend management strategies, or adjust your dose if necessary.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.