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
Dizziness With Mounjaro — What You Need to Know
Dizziness can occur when taking Mounjaro (tirzepatide), though it is not one of the most commonly reported side effects. If you experience dizziness whilst using this prescription weight management injection, it's important to understand whether it's a normal adjustment response or something that needs GP attention. This NHS-aligned guide explains what to expect, when to seek medical advice, and how to manage this symptom safely whilst on Mounjaro treatment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
Why Dizziness Can Occur With Mounjaro
Dizziness with Mounjaro may develop for several reasons related to how the medication works. Rapid blood sugar changes in the early weeks of treatment, particularly if you're also following a reduced-calorie diet, can cause lightheadedness or a spinning sensation. Dehydration is another common trigger—Mounjaro often causes nausea, vomiting, or diarrhoea, which can lead to fluid loss if you're not drinking enough water.
Low blood pressure (hypotension) can also contribute to dizziness, especially when standing up quickly. If you're taking diabetes medications like insulin or sulphonylureas alongside Mounjaro, your blood sugar may drop more than expected, triggering dizziness. Additionally, dose titration (increasing your dose gradually from 2.5 mg through 5 mg, 7.5 mg, 10 mg, 12.5 mg, up to 15 mg) means dizziness may appear or worsen when you move to a higher strength. Most dizziness settles within the first few weeks as your body adjusts, but persistent symptoms always warrant GP review.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 About Dizziness
Contact your GP or NHS 111 if dizziness is severe, persistent beyond the first month, or accompanied by chest pain, shortness of breath, fainting, or vision changes. If you're diabetic and suspect low blood sugar is causing the dizziness, test your blood glucose and seek advice if readings are consistently low. Your GP can review your Mounjaro dosing schedule, check your blood pressure, and assess whether any other medications need adjusting.
If you're accessing Mounjaro privately through online prescribing, contact your prescriber immediately with these symptoms rather than waiting. Do not stop taking Mounjaro without medical guidance. Keep a symptom diary noting when dizziness occurs, how long it lasts, and what you were doing—this information helps your healthcare team make safe decisions about continuing treatment or adjusting your dose.
- 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 in the UK?
Dizziness is listed as a common side effect (affecting up to 1 in 10 people) but is less frequently reported than nausea or stomach pain. Most cases occur during the first few weeks of treatment or after a dose increase. If it persists beyond four weeks or worsens, inform your GP.
Can dehydration from Mounjaro cause dizziness?
Yes. Nausea, vomiting, and diarrhoea caused by Mounjaro can lead to dehydration, which triggers dizziness and lightheadedness. Drink plenty of water throughout the day. If you're experiencing severe vomiting or diarrhoea lasting more than a few hours, contact NHS 111 for advice.
What should I do if I feel dizzy whilst on Mounjaro?
Sit or lie down immediately. Drink water slowly. Avoid sudden position changes. If dizziness occurs with chest pain, fainting, or severe symptoms, call 999. For mild dizziness that's improving, monitor it and report to your GP at your next appointment.
Does dizziness mean Mounjaro isn't working or is unsafe?
Not necessarily. Dizziness is a known adjustment side effect, especially during dose titration. However, it must be assessed by your prescriber or GP to rule out blood pressure drops, blood sugar issues, or other causes. Your healthcare team will decide if your dose should continue, pause, or change.
How long does dizziness last when starting Mounjaro?
Most adjustment-related dizziness settles within 2–4 weeks as your body adapts. If it persists beyond one month, worsens over time, or appears after months of stable treatment, contact your GP. Persistent dizziness may indicate a need to adjust your dose or review other medications.
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.