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
Dizzy Spells On Mounjaro vs Wegovy — What's Different?
Dizziness can occur with both Mounjaro (tirzepatide) and Wegovy (semaglutide), but they work slightly differently and may affect individuals in varying ways. This guide compares how both prescription weight loss medications approach dizziness as a side effect, what clinical evidence shows, and how your GP or prescriber assesses suitability. Both are GLP-1 based weight management injections licensed in the UK, but Mounjaro adds a dual GIP mechanism, which may influence overall tolerability for some users.
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.
How Mounjaro And Wegovy Differ In Mechanism And Side Effects
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whereas Wegovy (semaglutide) is a GLP-1 agonist only. This mechanistic difference may explain why some individuals experience different side effect profiles. In the SURMOUNT-1 clinical trial, dizziness was reported as a common side effect in some participants on Mounjaro, though it was not among the most frequently reported gastrointestinal symptoms. Wegovy's STEP-1 trial similarly documented dizziness, though typically at mild to moderate severity.
- Mounjaro: dual mechanism (GIP + GLP-1) activates two hormone pathways, which may contribute to overall symptom variation
- Wegovy: single mechanism (GLP-1 only) targets one primary pathway
- Both slow gastric emptying, which can influence blood sugar regulation and potentially trigger dizziness in early weeks
- Dose titration differs: Mounjaro starts at 2.5 mg, Wegovy at 0.25 mg — slower escalation may reduce dizziness risk
Individual tolerability depends on dose, injection frequency, lifestyle factors, and how your body adapts to the medication over time. Neither medication is "better" or "worse" for dizziness — suitability is assessed personally by your prescriber following clinical assessment on the UK prescription Mounjaro KwikPen or Wegovy auto-pen.
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.
What Causes Dizziness And When To Seek GP Advice
Dizziness on GLP-1 medications typically stems from several factors: rapid changes in blood sugar as the medication reduces appetite and food intake; dehydration if nausea reduces fluid intake; or postural hypotension (dizziness when standing quickly). Early weeks on either medication carry higher risk as your body adjusts. Most individuals report improvement after 4–8 weeks as tolerance builds.
Contact your GP if dizziness: is severe or persistent beyond 8 weeks, worsens over time, is accompanied by chest pain or shortness of breath, or interferes with daily function. Your prescriber may adjust your dose, review your hydration and food intake, or discuss whether continuing is appropriate. Both medications require ongoing clinical oversight — you cannot simply stop and restart. Use our free GLP-1 weight loss calculator to explore how either medication might fit your health profile, and discuss results with your healthcare team.
- 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 more common on Mounjaro or Wegovy?
Clinical trials show dizziness occurs with both, but at similar modest rates. SURMOUNT-1 and STEP-1 data do not establish clear superiority. Individual experience varies significantly based on dose, tolerance, hydration, and personal metabolism. Your prescriber assesses which suits you best following clinical assessment.
Does dizziness go away on Mounjaro or Wegovy?
For most users, mild dizziness improves within 4–8 weeks as the body adapts. Staying hydrated, eating regular small meals, and rising slowly from sitting or lying down helps. If dizziness persists beyond 8 weeks or worsens, contact your GP — dose adjustment or medication review may be needed.
Can I switch from Mounjaro to Wegovy if I feel dizzy?
Switching between medications should only be done under prescriber guidance. Switching is possible but requires a clinical plan — you cannot simply stop one and start another. Discuss dizziness with your prescriber; often dose reduction or lifestyle adjustment resolves the issue without switching.
What's the difference between Mounjaro and Wegovy for side effects?
Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is GLP-1 only. This mechanistic difference may influence how individuals tolerate side effects overall. Mounjaro doses are higher (up to 15 mg weekly vs Wegovy's 2.4 mg), but both start low and titrate gradually to minimise early side effects like dizziness.
Should I tell my GP about dizziness before starting either medication?
Yes. Inform your prescriber of any existing dizziness, balance problems, blood pressure conditions, or medications affecting blood sugar or blood pressure. This context helps your prescriber choose the safest option for you and monitor you appropriately during treatment.
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.