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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Dizziness With Mounjaro vs Wegovy — What's the Difference?
Dizziness is reported by some people using Mounjaro (tirzepatide), though it's not listed as a common side effect. Wegovy (semaglutide) can also cause dizziness in some users. Both are prescription-only GLP-1 and GIP/GLP-1 receptor agonist medications used for weight management in the UK. Understanding how these medicines work differently, what clinical trials showed, and which might suit you better requires a direct conversation with your GP or a licensed prescriber who can assess your individual health profile and medical history.
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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.
How Mounjaro and Wegovy Differ in Mechanism and Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways, which is what sets it apart from other weight loss injections. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single pathway. This difference in mechanism may influence how side effects develop in individual users.
In the SURMOUNT-1 clinical trial, dizziness was reported but not as a very common side effect with Mounjaro. In the STEP-1 trial for Wegovy, dizziness was similarly uncommon. Both medicines slow gastric emptying (how quickly food leaves the stomach), which can cause nausea, dizziness, and fatigue — particularly during dose titration when you're escalating doses every 4 weeks. Mounjaro doses range from 2.5 mg to 15 mg weekly; Wegovy doses range from 0.25 mg to 2.4 mg weekly. Individual tolerance varies significantly, and dizziness may resolve as your body adjusts.
- Mounjaro: dual mechanism, once-weekly, UK prescription required
- Wegovy: single GLP-1 mechanism, once-weekly, UK prescription required
- Both require clinical assessment before prescribing
- Both can cause dizziness in some users — individual risk varies
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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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Dizziness and Prescriber Suitability — Which Medicine Is Right for You?
Neither Mounjaro nor Wegovy is universally "better" for dizziness — individual suitability depends on your personal health history, other medications, and how your body responds. If you experience dizziness with one medicine, your prescriber may suggest switching to the other, adjusting your dose schedule, taking it at a different time of day, or managing symptoms with lifestyle adjustments like staying hydrated and eating small, balanced meals.
Both medicines are licensed for UK adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds due to increased health risk at these weights. Your GP or a licensed prescriber will assess whether either medicine is safe for you, considering your full medical history, current medications (especially oral contraceptives, which may have reduced absorption), and whether you have a history of pancreatitis, gallbladder problems, or thyroid cancer.
- Prescriber assessment determines suitability — not all patients are eligible
- Dizziness may reduce over time as your body adjusts
- Lifestyle support (hydration, meal timing) can help manage symptoms
- 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.
Does Mounjaro cause more dizziness than Wegovy?
Clinical trial data does not show Mounjaro causing significantly more dizziness than Wegovy. Both medicines can cause dizziness in some users, particularly during dose escalation. Individual responses vary based on personal metabolism, other medications, and overall health. Your prescriber can advise on which is more suitable for you.
Is dizziness a common side effect of Mounjaro?
Dizziness is not listed as a "very common" or "common" side effect of Mounjaro in UK clinical data. It occurs in some users but is not the norm. Other more frequent side effects include nausea, diarrhoea, and constipation. If you experience dizziness, report it to your GP or prescriber immediately.
What should I do if I feel dizzy while taking Mounjaro?
Stay hydrated, eat regular small meals, and avoid standing up too quickly. If dizziness persists or worsens, contact your GP or prescriber. Do not stop taking Mounjaro without medical advice. They may adjust your dose, suggest timing changes, or switch you to an alternative medication if appropriate.
Can I switch from Mounjaro to Wegovy if I get dizziness?
Only your prescriber can recommend switching medications. Mounjaro and Wegovy work differently (dual vs single mechanism), so a switch is possible but must be clinically managed. Your prescriber will assess whether the switch is safe and how to manage the transition, as discontinuing one and starting another requires careful timing.
What UK prescribers should I discuss dizziness with?
Report dizziness to your GP, NHS specialist weight management service, or the online prescriber who issued your prescription. They can review your symptoms, check for other causes, adjust your dose, or recommend alternatives. Never adjust or stop your medication without professional guidance.
Ready to take control of your weight loss journey?
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