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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Feeling Light Headed on Mounjaro — What You Need to Know
Dizziness and feeling light headed are recognised side effects that some people experience when taking Mounjaro (tirzepatide). This guide explains why this happens, how to access Mounjaro safely in the UK, and what prescription costs typically look like through both NHS and private routes. If you're experiencing dizziness, always speak to your GP or prescriber before continuing treatment—they can advise whether to adjust your dose or medication plan.
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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.
Understanding Dizziness on Mounjaro and UK Prescription Costs
Feeling light headed or dizzy on Mounjaro is a recognised but less common side effect. It typically occurs during the initial weeks of treatment or when increasing your dose. The dizziness may be related to several factors: rapid blood sugar changes as your body adjusts to the medication, mild dehydration (especially if you're experiencing nausea or reduced appetite), blood pressure changes, or the medication's effect on how quickly your stomach empties food.
In the UK, prescription costs for Mounjaro vary significantly depending on whether you access it through the NHS or private prescription services. Private prescriptions typically cost between £129 and £320 per month depending on the dose you're using and the provider. A standard private prescription includes the clinical assessment by a UK-licensed prescriber, the prescription itself, and delivery of your medication from a GPhC-registered pharmacy. NHS access is available through specialist tier 3 weight management services, but availability varies greatly by region and waiting times can be lengthy. Always report dizziness to your prescriber—they may adjust your dose titration schedule or suggest practical measures like staying hydrated and eating small regular meals.
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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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NHS vs Private: How to Access Mounjaro in the UK
The NHS route involves referral to your local tier 3 specialist weight management service through your GP. Once referred and assessed, you may be prescribed Mounjaro at no cost through the NHS—but access depends entirely on your regional Integrated Care Board (ICB) and current demand. Some areas have waiting lists of six months to two years. The private route is faster: you complete an online consultation with a UK-licensed prescriber, who assesses your suitability for treatment. If approved, they issue a prescription that a GPhC-registered pharmacy dispenses and delivers. This route bypasses NHS waiting lists but requires you to cover the full cost. Many people choose private prescribing for faster access, while others prefer the NHS route if available. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to track your progress once you start treatment.
- 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.
Why do I feel light headed on Mounjaro?
Dizziness on Mounjaro can occur due to rapid blood sugar changes, dehydration from reduced appetite or nausea, blood pressure fluctuations, or slower stomach emptying. It's more common during dose titration. Always report persistent dizziness to your prescriber—they may adjust your dose schedule or recommend practical measures like increasing fluid intake and eating small meals regularly.
How much does Mounjaro cost on private prescription in the UK?
Private Mounjaro prescriptions typically range from £129 to £320 per month depending on your dose (2.5 mg to 15 mg). This includes the online clinical assessment, prescription, and delivery from a GPhC-registered pharmacy. Costs may vary between providers. NHS access is free but involves waiting times that vary significantly by region.
What's the difference between NHS and private Mounjaro access?
NHS access is through specialist tier 3 weight management services following a GP referral—it's free but has variable waiting times. Private prescribing is faster (usually within days) and doesn't require NHS referral, but you pay the full cost. Both routes require a clinical assessment and prescription from a UK-licensed prescriber.
Should I stop Mounjaro if I feel dizzy?
Don't stop suddenly without medical advice. Contact your GP or prescriber immediately to report dizziness. They may adjust your dose titration, suggest staying hydrated and eating small meals, or temporarily pause treatment. Never change your dosing schedule without guidance from your healthcare provider.
How long does dizziness last when starting Mounjaro?
Mild dizziness often improves within the first few weeks as your body adjusts to the medication. If it persists beyond your initial dose period or worsens when you increase doses, speak to your prescriber. Staying well hydrated and eating regular small meals can help reduce dizziness during the adjustment phase.
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.