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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Mounjaro Lightheadedness — Side Effects & UK Access
Lightheadedness is a reported side effect some people experience when taking Mounjaro (tirzepatide) in the UK. This dizziness typically occurs during the dose titration phase and often improves as your body adjusts to the medication. Understanding what causes it, how to manage it, and how to access Mounjaro through NHS or private prescription can help you make informed decisions about weight management treatment. Our free GLP-1 weight loss calculator can also help you understand potential outcomes with this medication.
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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 Lightheadedness Occurs with Mounjaro — Causes & Management
Lightheadedness with Mounjaro (tirzepatide) can occur for several reasons. The medication slows how quickly food leaves your stomach, which may temporarily affect blood sugar regulation and blood pressure. gradual weight management in early weeks can also contribute to dizziness. Additionally, reduced appetite and lower calorie intake mean some people consume fewer nutrients, leading to temporary dizziness. In clinical trials, lightheadedness affected a small percentage of users and was most common during dose titration — when your body adjusts to each new dose.
- Lightheadedness often decreases after 4–8 weeks as your body adapts
- Staying hydrated and eating balanced meals can help minimise symptoms
- Rising slowly from sitting or lying down reduces dizziness risk
- Contact your GP or prescriber if dizziness persists beyond initial adjustment periods
- Severe or worsening lightheadedness requires urgent medical attention
Your prescriber assesses your individual health before Mounjaro is prescribed and monitors you during treatment to manage any side effects effectively.
Clinically BackedWeight Loss
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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.
Accessing Mounjaro in the UK — NHS vs Private Routes & Costs
NHS access: Mounjaro is available through NICE-approved NHS specialist weight management services (tier 3/4). Referral from your GP is required, and availability varies significantly by region. Waiting lists can be lengthy in many areas.
Private access: You can obtain a Mounjaro prescription privately through online consultations with UK-licensed prescribers, without NHS referral. Private costs typically range from £129–£320 per month depending on your dose. Mounjaro doses range from 2.5mg to 15mg weekly, with higher doses generally costing more. An online clinical assessment ensures the medication is appropriate for your health profile. Use our BMI calculator to check your eligibility — adults with a BMI of 30 or above, or 27+ with weight-related health conditions, may qualify.
- 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 lightheadedness a common side effect of Mounjaro in the UK?
Lightheadedness is reported but not extremely common. In clinical trials, dizziness affected a small percentage of users. It typically occurs during dose titration and often improves as your body adjusts. Always inform your prescriber if dizziness persists beyond the initial adjustment period.
How can I reduce lightheadedness when taking Mounjaro?
Stay well hydrated, eat regular balanced meals despite reduced appetite, rise slowly from sitting or lying down, and avoid standing for long periods without movement. Many people find symptoms reduce significantly after 4–8 weeks. Your prescriber can also adjust your dose schedule if needed.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is available through NICE-approved NHS specialist weight management services. You'll need a GP referral to tier 3/4 services. Availability and waiting times vary considerably by region and local ICB commissioning decisions.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose and provider. Doses start at 2.5mg and escalate weekly up to a maximum of 15mg. An online clinical assessment with a UK-licensed prescriber is required before prescription.
Should I stop taking Mounjaro if I experience lightheadedness?
Do not stop without consulting your prescriber. Mild lightheadedness often improves with time and self-care adjustments. However, contact your GP immediately if dizziness is severe, persistent, or accompanied by other symptoms like chest pain or fainting.
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.