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 and Asthma: What's the Connection?
If you have asthma and are considering Mounjaro (tirzepatide) for weight management, it's natural to wonder whether this prescription injection could affect your respiratory health. The good news is that asthma is not listed as a contraindication to Mounjaro, meaning people with asthma can potentially use it. However, there are important considerations your GP needs to know, and your asthma should be well-controlled before starting any weight loss medication. This guide explains what the evidence shows and what to discuss with your prescriber.
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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 Mounjaro Works and Respiratory Health
Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways to help regulate appetite and blood sugar control. Unlike some weight loss medications, tirzepatide does not directly affect the airways or lungs. The medication works in the stomach and brain to slow gastric emptying, reduce hunger signals, and support feeling fuller after smaller meals.
That said, any medication that causes nausea, vomiting, or changes to eating patterns could theoretically affect asthma control indirectly. For example, severe nausea or dehydration might trigger asthma symptoms in some people. Additionally, gradual weight management itself can sometimes improve asthma control in overweight or obese individuals — weight loss may reduce inflammation and airway pressure, making breathing easier. Your GP will assess your individual asthma history and current control before prescribing Mounjaro.
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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.
What Your GP or Prescriber Needs to Know
Before starting Mounjaro, you must inform your prescriber that you have asthma. Key details to share include: whether your asthma is well-controlled, what medications you take for it (inhalers, corticosteroids, biologics), how often you have symptoms, and whether you've had any recent asthma attacks or hospital admissions. If your asthma is poorly controlled, your prescriber may recommend stabilising it first before starting weight loss medication.
The UK GPhC-registered prescriber conducting your clinical assessment will review all your medical conditions. If you're accessing Mounjaro through an NHS specialist weight management service, they will have your full GP records. Using the GLP-1 weight loss calculator on this page can help you understand potential outcomes, but your prescriber's individual assessment is what matters for safety.
- 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.
Can I take Mounjaro if I have asthma?
Asthma alone is not a reason to avoid Mounjaro, but your asthma must be well-controlled. Your prescriber will assess your asthma history and current control during your clinical assessment. If your asthma is unstable or poorly managed, discuss this with your GP before requesting Mounjaro. Tell your prescriber exactly which asthma medications you take.
Could Mounjaro trigger an asthma attack?
Mounjaro does not directly affect airways, but common side effects like nausea or vomiting could theoretically trigger asthma symptoms in some people if severe. Most people experience mild nausea that improves over time. If you notice your asthma worsens after starting Mounjaro, contact your GP or asthma nurse immediately.
Will weight loss from Mounjaro help my asthma?
Yes, evidence suggests that even modest weight loss (5–10% of body weight) can improve asthma control in overweight or obese people. Weight loss reduces airway inflammation and chest wall pressure, making breathing easier. Many people find their asthma symptoms improve alongside weight loss.
Should I stop my asthma inhalers when taking Mounjaro?
No. Never stop asthma medications without advice from your GP or asthma nurse. Continue taking your preventer and reliever inhalers as prescribed. Your prescriber and asthma care team can monitor whether doses need adjusting as your weight changes.
Is Mounjaro safe if I take oral corticosteroids for asthma?
Mounjaro may affect how oral medications are absorbed because it slows gastric emptying. If you take oral corticosteroids or other oral asthma medications, inform your prescriber. You may need to take oral medications at a different time of day, or your doses may need review as your weight changes.
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.