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 Runny Nose vs Wegovy: Side Effect Comparison
Runny nose is not listed as a common side effect of either Mounjaro or Wegovy in UK clinical trials, though both medications can cause upper respiratory symptoms. If you're considering GLP-1 or dual GIP/GLP-1 weight loss treatment, understanding how Mounjaro (tirzepatide) and Wegovy (semaglutide) compare is important. Both are prescription-only injectables licensed in the UK, but they work differently and their side effect profiles vary. This guide explains the key differences to help you understand what a prescriber might consider when assessing your individual suitability.
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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.
How Mounjaro and Wegovy Differ in Mechanism and Side Effects
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways. Wegovy (semaglutide) is a GLP-1-only agonist. This difference affects both how they work and their side effect profiles. In the SURMOUNT clinical trials, Mounjaro showed a higher rate of gastrointestinal side effects (nausea, vomiting, diarrhoea) compared to Wegovy in the STEP trials, though both are generally well-tolerated at therapeutic doses. Respiratory symptoms like runny nose are uncommon with both medications. Upper respiratory tract infections do occur in clinical trials, but these are typically short-lived and not significantly higher than placebo. The choice between them depends on individual health factors, not which causes fewer nasal symptoms specifically. Your prescriber will assess which is more appropriate for you based on your medical history, current medications, and weight loss goals.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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Which Medication Might Suit You Better?
Neither Mounjaro nor Wegovy is objectively "better" — suitability is entirely individual. Some people respond better to the dual action of Mounjaro; others prefer Wegovy's simpler mechanism. If you have a family history of gallbladder problems, certain diabetic complications, or are taking oral contraceptives, your GP or prescriber may recommend one over the other. Both require a clinical assessment before prescription through either NHS specialist weight management services or private online prescribing. Use our GLP-1 weight loss calculator to explore projected outcomes at different doses, and discuss specific concerns about side effects with your prescriber. Your medical history, not the runny nose question alone, should guide the decision.
- 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 runny nose a known side effect of Mounjaro in the UK?
Runny nose is not listed as a common side effect of Mounjaro in UK product information. Upper respiratory tract infections have occurred in clinical trials but are rare and typically mild. If you develop a persistent runny nose after starting Mounjaro, discuss it with your GP to rule out other causes.
Does Wegovy cause runny nose more than Mounjaro?
No. Runny nose is not a documented side effect of either medication. Both can occasionally cause upper respiratory symptoms, but these are uncommon and not significantly different between them. Most nasal congestion during weight loss treatment is unrelated to the medication itself.
What are the most common side effects of Mounjaro vs Wegovy?
Both share similar gastrointestinal side effects: nausea, diarrhoea, vomiting, and constipation are most common. Mounjaro, as a dual-action medication, shows slightly higher rates of nausea in trials. These typically improve as your body adjusts. Serious side effects like pancreatitis are rare with both.
Can I switch from Mounjaro to Wegovy if I get respiratory symptoms?
If you experience genuine side effects with one medication, a prescriber may consider switching to the other. However, respiratory symptoms like runny nose are unlikely to be caused by either medication. Your GP should investigate other causes first — allergies, infection, or environmental factors are more common culprits.
How do I know which medication will suit me better?
A UK prescriber will assess your medical history, current medications, weight, BMI, and any existing health conditions to recommend the most appropriate option. Neither choice depends on runny nose risk. Both Mounjaro and Wegovy require a prescription following a clinical assessment — your prescriber's recommendation is based on your individual health profile, not on side effect fears.
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