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 Dry Mouth vs Wegovy: Which Causes More?
Dry mouth is a recognised side effect reported with both Mounjaro (tirzepatide) and Wegovy (semaglutide), though it's not listed as a very common side effect for either medication in UK clinical data. Both are prescription-only weight management injections, but they work through different mechanisms—Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy activates GLP-1 only. Side effect profiles differ slightly between the two, and how your body responds depends on individual factors, dose, and duration of treatment. Your prescriber will assess which medication suits you best.
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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) activates two hormone pathways simultaneously—GIP (glucose-dependent insulinotropic polypeptide) and GLP-1. This dual mechanism may contribute to a broader range of side effects compared to single-pathway medications. In clinical trials, gastrointestinal effects like nausea, diarrhoea, and constipation are more commonly reported than dry mouth.
Wegovy (semaglutide) targets GLP-1 only, which may result in a different side effect profile. Nausea and gastrointestinal symptoms dominate reported side effects, with dry mouth mentioned less frequently.
Neither medication lists dry mouth as a "very common" side effect in UK prescribing information, though it has been reported anecdotally by some patients. If you experience dry mouth while taking either medication, your GP or prescriber can advise whether it's related to the injection, dehydration, or another factor.
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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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Clinical Trial Data and Individual Suitability
The SURMOUNT-1 trial (Mounjaro) and STEP-1 trial (Wegovy) both measured weight loss and side effects across thousands of participants. Importantly, neither trial flagged dry mouth as a defining difference between the two medications. Side effect frequency and severity vary significantly between individuals—what affects one person may not affect another.
Your prescriber will consider your medical history, other medications, and any previous side effects you've experienced with similar treatments when deciding which medication to recommend. Both require a clinical assessment before prescription. Use our GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to understand your starting point before discussing treatment with your GP or a licensed prescriber.
- 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 dry mouth than Wegovy?
No published clinical trial data directly compares dry mouth rates between the two. Both medications report it infrequently. Individual responses vary. Dry mouth may be related to dose, dehydration, or other factors. Your prescriber can help identify the cause and recommend management strategies.
What's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 receptor agonist, while Wegovy (semaglutide) activates GLP-1 only. Mounjaro's dual mechanism may produce slightly different side effects. Average weight loss in trials is comparable, but individual results vary significantly.
How common is dry mouth with Mounjaro?
Dry mouth is not listed as a "very common" or "common" side effect of Mounjaro in UK prescribing information. If you experience it, mention it to your GP or prescriber—it may be manageable with increased water intake or other simple measures.
Is dry mouth worse at higher Mounjaro doses?
Side effects, including dry mouth, can intensify as doses increase. Mounjaro starts at 2.5 mg and escalates gradually to a maximum of 15 mg. Your prescriber monitors side effects at each dose level and adjusts your treatment accordingly.
Which medication should I choose if I'm concerned about dry mouth?
Neither Mounjaro nor Wegovy lists dry mouth as a major side effect, so choice shouldn't be based on this alone. Your prescriber will recommend the most suitable medication based on your medical history, eligibility, NHS or private access, and other health factors. Both require a clinical assessment.
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