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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Reducing Your Mounjaro Dose to Manage Side Effects
If you're experiencing side effects from Mounjaro (tirzepatide), reducing your dose may help. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist that works by regulating appetite and blood sugar control. While clinical trials showed it can support weight loss, side effects like nausea, vomiting, and constipation are common, particularly during dose escalation. The good news is that dose adjustment is a normal part of treatment, and your prescriber can help you find a tolerable level. This guide explains how dose reduction works, what to expect, and when to seek medical advice.
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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 Dose Adjustment Works
Mounjaro is typically started at 2.5 mg once weekly, with doses increasing every 4 weeks (5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg). Each person tolerates these doses differently. If side effects become difficult to manage, your prescriber may recommend pausing at your current dose longer than 4 weeks, reducing to a previous dose, or spacing doses further apart (though doses are normally once weekly).
Clinical evidence shows that even lower doses of tirzepatide — around 5–10 mg — can still provide meaningful weight loss support (approximately 15–19% body weight on average in trials). You don't need to reach the maximum 15 mg dose for the medication to be effective. Your prescriber will balance efficacy with tolerability to find your optimal dose.
- Common dose adjustments: holding at 2.5 mg or 5 mg longer; stepping back from 10 mg to 7.5 mg
- Not a failure: dose reduction is standard practice, not a sign the medication isn't working
- Individual variation: genetics, metabolism, and gut sensitivity all affect tolerance
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.
Managing Side Effects at Your Current Dose
Before reducing your dose, some side effects may improve with lifestyle adjustments. Nausea often decreases if you eat smaller, more frequent meals and avoid greasy or spicy foods. Dehydration can worsen nausea and constipation — drinking plenty of water and taking regular small sips throughout the day helps. For constipation, increase fibre intake gradually, move more, and consider a stool softener if advised by your GP.
Always discuss side effects with your prescriber before making any changes. They'll review how long you've been on each dose (side effects often improve after 1–2 weeks), assess the severity, and decide whether dose reduction, lifestyle changes, or both are appropriate. Use our free GLP-1 weight loss calculator to understand projected outcomes at different doses, and track your progress with our free progress tracker to monitor both weight loss and side effect patterns.
- 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 reduce my Mounjaro dose myself?
No. Mounjaro is prescription-only, and any dose change must be approved and managed by your prescriber. Contact your prescriber immediately if you're experiencing severe side effects rather than adjusting your dose independently. They can assess whether dose reduction is appropriate, whether lifestyle changes might help, or whether a switch to another medication is better.
How long does it take for Mounjaro side effects to improve after reducing my dose?
Most people notice improvement within 1–2 weeks of dose reduction, though this varies. Some side effects like nausea may decrease within days; others like hair loss take longer to resolve. If side effects persist after 2–3 weeks at a lower dose, discuss this with your prescriber — further adjustment or investigation may be needed.
Will I still lose weight on a lower Mounjaro dose?
Yes. Clinical trials show that even doses as low as 5 mg can support weight loss of around 15% of body weight on average. Weight loss at lower doses is typically slower and may plateau at a different level than higher doses, but meaningful results are still possible, especially combined with diet and physical activity.
What's the difference between pausing my dose and reducing it?
Pausing means staying at your current dose for longer than the standard 4 weeks before increasing — you don't go backwards. Reducing means going back to a previous, lower dose (e.g., from 10 mg to 7.5 mg). Your prescriber will recommend whichever is more appropriate based on your side effects and weight loss progress.
Should I try Wegovy instead if I can't tolerate Mounjaro?
Possibly. Wegovy (semaglutide) is a single GLP-1 agonist (Mounjaro is a dual GIP plus GLP-1 agonist). Some people find one more tolerable than the other. However, switching medications is a decision for your prescriber. They'll assess whether a dose reduction of Mounjaro first might work, or whether a different medication is more appropriate for you.
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.