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 Mounjaro Dose Side Effects — NHS Guidance
If you're experiencing side effects from Mounjaro, dose adjustment may help. The NHS and UK prescribers use a careful titration schedule to find the right dose for you, and reducing your Mounjaro dose is a recognised approach when nausea, vomiting, or digestive issues become difficult to manage. This guide explains how dose reduction works, what to expect, and when to speak with your GP or prescriber about adjusting your tirzepatide dose.
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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 Titration and Reduction Work in the UK
Mounjaro is prescribed using a step-wise dose escalation schedule, starting at 2.5 mg and increasing every 4 weeks up to a maximum of 15 mg. However, the NHS and UK private prescribers recognise that not every patient tolerates higher doses well.
- If side effects become severe at a particular dose, your prescriber may recommend staying at that dose for longer, pausing escalation, or reducing back to a previous lower dose
- This is entirely normal and safe — finding your individual tolerance level is part of treatment
- Common reasons for dose reduction include persistent nausea, vomiting, or severe abdominal discomfort that doesn't improve within 2–3 weeks
- Weight loss on Mounjaro is dose-dependent, but you may still see meaningful results at lower doses (5 mg or 10 mg) than the maximum 15 mg
- Your GP or specialist prescriber will monitor your tolerability and adjust based on your individual response
Never stop or reduce your dose without medical guidance — always contact your prescriber first. Try our GLP-1 weight loss calculator to understand potential outcomes at different doses.
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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.
When to Ask Your GP About Dose Reduction
Contact your GP or prescriber immediately if you experience severe or persistent side effects: unbearable nausea lasting more than 3 weeks, repeated vomiting, severe abdominal pain spreading to your back (possible pancreatitis), or constipation affecting daily life.
You should also speak with your prescriber if:
- Side effects are making you unable to maintain adequate nutrition or hydration
- Gastrointestinal symptoms haven't improved after 2–3 weeks at your current dose
- You're concerned that a side effect might be dangerous or unusual for you
NHS specialist weight management services and private prescribers are trained to adjust dosing based on your tolerability. There is no "failure" in reducing your dose — it's a medical adjustment to help you stay safe and compliant with treatment.
- 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 — never adjust your dose without speaking to your prescriber first. Mounjaro dose changes must be managed medically. Contact your GP or the service prescribing your medication if you're struggling with side effects. They may recommend pausing escalation, staying at your current dose longer, or genuinely reducing to a previous lower dose.
Will reducing my Mounjaro dose mean less weight loss?
Possibly, but not necessarily. Clinical trials show weight loss is dose-dependent, but many people achieve meaningful results at 5 mg or 10 mg rather than the maximum 15 mg. Your prescriber will help find the right balance between tolerability and effectiveness for your individual situation.
How long does it take for Mounjaro side effects to improve?
Most side effects like nausea and diarrhoea improve within 1–3 weeks as your body adjusts. If they persist beyond 3 weeks at a given dose, contact your prescriber about adjustment. Some people need a slower titration schedule or a lower maintenance dose.
What's the difference between pausing dose increases and actual dose reduction?
Pausing means staying at your current dose for longer than 4 weeks before increasing again. Actual reduction means going back to a previous lower dose. Your prescriber may recommend either approach depending on your side effects and weight loss progress.
Does the NHS support dose adjustment for Mounjaro side effects?
Yes — NHS tier 3 weight management services are trained in GLP-1 and tirzepatide management and regularly adjust doses based on tolerability. Private prescribers also adjust doses routinely. Side effect management is a normal, expected part of treatment.
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.