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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Can You Decrease Mounjaro Dose in the UK?
Yes, you can decrease your Mounjaro dose in the UK, but only under the guidance of your prescriber. Dose adjustments — whether up or down — should never be made without medical supervision. If you're experiencing difficult side effects or other concerns, your GP or specialist can review your treatment and adjust your tirzepatide dose accordingly. This guide explains the NHS approach to Mounjaro dose management and what you need to know about reducing your injection.
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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 Adjustments Work in NHS Practice
Mounjaro dose adjustments follow a structured approach in the UK:
- Doses are normally increased gradually every 4 weeks, starting from 2.5 mg and moving up to a maximum of 15 mg per week
- If you experience intolerable side effects, your prescriber may hold you at your current dose for an extra week or two before escalating
- Decreasing your dose is typically only recommended if you're struggling with significant nausea, vomiting, or other serious side effects that affect daily functioning
- Your prescriber will assess whether a temporary dose reduction, pausing treatment, or switching to an alternative medication like Wegovy is most appropriate
- NHS specialists follow MHRA guidance and NICE recommendations, which do not routinely recommend deliberate dose reduction as part of standard treatment
- Any dose change should be discussed with your GP or specialist — never adjust your own Mounjaro KwikPen injections
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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 Your Prescriber Might Reduce Your Mounjaro Dose
Dose reduction is typically considered if you experience severe or persistent side effects that significantly impact your quality of life. Common reasons include uncontrolled nausea lasting more than a few weeks, repeated vomiting, severe constipation or diarrhoea, or signs of pancreatitis (severe stomach pain). Your prescriber may also recommend pausing or reducing your dose if you're struggling to tolerate food or are at risk of nutrient deficiencies. In some cases, switching to a different GLP-1 medication such as semaglutide (Wegovy) — which is administered at lower tirzepatide-equivalent doses — may be an option. Always contact your GP or specialist rather than stopping or reducing your dose yourself.
- 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 if I'm having side effects?
No. Never adjust your Mounjaro dose without speaking to your prescriber first. Side effects like nausea often improve over time as your body adjusts, typically within 2–4 weeks. Your GP or specialist can advise whether waiting longer, temporarily pausing, or reducing your dose is the right choice.
Is there an official "lower" dose of Mounjaro if the 2.5 mg starting dose is too strong?
The 2.5 mg dose is the lowest therapeutic starting dose available in the UK. If you cannot tolerate even this dose, your prescriber may suggest pausing for a week, trying a different medication, or exploring whether Wegovy (semaglutide) at a lower equivalent dose might suit you better.
What if I want to stop Mounjaro and restart at a lower dose later?
Stopping and restarting Mounjaro should only be done under medical guidance. Your prescriber needs to assess whether restarting makes sense clinically and will advise on the appropriate starting dose when you resume. Do not stop your treatment without discussing it with your GP or specialist first.
How long should I stay on a dose before deciding it's not working?
Clinical guidance recommends staying on each Mounjaro dose for at least 4 weeks to assess effectiveness and allow side effects to settle. Weight loss takes time, and your body needs time to adapt to each dose increment. Your prescriber will monitor your progress and adjust accordingly.
Can I reduce my Mounjaro dose if I'm losing weight too quickly?
If you're losing weight very rapidly or experiencing concerning symptoms, contact your prescriber immediately. gradual weight management can increase risks of gallstones and nutrient deficiencies. Your GP can assess whether a temporary pause, dose reduction, or dietary adjustment is needed to ensure safe, sustainable weight loss.
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.