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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What to Do If You Take an Extra Dose of Mounjaro
Taking an accidental extra dose of Mounjaro (tirzepatide) is a concern many UK patients have. If this happens, it's important to understand what to do next and when to seek medical advice. This guide covers NHS safety guidance, what an extra dose means for your body, and when to contact your GP or NHS 111. Mounjaro is a prescription-only weight management injection with carefully prescribed doses, so understanding dose safety is essential for anyone using this medication in the UK.
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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.
Understanding Mounjaro Dosing and Extra Doses
Mounjaro is prescribed in specific weekly doses that escalate gradually: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg as the maximum dose. Each dose is delivered via a Mounjaro KwikPen containing exactly one week's injection. The prescribing schedule means each dose increase allows your body time to adjust before moving to the next level.
If you accidentally take an extra dose by injecting twice in one week, or using a higher dose than prescribed, your body receives a larger amount of the active ingredient tirzepatide than planned. This may intensify side effects temporarily but is not typically life-threatening. However, this is why it's crucial to contact your GP or NHS 111 immediately for guidance specific to your situation. Never attempt to compensate by skipping the next dose — always seek professional advice on how to continue safely.
- Contact NHS 111 or your GP immediately if you take an extra dose
- Have your prescription details and the dose you took ready to discuss
- Do not skip your next scheduled dose without medical guidance
- Document the extra dose in case you need to discuss it at future appointments
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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 Seek Medical Advice and What to Expect
If you've taken an extra dose of Mounjaro, you should seek medical advice promptly. Call NHS 111 (available 24/7 across the UK) or contact your GP surgery during business hours. A healthcare professional can assess your individual situation, review your medical history, and advise whether you need to be seen in person or monitored at home.
An extra dose may cause temporary worsening of common side effects including nausea, vomiting, diarrhoea, or stomach pain. These symptoms typically resolve within a few days but should be reported to your GP if they're severe or prolonged. Your prescriber may also adjust your next dose or schedule depending on your response. Always keep your prescription information and KwikPen with you so you can reference exact doses with healthcare professionals.
- 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.
What should I do immediately if I've accidentally injected twice in one week?
Contact NHS 111 immediately or call your GP surgery. Have your KwikPen and prescription details available. A healthcare professional will assess your situation and advise on next steps. Do not skip your next scheduled dose without medical guidance — always follow professional advice.
Will an extra dose of Mounjaro cause serious harm?
An accidental extra dose is unlikely to be life-threatening, but it may intensify side effects like nausea and stomach pain temporarily. However, you should still contact your GP or NHS 111 for personalised advice, as risks and management depend on your individual health, other medications, and the dose involved.
Can I skip my next dose of Mounjaro if I took an extra one?
No — never skip a dose without medical guidance. Your prescriber needs to know about the extra dose and will advise on whether to adjust your next injection date or dose. Always contact your GP or NHS 111 before making any changes to your Mounjaro schedule.
How do I avoid accidentally taking an extra dose of Mounjaro?
Mark your injection date clearly on a calendar, store your KwikPens in a clearly labelled container, and set a phone reminder for your injection day. If you're unsure whether you've injected that week, contact your GP or NHS 111 rather than guessing — it's safer to check than risk an accidental double dose.
What side effects might worsen if I take an extra dose?
The most common side effects — nausea, diarrhoea, vomiting, and stomach pain — may be more intense after an extra dose. These typically settle within a few days. If side effects are severe, persistent, or if you develop signs of pancreatitis (severe stomach pain spreading to your back), seek urgent medical attention via NHS 111 or A&E.
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.