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 Shivers — Is This a Known Side Effect?
Shivers or chills are not listed as a common side effect of Mounjaro (tirzepatide) in UK clinical trials or the official prescribing information. However, they can occasionally occur alongside other symptoms like nausea, fatigue, or flu-like sensations, particularly during dose escalation. If you're experiencing shivers on Mounjaro, it's important to understand whether this is related to the medication itself, another health condition, or a temporary adjustment response. Always report any new or persistent symptoms to your GP or prescriber for proper assessment.
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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.
Mounjaro Side Effects and Shivers
Shivers are not a documented common side effect of Mounjaro, but they can occasionally occur in the context of other recognised responses. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist used for weight management in UK adults. The most frequently reported side effects include nausea, diarrhoea, vomiting, and stomach pain—particularly during the initial weeks and dose titration phases.
Some people report feeling cold, chills, or shivers alongside fatigue when starting Mounjaro or increasing their dose. This may be due to:
- General flu-like symptoms in the first few days after injection
- Dehydration from gastrointestinal side effects like diarrhoea
- Changes in appetite suppression affecting calorie intake
- Natural temperature regulation shifts as your body adjusts to the medication
These symptoms typically settle within a few days. If shivers persist or are accompanied by fever, severe chills, or other concerning signs, contact your GP immediately—this could indicate an infection or other health issue unrelated to Mounjaro.
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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
Contact your GP or NHS 111 if shivers are accompanied by fever, severe chills lasting more than 24 hours, chest pain, difficulty breathing, or signs of infection. You should also reach out to your prescriber if shivers are severe, persistent beyond a few days, or preventing you from managing your daily life.
Keep a brief record of when shivers occur, how long they last, what dose you're on, and any other symptoms present—this information helps your GP assess whether the shivers are related to Mounjaro or another cause. Remember that Mounjaro is prescription-only and requires ongoing clinical monitoring. Your prescriber is the best source for personalised advice about your individual response to the medication and whether dose adjustments might help. Using our free BMI calculator and GLP-1 weight loss calculator can help you track your overall progress and discuss outcomes with your healthcare team.
- 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.
Are shivers a common side effect of Mounjaro in the UK?
No, shivers are not listed as a common side effect of Mounjaro in UK clinical trials or prescribing information. However, they can occasionally occur alongside other symptoms like fatigue or nausea, particularly during dose escalation or in the first few days after injection. If shivers persist or worsen, contact your GP.
Could shivers be caused by something other than Mounjaro?
Yes, absolutely. Shivers can result from dehydration, infection, low blood sugar, or other unrelated health conditions. If you're experiencing shivers on Mounjaro, your GP can assess whether they're related to the medication or another cause. Always report new symptoms to your healthcare provider.
What should I do if I develop shivers after my Mounjaro injection?
If shivers are mild and last only a few hours, they may settle naturally as your body adjusts. Stay hydrated and rest. However, if shivers are severe, persistent, or accompanied by fever or chills, contact your GP or NHS 111 for assessment. Do not stop taking Mounjaro without medical advice.
How does Mounjaro dose titration affect side effects like shivers?
Mounjaro is given at gradually increasing doses (2.5 mg to 15 mg over weeks) to minimise side effects. Some people report flu-like symptoms including chills during dose escalation, which typically improve within days. Your prescriber can discuss any concerning symptoms and adjust your dose plan if needed.
Is Mounjaro available on the NHS for weight management in the UK?
Yes, Mounjaro (tirzepatide) is NICE-approved for NHS use in specialist tier 3 weight management services. NHS availability varies by region and waiting times can be lengthy. Private prescribing through a UK-licensed prescriber is also available. Either way, Mounjaro is prescription-only and requires clinical assessment before being prescribed.
Ready to take control of your weight loss journey?
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