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 Causes Mounjaro Shivers and Chills?
Shivers and chills are not a commonly reported side effect of Mounjaro (tirzepatide), but some people using this GLP-1 injection may experience temperature-related sensations, particularly during the dose titration phase. If you're taking Mounjaro and experiencing shivers, it's important to understand what might be causing them, when to contact your GP, and how this symptom relates to your overall treatment plan. This guide explains what you need to know about Mounjaro and temperature sensitivity in a UK health context.
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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 Shivers and Temperature Changes
Shivers and chills with Mounjaro are not listed as very common or common side effects in the official product information. However, some people taking tirzepatide report feeling unusually cold or experiencing shivering sensations, particularly when starting the medication or increasing doses.
These temperature changes may be linked to several factors: changes in how your body processes energy and fat, alterations to your metabolic rate as your appetite decreases, or your body adjusting to reduced food intake. Additionally, gastrointestinal side effects like nausea, vomiting, or diarrhoea — which are very common with Mounjaro — can dehydrate you, and dehydration can trigger chills and shivers.
- Shivers may be more noticeable during dose increases (2.5 mg to 5 mg to 10 mg, etc.)
- They typically resolve within days to weeks as your body adjusts
- Staying hydrated and eating regular, balanced meals can help manage temperature regulation
- If shivers persist or are accompanied by fever, contact your GP immediately
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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.
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When to Contact Your GP About Mounjaro Shivers
Contact your GP or call NHS 111 if you experience shivers alongside fever, severe fatigue, muscle aches, or signs of infection. These could indicate an infection rather than a medication side effect. You should also seek medical advice if shivers are severe, persistent beyond two weeks, or significantly affecting your quality of life.
If you're unsure whether your symptoms are normal, your prescriber can assess you during a follow-up consultation. Keep a symptom diary noting when shivers occur, what you were doing, room temperature, and other side effects — this helps your healthcare provider understand your individual response to Mounjaro. Never stop taking Mounjaro without medical guidance.
- 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?
Shivers are not listed as a very common or common side effect of Mounjaro in clinical trials. However, some people report feeling unusually cold or experiencing chills, especially during dose increases or when adjusting to reduced food intake. If you experience persistent shivers, contact your GP for assessment.
Why might Mounjaro cause shivers or chills?
Possible reasons include metabolic changes as your body adjusts to reduced appetite, dehydration from common GI side effects like nausea or diarrhoea, or your body's temperature regulation shifting due to lower calorie intake. Staying hydrated and maintaining regular meals can help manage these sensations.
How long do Mounjaro shivers typically last?
Temperature-related sensations usually resolve within days to weeks as your body adjusts to the medication. If shivers persist beyond two weeks or are accompanied by fever, contact your GP. Individual experiences vary, and your prescriber can provide personalised guidance.
Should I stop taking Mounjaro if I get shivers?
No — do not stop Mounjaro without medical guidance, even if you experience shivers. Contact your prescriber or GP to discuss your symptoms. They can assess whether shivers are a normal adjustment response or warrant dose adjustment or further investigation.
What's the difference between Mounjaro shivers and other side effects?
Mounjaro's most common side effects are nausea, diarrhoea, vomiting, and constipation. Shivers are less common but may occur alongside these. If shivers are accompanied by fever, persistent cough, or severe fatigue, seek urgent medical advice — these could indicate infection rather than medication response.
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