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 and Feeling Cold — What You Need to Know
Feeling unusually cold whilst taking Mounjaro is not listed as a common or very common side effect in the official medicine information, but some people report feeling cold during tirzepatide treatment. This can happen for several reasons related to how the medication works and changes to your metabolism. If you're experiencing persistent coldness, it's worth understanding what might be causing it and when to speak to your GP or prescriber.
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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.
Why Mounjaro Might Make You Feel Cold
Feeling cold on Mounjaro may be linked to several factors. First, gradual weight management itself can lower body temperature — as you lose weight, you have less insulating body fat, which can make you feel colder, especially in your extremities. Second, Mounjaro slows your metabolic rate as your body adapts to lower calorie intake and reduced appetite. A slower metabolism generates less internal heat, which some people experience as feeling chilly.
- Weight loss reduces natural insulation from body fat
- Reduced food intake can lower metabolic heat production
- Changes to blood circulation during gradual weight management may contribute
- Individual sensitivity to cold varies significantly
Additionally, if you're eating significantly fewer calories on Mounjaro, your body has less fuel to generate warmth through thermogenesis — the process of burning calories to produce heat. This is a normal physiological response, not a direct side effect of the tirzepatide molecule itself.
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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 Speak to Your GP or Prescriber
Mild coldness that improves with warmer clothing is usually not a cause for concern and typically lessens as your body adapts over weeks. However, contact your GP or the prescriber who issued your Mounjaro KwikPen if you experience:
- Severe or persistent shivering that doesn't improve with extra layers
- Coldness accompanied by unusual fatigue or weakness
- Feeling cold alongside other concerning symptoms like chest pain or shortness of breath
- Signs of hypothermia (extreme confusion, slurred speech, or loss of coordination)
Your prescriber can assess whether the symptom is related to your dose, your overall calorie intake, or another factor, and advise on whether you should adjust your diet, clothing, or medication approach.
- 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.
Is feeling cold a listed side effect of Mounjaro?
Feeling cold is not listed as a common or very common side effect in the official product information for Mounjaro (tirzepatide). However, some people report it during treatment, likely due to weight loss itself and metabolic changes rather than a direct side effect of the medication. If you're concerned, discuss it with your prescriber.
Why does gradual weight management make you feel cold?
When you lose weight, you have less body fat to provide insulation, making you feel colder — especially in your hands and feet. Additionally, a reduced calorie intake lowers your metabolic rate, meaning your body generates less heat. These are normal physiological responses to weight loss.
Can I reduce feeling cold whilst taking Mounjaro?
Yes. Wear extra layers, increase slightly warmer clothing, drink warm beverages, and ensure you're eating enough calories for your activity level. If your calorie intake is too low, your prescriber may recommend increasing it slightly. Gentle exercise can also help maintain body temperature.
Is feeling cold dangerous?
Mild coldness is not dangerous and typically improves as your body adapts. However, signs of severe hypothermia — such as extreme confusion, uncontrollable shivering, or loss of coordination — require immediate medical attention. Seek help from A&E if these occur.
Should I stop Mounjaro if I'm feeling cold?
Do not stop Mounjaro without speaking to your prescriber first. Coldness alone is not a reason to discontinue treatment. Discuss the symptom with your GP or prescriber, who can assess whether it's related to your dose, calorie intake, or other factors and advise on next steps.
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.