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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Feeling Cold On Mounjaro — What You Need To Know
Some people taking Mounjaro (tirzepatide) report feeling unusually cold, particularly during the dose titration phase when starting or increasing doses. This isn't a listed common side effect in the official product information, but it's a recognised experience reported by patients in the UK. Cold sensitivity may relate to changes in metabolism and appetite suppression as your body adjusts to the medication. If you're experiencing persistent cold feelings whilst on Mounjaro, it's important to understand what might be causing it and when to contact your GP.
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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.
Why Mounjaro Might Make You Feel Cold
Feeling cold on Mounjaro isn't officially listed as a very common or common side effect, but it can occur for several interconnected reasons:
- Reduced calorie intake: When Mounjaro suppresses appetite, you eat fewer calories. Your body generates heat partly through digestion and normal metabolism — eating significantly less means your body produces less metabolic heat.
- Metabolic changes: As you lose weight, your body composition changes. Muscle tissue generates more heat than fat tissue, so gradual weight management can temporarily affect thermoregulation.
- Dose adjustment period: Cold sensitivity is most commonly reported during the first 4–8 weeks on a new dose or when escalating through the dose titration schedule (from 2.5 mg to 5 mg, 7.5 mg, and beyond).
- Blood sugar and hormonal effects: GIP and GLP-1 receptor agonists like tirzepatide affect multiple hormone pathways, which can influence how your body regulates temperature.
It's important to note that individual responses vary significantly — many people taking Mounjaro don't experience cold sensitivity at all.
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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.
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When To Contact Your GP & How To Stay Warm
Persistent or severe cold feelings that affect your daily life should be discussed with your GP, especially if accompanied by other symptoms like excessive fatigue, muscle weakness, or changes in heart rate. In the meantime, practical steps can help: wear layers, increase physical activity (which generates heat and supports weight loss), ensure you're eating nutritionally dense meals even if portions are smaller, stay hydrated, and avoid very cold environments where possible.
If you're taking other medications alongside Mounjaro — such as blood pressure medication — your prescriber may need to review your treatment, as some medications can affect temperature sensitivity. Using our free GLP-1 weight loss calculator can help you track your dose and progress, making it easier to note when cold sensitivity started and whether it correlates with dose changes.
Cold sensitivity on Mounjaro is typically temporary and improves as your body adjusts to the medication and your weight stabilises. Most people find that the symptom resolves within a few weeks of reaching a stable dose. Ensure you're getting enough protein and micronutrients — deficiencies in iron, B vitamins, or calories can worsen cold sensitivity. If cold feelings persist beyond 8 weeks on a stable dose, or if they're severe, contact your GP. Never stop taking Mounjaro without medical guidance, but do discuss any concerning symptoms with your prescriber to ensure the medication remains appropriate for you.
- 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 common side effect of Mounjaro?
Feeling cold isn't listed as a very common or common side effect in the official product information for Mounjaro (tirzepatide). However, it is reported by some patients, particularly during dose titration or when eating significantly less due to appetite suppression. Individual responses vary widely.
Why does reduced eating make you feel cold?
Food intake generates heat through digestion (thermogenesis). When you eat fewer calories due to appetite suppression, your body produces less metabolic heat. Additionally, lower calorie intake can reduce your basal metabolic rate temporarily, affecting temperature regulation.
Will feeling cold go away once I reach my maintenance dose?
In most cases, yes. Cold sensitivity is most common during the dose titration phase and often improves within 2–4 weeks of reaching a stable maintenance dose. This is because your body adjusts to the medication and your calorie intake stabilises at a sustainable level.
Should I contact my GP about feeling cold on Mounjaro?
Contact your GP if cold sensitivity is severe, persistent beyond 8 weeks on a stable dose, or accompanied by other symptoms like extreme fatigue or unusual heart rate changes. Mention all your symptoms so your prescriber can assess whether the medication remains appropriate for you.
Can I take anything to help with cold sensitivity whilst on Mounjaro?
Practical steps include wearing layers, increasing physical activity, eating nutritionally dense meals even if portions are smaller, staying hydrated, and avoiding very cold environments. Ensure adequate protein and micronutrient intake. Never add new supplements or medications without discussing with your GP or prescriber first.
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