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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Does Mounjaro Make You Feel Cold?
Feeling cold is a less commonly reported side effect of Mounjaro (tirzepatide), the prescription-only weight management injection licensed in the UK. While nausea and digestive changes are more frequent, some people do experience chills or sensitivity to cold temperatures during treatment. This guide explains why this happens, how common it is, and what NHS guidance suggests about managing it safely.
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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 May Cause Feeling Cold
The exact mechanism behind cold sensitivity with Mounjaro isn't fully understood, but several factors may contribute. gradual weight management itself can reduce your body's insulating layer of fat, making you feel colder more easily—this is particularly noticeable in the first 8–12 weeks as your body adjusts. Mounjaro's dual GIP and GLP-1 receptor agonist action may also affect your metabolic rate and how your body regulates temperature.
- Weight loss reduces natural insulation, increasing cold sensitivity
- Changes in metabolic rate during early dose titration (weeks 1–16) may affect thermoregulation
- Reduced appetite can lower energy intake, which your body uses to generate heat
- Dehydration from nausea or diarrhoea may increase feelings of cold
This side effect is temporary for most people and typically lessens as your body acclimates to the medication and your weight stabilises.
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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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Managing Cold Sensitivity and When to Contact Your GP
If you're feeling cold while taking Mounjaro, practical steps include wearing layers, staying hydrated (aim for 6–8 glasses of water daily), and ensuring you're eating enough protein and calories to support your weight loss safely. Most people find this sensation reduces after 4–8 weeks on a stable dose. However, contact your GP if: you experience persistent, severe chills; you develop a fever alongside feeling cold; or the sensation doesn't improve after 8 weeks. Your prescriber may adjust your dose titration or check for other causes. This is one reason why NHS tier 3 specialist weight management services provide ongoing support during Mounjaro treatment.
Remember that feeling cold is not dangerous in itself, but it's important to monitor your overall wellbeing during treatment. Use our free GLP-1 weight loss calculator to understand what to expect during your weight loss journey, and our BMI calculator to track how your body composition changes as you progress. Keep a symptom diary and share it with your prescriber at your next review—this helps them understand whether dose adjustments are needed.
- 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 is not listed as a "very common" or "common" side effect in clinical trials, but some users report it. It's more likely during gradual weight management in the first 8–12 weeks. If you experience it, mention it to your GP—it's worth monitoring but usually temporary.
Will feeling cold go away once I'm on a stable Mounjaro dose?
Yes, for most people. Cold sensitivity typically peaks during dose titration (weeks 1–16) and improves once your body adapts and weight loss stabilises. If it persists after 8 weeks on your maintenance dose, contact your prescriber.
What's the difference between Mounjaro and Wegovy regarding side effects?
Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is a GLP-1 agonist only. Both can cause cold sensitivity during weight loss, though it's not a primary reported side effect. Individual experiences vary—your GP can discuss which suits you better.
Should I stop taking Mounjaro if I feel cold all the time?
No—don't stop without speaking to your GP first. Feeling cold alone isn't a reason to stop treatment. Instead, contact your prescriber to discuss whether your dose needs adjusting or whether other factors (hydration, nutrition, underlying health) need addressing.
How does NHS Mounjaro prescribing differ from private prescribing for this side effect?
Both NHS tier 3 services and private prescribers should ask about side effects and provide support. NHS services may have longer appointment gaps; private prescribers often offer quicker follow-ups. Either way, report feeling cold at your next review and keep records for your prescriber.
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