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Is being cold a side effect of Mounjaro? Feeling cold whilst taking Mounjaro (tirzepatide) is not listed as an official side effect in UK regulatory guidance, yet some patients report increased sensitivity to cold during treatment. Mounjaro is a dual GIP and GLP-1 receptor agonist licensed for type 2 diabetes and weight management. Whilst cold intolerance does not appear in clinical trial data or the Summary of Product Characteristics, the substantial weight loss associated with Mounjaro may indirectly affect temperature perception through loss of insulating adipose tissue, metabolic adaptation, and reduced caloric intake. Understanding these mechanisms helps distinguish between expected physiological changes and symptoms requiring medical investigation.
Quick Answer: Feeling cold is not an official side effect of Mounjaro, but weight loss from the medication may indirectly cause cold sensitivity through loss of insulating body fat and metabolic changes.
Mounjaro (tirzepatide) is a prescription medication licensed in the UK for the treatment of type 2 diabetes mellitus and, more recently, for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with weight-related comorbidities. It belongs to a novel class of medicines known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. By mimicking these naturally occurring hormones, Mounjaro helps regulate blood glucose levels, reduces appetite, and slows gastric emptying, which collectively contribute to improved glycaemic control and significant weight loss.
The mechanism of action involves binding to both GIP and GLP-1 receptors, which stimulates insulin secretion when blood glucose is elevated, suppresses glucagon release, and promotes satiety. This dual action distinguishes tirzepatide from single GLP-1 receptor agonists and may account for its enhanced efficacy in clinical trials. Mounjaro is administered once weekly via subcutaneous injection, typically in the abdomen, thigh, or upper arm.
Common side effects reported in clinical trials and post-marketing surveillance include gastrointestinal disturbances such as nausea, vomiting, diarrhoea, constipation, and abdominal discomfort. These effects are generally most pronounced during dose escalation and often diminish over time as the body adjusts to the medication. Other frequently reported adverse effects include decreased appetite, fatigue, injection site reactions, and headache. Hypoglycaemia may occur, particularly when Mounjaro is used in combination with insulin or sulfonylureas, and dose adjustments of these medications may be necessary.
Severe vomiting or diarrhoea can lead to dehydration and potential kidney problems. Additionally, rapid weight loss and GLP-1/GIP therapy have been associated with gallbladder disease, including gallstones.
Understanding the expected side effect profile is essential for patients and healthcare professionals to distinguish between common, self-limiting reactions and those requiring medical attention. While gastrointestinal symptoms dominate the adverse event profile, patients occasionally report other sensations that warrant exploration, including changes in how they perceive temperature.
Feeling cold or experiencing cold sensations is not listed as an official side effect in the Mounjaro Summary of Product Characteristics (SmPC) approved by the Medicines and Healthcare products Regulatory Agency (MHRA) or in the prescribing information from the European Medicines Agency (EMA). However, anecdotal reports from patients taking tirzepatide and similar GLP-1 receptor agonists suggest that some individuals do experience increased sensitivity to cold or a general feeling of being colder than usual during treatment.
There is no established direct pharmacological mechanism by which Mounjaro would cause cold intolerance. The medication is not known to directly affect thyroid function, peripheral circulation, or thermoregulatory centres in the hypothalamus in ways that would predictably cause cold sensations. Nevertheless, the absence of a direct causal link does not mean patients' experiences are invalid—rather, the sensation of feeling cold may be an indirect consequence of other physiological changes induced by the medication.
It is important to note that clinical trial data for Mounjaro did not identify cold intolerance as a statistically significant adverse event compared to placebo. The SURPASS clinical trial programme, which evaluated tirzepatide in thousands of participants with type 2 diabetes, documented comprehensive safety data but did not highlight temperature perception changes as a notable concern. Post-marketing surveillance continues to monitor for emerging safety signals.
Both patients and healthcare professionals can report suspected side effects via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).
Patients who experience persistent or troublesome cold sensations should discuss these symptoms with their GP or diabetes specialist nurse, as they may warrant investigation for alternative causes unrelated to Mounjaro, such as anaemia, thyroid dysfunction, or other metabolic changes. If you experience cold sensations with sweating, shakiness or dizziness, especially if you also use insulin or sulfonylureas, check your blood glucose as these may be symptoms of hypoglycaemia.
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Although feeling cold is not a documented side effect of Mounjaro specifically, there are several indirect mechanisms through which weight loss medications—and the weight loss they produce—may influence temperature perception and thermoregulation. Understanding these plausible mechanisms helps contextualise patient experiences and guides appropriate clinical assessment.
Rapid weight loss is perhaps the most significant factor. When individuals lose substantial amounts of body weight quickly, they lose both adipose tissue and, to some extent, lean muscle mass. Adipose tissue serves as insulation, helping maintain core body temperature and reducing heat loss to the environment. As this insulating layer diminishes, individuals may genuinely feel colder in ambient temperatures that previously felt comfortable. Additionally, muscle tissue generates heat through metabolic activity; reduced muscle mass can therefore decrease basal heat production.
Metabolic adaptation during weight loss may also play a role. The body often responds to caloric restriction and weight loss by reducing basal metabolic rate—a phenomenon sometimes called "adaptive thermogenesis". This metabolic slowing conserves energy but also reduces heat generation, potentially contributing to cold sensitivity. Research has demonstrated that significant weight loss can decrease resting energy expenditure beyond what would be predicted by changes in body composition alone.
Reduced caloric intake, which often accompanies Mounjaro treatment due to its appetite-suppressing effects, may independently affect thermogenesis. The thermic effect of food—the energy expended in digesting, absorbing, and processing nutrients—contributes to overall heat production. When food intake decreases substantially, this source of heat generation diminishes accordingly.
Finally, changes in circulation may occur during weight loss. Some individuals may experience alterations in peripheral blood flow, which can affect how warm or cold the extremities feel. While evidence specifically linking GLP-1/GIP agonists to altered thermoregulation is limited, the physiological adjustments accompanying significant weight loss may influence subjective temperature perception.
Whilst feeling cold during Mounjaro treatment is generally not a cause for immediate alarm, certain circumstances warrant prompt medical evaluation. Patients should contact their GP or diabetes care team if cold sensations are accompanied by other concerning symptoms that might indicate a more serious underlying condition.
Seek medical advice if you experience:
Severe or persistent fatigue alongside cold intolerance, which could suggest thyroid dysfunction (hypothyroidism), anaemia, or other metabolic disorders
Unexplained weight loss exceeding expected treatment effects, or weight loss accompanied by other systemic symptoms
Changes in heart rate, particularly dizziness or palpitations
Skin changes such as unusual pallor, yellowing (jaundice), or a persistent rash
Shortness of breath or reduced exercise tolerance, which might indicate anaemia or cardiovascular concerns
Swelling of the neck, difficulty swallowing, or voice changes that could suggest thyroid issues
Numbness or tingling in the extremities, which may indicate peripheral neuropathy or circulatory issues
Right upper abdominal pain, fever, or jaundice, which could indicate gallbladder problems
Severe vomiting or diarrhoea leading to signs of dehydration (reduced urination, extreme thirst, dizziness)
Immediate medical attention (call 999 or attend A&E) is required if you develop signs of serious allergic reaction (anaphylaxis), including difficulty breathing, swelling of the face or throat, or severe rash; or symptoms of pancreatitis such as severe, persistent abdominal pain radiating to the back.
If you notice a lump or swelling in your neck, see your GP urgently as this requires assessment under the suspected cancer pathway.
For routine concerns about feeling cold without alarming accompanying symptoms, schedule an appointment with your GP or practice nurse. They can perform a thorough assessment, including relevant blood tests such as full blood count, thyroid function tests, and kidney and liver function tests to exclude other causes. It is helpful to keep a symptom diary noting when cold sensations occur, their severity, and any associated factors such as timing relative to Mounjaro injections or meals.
For urgent but non-life-threatening concerns outside of GP hours, contact NHS 111 for advice.
If you experience increased sensitivity to cold whilst taking Mounjaro, several practical strategies can help you maintain comfort whilst continuing your treatment. These approaches address the symptom without necessarily requiring medication changes, though any persistent concerns should be discussed with your healthcare team.
Practical measures to stay warm:
Layer clothing appropriately: Wear multiple thin layers rather than single thick garments, as this traps insulating air and allows you to adjust to varying temperatures throughout the day
Focus on extremities: Keep hands, feet, and head covered, as these areas lose heat disproportionately. Thermal socks, gloves, and hats can make a significant difference
Maintain adequate nutrition: Whilst Mounjaro reduces appetite, ensure you consume sufficient calories and nutrients to support metabolic function. Work with a dietitian if needed to develop an appropriate eating plan
Stay physically active: Regular exercise generates body heat and helps maintain muscle mass, which is important for thermogenesis. Aim for a combination of cardiovascular and resistance training as advised by your healthcare team
Monitor hydration: Adequate fluid intake supports circulation and overall metabolic function
Adjust your environment: Keep indoor temperatures comfortable and use blankets or heating devices as needed
Nutritional considerations are particularly important. Ensure adequate protein intake to help preserve lean muscle mass during weight loss. Include iron-rich foods (lean meat, pulses, fortified cereals, dark green vegetables) to prevent anaemia, and consider foods rich in B vitamins and iodine from dietary sources (such as dairy products, fish and seafood) to support metabolic function.
If you are taking insulin or sulfonylureas alongside Mounjaro, remember to recognise and treat hypoglycaemia promptly. Check your blood glucose if you experience symptoms such as feeling cold with sweating, shakiness, hunger or dizziness, and follow your healthcare team's advice for treating low blood glucose.
Do not discontinue Mounjaro without consulting your prescriber, even if you find cold sensations bothersome. The medication provides important benefits for diabetes management and weight loss. Your healthcare team can assess whether the symptom represents a genuine concern, explore alternative explanations, and help you weigh the benefits of continuing treatment against any discomfort. They may also consider adjusting your dose titration schedule if symptoms are troublesome. In most cases, temperature sensitivity improves as weight loss stabilises and the body adapts to its new composition.
No, Mounjaro does not directly cause cold intolerance through its pharmacological action. However, the substantial weight loss it produces may indirectly lead to increased cold sensitivity due to loss of insulating body fat and metabolic adaptation.
Contact your GP if cold sensations are accompanied by severe fatigue, unexplained weight loss beyond expected effects, heart rate changes, skin changes, shortness of breath, or swelling of the neck, as these may indicate thyroid dysfunction, anaemia, or other conditions requiring investigation.
Wear layered clothing, keep extremities covered, maintain adequate nutrition with sufficient protein and calories, stay physically active to preserve muscle mass, and ensure proper hydration. Do not stop Mounjaro without consulting your prescriber.
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DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
