Is feeling cold a side effect of Mounjaro?

Does Mounjaro itself cause you to feel cold?

Looking at the Mounjaro SmPC and the NHS medicines page for tirzepatide, feeling cold is not included among the recognised side effects. The listed effects are dominated by the gastrointestinal system: nausea, vomiting, diarrhoea, constipation, and indigestion feature most prominently, especially in the early weeks of treatment or after a dose increase. Fatigue and headache also appear. Cold sensation does not.

That does not mean your experience is not real. It means the mechanism is almost certainly indirect. Tirzepatide works partly by reducing appetite through its action on GIP and GLP-1 receptors, so most people eat considerably less (sometimes dramatically less) soon after starting. A sustained reduction in calorie intake lowers the metabolic rate slightly, which means the body generates a little less heat. That shift can be enough to make you notice the cold more, particularly in your extremities.

Fat tissue also provides thermal insulation. As treatment progresses and body fat reduces, some people find they feel chilly in rooms or at temperatures that never used to bother them. This is the same phenomenon reported by people who lose weight through any means, not something specific to tirzepatide. If you want to explore whether feeling cold is a side effect of Mounjaro in more detail, we cover that question fully in a dedicated page. For a fuller picture of what the medicine's prescribing information does cover, our overview of Mounjaro side effects is a useful starting point.

Could there be another explanation worth ruling out?

Yes, and this is the part that matters clinically. Several conditions that are entirely unrelated to Mounjaro can cause persistent cold feelings, and they are worth mentioning to your GP or prescriber if the sensation is new, worsening, or accompanied by other symptoms.

An underactive thyroid (hypothyroidism) is one of the more common causes of feeling cold all the time, along with fatigue, dry skin, and weight changes. Iron-deficiency anaemia is another. Neither is caused by tirzepatide, but both can develop independently and overlap with treatment. If you started Mounjaro recently and cold feelings appeared around the same time, it is natural to attribute them to the medicine. It may still be a coincidence.

Fatigue is a recognised tirzepatide side effect, and tiredness and cold feelings sometimes travel together. If you are also experiencing unusual tiredness, our page on tiredness as a Mounjaro side effect covers what is known there. The rule of thumb: if the cold feeling is mild and tied to eating less or losing weight, monitor it. If it is severe, sudden, or paired with something else that feels wrong, get it checked.

When should you seek medical help?

Most people who notice cold feelings on Mounjaro do not need urgent care. But certain combinations of symptoms are a reason to contact a healthcare professional the same day or call 111.

Seek prompt medical attention if feeling cold comes with: severe, persistent abdominal pain that spreads to your back (a potential sign of pancreatitis, the MHRA issued a Drug Safety Update on this risk for GLP-1 medicines in January 2026); signs of dehydration such as very dark urine, dizziness, or a rapid heartbeat following vomiting or diarrhoea; or symptoms that suggest an allergic reaction, including swelling of the face, lips, or throat, or difficulty breathing. These are not common, but they are serious.

A broader guide to the possible side effects of Mounjaro sets out the full range from mild and expected to symptoms that need faster attention. The Mounjaro side effects resource covers what to watch for at each stage of treatment. If you are unsure whether what you are experiencing needs attention, contacting your prescriber is always the right move. You can also report any unexpected symptom to the MHRA through the Yellow Card scheme, it takes a few minutes and genuinely contributes to post-market safety monitoring.

What can you do if you are feeling cold during treatment?

Practically, there is quite a lot you can manage at home while this settles. Protein is the macronutrient most associated with thermogenesis, the body burns more energy digesting it than fat or carbohydrate. Keeping protein intake adequate while eating less overall helps support your metabolic rate, which may reduce the cold feeling. Aim to stay warm and layer up, particularly in the evenings; the drop in calorie intake often makes late-day chills more noticeable, and some people find it worse after the weekly injection when nausea dips their appetite further.

Hydration matters too. If nausea has made you drink less, mild dehydration can amplify feelings of cold and fatigue. Small, regular sips throughout the day (the kind of thing you would remind yourself of before the school run) are easier to manage than large amounts at once.

If cold intolerance is affecting your quality of life or you are worried it signals something beyond simple calorie reduction, raise it at your next clinical review. Our prescribers are there for exactly this kind of conversation, not just to issue a prescription but to support you through treatment. You can explore all of our weight-loss treatment options or read more about approaching weight loss with clinical support. If you have not yet started and want to discuss how the medicine might suit you, a free consultation with our prescribing team is the natural first step.