Can Mounjaro Make You Feel Cold? Causes & Tips on Tirzepatide UK

Can Mounjaro make you feel cold?

Some people taking Mounjaro (tirzepatide) notice they feel colder than usual especially in the first few months, when appetite drops and weight loss can be fastest.

Here’s the key point: feeling cold isn’t listed as an official side effect in the UK Summary of Product Characteristics (SmPC) for Mounjaro, which is the regulator-approved prescribing information. (medicines.org.uk)

So what’s going on? In most cases, it’s not a direct drug effect. It’s more often a knock-on effect of the changes Mounjaro can trigger like eating less, losing body fat, moving less while you adjust, or (occasionally) uncovering an underlying issue such as anaemia or thyroid problems.

This guide explains the most likely reasons you feel chilly on Mounjaro, what you can do today, and when it’s worth getting checked.

Why you might feel colder on Mounjaro (even if it’s not a listed side effect)

1) You’ve lost some of your ‘insulation’

Body fat — especially subcutaneous fat under the skin — acts as insulation. When you lose it, you can feel cold sooner, particularly in hands, feet, and when sitting still.

Research on thermoregulation shows that leaner people tend to have a higher “lower critical temperature” — meaning the environment has to be less cold before the body starts working harder to generate heat. In plain English: as you get smaller, you may start feeling chilly at temperatures you used to find comfortable. (pubmed.ncbi.nlm.nih.gov)

2) You’re eating less, so you’re producing less heat

Food doesn’t just provide energy, digestion itself produces heat (diet-induced thermogenesis). When Mounjaro reduces appetite, it’s easy to unintentionally under-eat, especially at the start.

On top of that, weight loss can cause metabolic adaptation (sometimes called adaptive thermogenesis): your body becomes more efficient and total energy expenditure can drop, which can translate into feeling colder.

3) You may be moving less (and muscle is your internal ‘radiator’)

When you’re in a calorie deficit, you may naturally fidget less and feel more tired. Less movement = less heat.

Muscle tissue also helps generate heat. If weight loss is rapid and protein intake or resistance training is low, you can lose some lean mass and feel colder.

The UK Chief Medical Officers recommend adults aim for strengthening activities on at least 2 days per week, alongside weekly aerobic activity. (gov.uk)

4) Nutrient gaps (iron, B12/folate) can creep in

Appetite suppression can make it harder to get enough iron, vitamin B12, and folate — all important for healthy red blood cells and oxygen delivery.

Iron deficiency anaemia commonly causes fatigue and shortness of breath. (nhs.uk)
Vitamin B12/folate deficiency can also cause tiredness and neurological symptoms like pins and needles. (nhs.uk)

5) Underactive thyroid (hypothyroidism)

An underactive thyroid is a common cause of feeling cold more than usual and it’s easy to mistake for a medication issue.

NHS-listed symptoms include fatigue, weight gain, constipation, low mood, dry skin/hair, and feeling cold more than usual. (nhs.uk

If cold intolerance is new, persistent, or worsening, it’s worth discussing thyroid blood tests with your GP.

6) Dehydration after GI side effects

Nausea, vomiting, and diarrhoea are common early side effects of tirzepatide. The SmPC warns GI effects may lead to dehydration and, in some cases, worsening kidney function. (medicines.org.uk)

Dehydration and lower blood volume can leave you feeling washed out and cold, particularly in extremities.

Cold sensitivity vs chills: a quick check

Feeling colder than normal isn’t the same as ‘shivers’ from illness. Use this simple guide:

When to speak to your prescriber or GP

Book a review if cold intolerance is:

• New and persistent (most days for 2–3+ weeks)
• Getting worse rather than stabilising
• Affecting sleep or day-to-day function
• Happening alongside fatigue, dizziness, breathlessness, palpitations, hair loss, constipation, low mood, or heavy periods

If you have diabetes and symptoms suggest a hypo, follow NHS guidance and seek help if you have severe or repeated episodes. (nhs.uk)

When to seek urgent medical help

Call 999 / go to A&E if you think you (or someone you’re caring for) may have hypothermia.

NHS-listed symptoms include shivering, pale/cold/dry skin, slurred speech, slow breathing, tiredness, and confusion. (nhs.uk)

Can you report this as a side effect?

Yes. Even if you’re not sure Mounjaro caused it, you can report suspected side effects via the MHRA Yellow Card scheme (website or app). This helps regulators spot patterns that may not have shown up clearly in trials. (gov.uk)

Frequently asked questions

Will feeling cold on Mounjaro go away?

Often it improves once your intake stabilises, weight loss rate slows, and you build consistent movement/strength training. If it doesn’t, get checked for thyroid issues, anaemia, or B12/folate deficiency.

Is it dangerous?

Usually it’s more annoying than dangerous. But cold intolerance can be a clue to something treatable (like hypothyroidism) and shouldn’t be ignored if it’s persistent or severe. (nhs.uk)

Should I take iron or B12 supplements ‘just in case’?

It’s better to speak to a clinician first. Supplements can be helpful when you’re deficient, but the right choice depends on the cause and your blood results.

Could it be low blood sugar?

If you have diabetes (especially if you use insulin or a sulphonylurea), it could be. Check your glucose if you can and treat as a hypo if low. (nhs.uk)

Medical note: This article is for general education and does not replace personalised medical advice. If you’re worried about symptoms or side effects while taking tirzepatide, contact your prescriber or GP.