If you've found yourself reaching for extra jumpers, cranking up the heating, or wondering why your hands and feet are always freezing since starting Mounjaro, you're experiencing a surprisingly common side effect. Feeling colder than usual isn't officially listed among the main side effects, but many people notice it during their weight loss journey. This article explains why it happens and what lifestyle changes can help you manage it.

Feeling cold on Mounjaro is typically caused by eating less and losing body fat, both of which reduce your body's heat production and insulation. It's usually harmless, though occasionally it can signal nutritional issues worth addressing.

Key takeaways

Reduced calorie intake means your body produces less heat as a byproduct of digestion

Losing body fat removes natural insulation, making you more sensitive to cold

Feeling cold is usually harmless but can sometimes indicate you're not eating enough

If cold sensitivity is severe or accompanied by fatigue, hair loss, or dizziness, speak to your GP

Why does Mounjaro make you feel cold?

Several factors contribute to feeling colder on Mounjaro, most of which relate to how the medication affects your eating and metabolism.

Mounjaro contains tirzepatide, which belongs to a class of medications called GLP-1 receptor agonists. It works by mimicking hormones that regulate appetite and blood sugar, affecting how your body processes insulin and glucose. The result is reduced appetite and significant weight reduction, but these same changes can leave you feeling colder than before.

A person in cosy winter clothing holding a warm mug, surrounded by symbols representing body heat, a thermometer, and warmth indicators.

You're eating fewer calories

Food is fuel, and your body generates heat when it digests food. This process, known as diet-induced thermogenesis, means that eating triggers heat production as a natural byproduct. When you eat less (as most people do on Mounjaro), your body simply produces less heat.

Think of it like a fire that's been given less wood. It still burns, but not as hot. Your body is running on less fuel, which means less warmth.

You're losing insulating body fat

Fat tissue acts as insulation, helping your body retain heat. As you lose weight on Mounjaro, you lose some of this natural insulation. Areas that were previously well-padded may now feel the cold more.

This is particularly noticeable in extremities like hands and feet, and in areas where you've lost significant fat. In clinical trials, people taking tirzepatide (Mounjaro's active ingredient) lost an average of 15–22.5% of their body weight over 72 weeks (Jastreboff et al., 2022), which represents a substantial reduction in insulating tissue.

Your metabolism may be adjusting

When you lose weight, your body often adjusts by becoming more energy-efficient. This metabolic adaptation (your body becoming more efficient with energy) means it may burn slightly fewer calories at rest than it did before, producing less heat in the process.

This is a normal response to weight loss, not specific to Mounjaro. However, because Mounjaro can cause relatively rapid weight loss, the effect may be more noticeable.

Blood flow changes

Some people notice that their circulation seems different on Mounjaro, with hands and feet feeling particularly cold. This could relate to changes in blood pressure, blood sugar regulation, or simply having less insulating tissue around blood vessels.

If cold extremities are accompanied by colour changes (fingers turning white or blue), this might indicate a circulation issue worth discussing with your doctor.

Reduced muscle mass

If you're losing weight quickly and not doing resistance exercise, you may lose some muscle along with fat. Muscle tissue is metabolically active, meaning it burns calories and generates heat even at rest. Less muscle means less heat production.

This is one reason why maintaining adequate protein intake and doing some form of strength training is recommended during weight loss.

An infographic showing five causes of feeling cold on Mounjaro: eating fewer calories, losing insulating fat, metabolism adjusting, blood flow changes, and reduced muscle mass, each with a simple icon.

Is feeling cold on Mounjaro normal?

Yes, for most people feeling colder is a normal consequence of eating less and losing weight. It's not a sign that something is wrong with the medication or your body.

However, the severity varies. Some people notice a slight increase in sensitivity to cold, whilst others feel perpetually freezing. Your experience depends on:

How much weight you've lost
How quickly you've lost it
How much you're eating
Your baseline metabolism and body composition
Environmental factors (it's more noticeable in winter)

When feeling cold might signal a problem

Whilst feeling colder is usually harmless, sometimes it can indicate issues worth addressing.

Inadequate calorie intake

If you're feeling extremely cold, weak, and tired, you might not be eating enough. Mounjaro suppresses appetite significantly, and some people end up eating far too little.

Your body needs a minimum amount of fuel to function properly. Severely restricting calories can cause your metabolism to slow dramatically, leaving you feeling cold, exhausted, and unwell.

If you're eating less than 1,200 calories daily for an extended period, try to eat more, even if you're not hungry. The NHS recommends that very low-calorie diets should only be followed under medical supervision.

Thyroid issues

Feeling cold is a classic symptom of an underactive thyroid (hypothyroidism). Whilst Mounjaro doesn't cause thyroid problems, rapid weight loss can occasionally unmask underlying thyroid issues.

If feeling cold is accompanied by other symptoms like significant fatigue, hair loss, dry skin, constipation, or unexplained weight gain (despite Mounjaro), ask your GP about thyroid testing. The NHS has information about thyroid function tests.

Iron deficiency or anaemia

Feeling cold, especially in your hands and feet, can be a sign of iron deficiency or anaemia. If you're eating less overall, you may not be getting enough iron from your diet.

Other signs of anaemia include fatigue, pale skin, shortness of breath, vertigo and balance issues. A simple blood test can check your iron levels. See the NHS guide to iron deficiency anaemia for more information.

Poor circulation

If your extremities are very cold, changing colour (white, blue, or red), or numb, this could indicate a circulation problem rather than a normal Mounjaro side effect. Mention this to your doctor, particularly if you have other cardiovascular risk factors.

Low blood sugar (hypoglycemia)

If you're taking Mounjaro alongside diabetes medications, feeling cold can sometimes be a sign of low blood sugar (hypoglycemia). Other symptoms include shakiness, sweating, confusion, and irritability. If you experience these symptoms, check your blood sugar levels and speak to your prescriber about adjusting your diabetes medications.

How to manage feeling cold on Mounjaro

You can't entirely prevent feeling colder if you're eating less and losing fat, but several strategies can help you stay comfortable.

Dress in layers

The obvious solution is often the best. Dress in layers so you can adjust throughout the day as your body temperature fluctuates. Keep extra jumpers at work, in the car, and around the house.

Thermal underlayers can make a significant difference without adding bulk.

Keep your extremities warm

Hands, feet, and ears often feel the cold most. Invest in warm socks or thermal insoles, gloves for outdoor wear, a good hat to keep your head warm, and hand warmers for particularly cold days.

Eat regular meals

Even if you're not hungry, eating regular meals helps maintain your body's heat production. Don't skip meals entirely, as this can worsen the cold feeling.

Include plenty of fibre-rich foods like vegetables, wholegrains, and legumes alongside your meals. While fibre doesn't directly warm you up, it helps maintain steady energy levels and prevents blood sugar dips that can leave you feeling cold and tired.

Warm foods and drinks can provide an immediate warming effect. Soups, stews, porridge, and hot drinks feel more satisfying when you're cold.

Stay active

Physical activity generates heat and improves circulation. Even a short walk or some light stretching can warm you up when you're feeling chilly.

Regular exercise also helps maintain muscle mass, which contributes to heat production.

Eat enough protein

Protein has a higher thermic effect than carbohydrates or fat, meaning your body generates more heat digesting it. Research shows protein increases metabolic heat production by 20–30%, compared to 5–10% for carbohydrates and 0–3% for fat (Westerterp, 2004).

Ensuring adequate protein intake (1.0–1.2g per kilogram of body weight during weight loss, roughly 80–100g daily for someone weighing 80kg) can help with heat production.

Good protein sources include lean meats and poultry, fish, eggs, Greek yoghurt, legumes and pulses, and tofu or tempeh.

Don't restrict calories too severely

If you're perpetually freezing, weak, and tired, you may be eating too little. Mounjaro works even without extreme calorie restriction. Try to eat at least 1,200–1,500 calories daily (more if you're active or have a larger body).

Your body needs adequate fuel to function, including regulating temperature.

Stay hydrated

Proper hydration supports your body's ability to regulate temperature. The NHS Eatwell Guide recommends 6–8 glasses of fluid daily as a baseline. During weight loss, aim for at least 2 litres of water daily to support your body's temperature regulation and overall wellbeing.

Keep your home warm

Adjust your heating to compensate for your reduced tolerance to cold. It might cost a bit more, but being comfortable at home matters for your wellbeing.

Use hot water bottles, electric blankets, or heated throws to warm up without heating the entire house.

Have warm drinks throughout the day

Hot tea, coffee, or simply warm water with lemon can help you feel warmer from the inside. Avoid excessive caffeine, which can affect circulation, but moderate amounts are fine.

Limit alcohol, as it can initially make you feel warm but actually causes your body to lose heat more quickly. Alcohol also affects blood sugar levels, which can contribute to feeling cold. Stick to warming non-alcoholic options like herbal teas, broths, or warm water with lemon.

Herbal teas like ginger or cinnamon can feel particularly warming. :::

Feeling cold alongside other side effects

Feeling cold often occurs alongside other Mounjaro side effects that relate to reduced calorie intake. You might also experience:

Fatigue from reduced calorie intake: also caused by eating less
Hair thinning: related to rapid weight loss
Headaches: can be triggered by inadequate intake
Dizziness: may indicate dehydration or low intake

If you're experiencing several of these symptoms together, review whether you're eating and drinking enough. These symptoms often improve with better nutrition.

When to see a doctor

Contact your GP or prescriber if

Cold sensitivity is severe and affecting your quality of life
You have other symptoms suggesting thyroid problems (fatigue, hair loss, unexplained weight changes, constipation)
Your extremities change colour (white, blue) or become numb
You feel unwell alongside feeling cold
Cold sensitivity is accompanied by significant weakness or dizziness
Symptoms persist despite eating adequate calories and protein

Seek immediate medical help if you experience

Severe abdominal pain alongside feeling cold, as this could indicate gallbladder problems, which are more common during rapid weight loss. While rare, gallbladder issues require prompt medical attention.

Your doctor can check for underlying issues like thyroid dysfunction or anaemia with simple blood tests.

Does feeling cold improve over time?

For many people, yes. As your body adjusts to its new weight and eating patterns, the intense cold sensitivity often moderates. However, if you've lost significant weight, you may find you're generally more sensitive to cold than you were before, simply because you have less insulation.

This is a trade-off many people are happy to accept for the benefits of weight loss. Wearing warmer clothes is a small price for improved health.

The bottom line

Feeling cold on Mounjaro is common during the weight loss journey, caused primarily by eating less (which reduces heat production) and losing body fat (which reduces insulation). For most people, it's a harmless part of the weight management process, though it can be annoying.

Dressing warmly, eating regular meals with adequate protein, staying active, and keeping your home heated can help manage the discomfort. Simple lifestyle adjustments make a real difference. If cold sensitivity is extreme or accompanied by other symptoms like significant fatigue or hair loss, speak to your GP to rule out underlying issues like thyroid problems or anaemia.