We asked a doctor what it could mean if you’re frequently freezing.

Some people always seem to be cold.

What on earth is going on?

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Eva Blanco/Getty Images

(Note that she says in theabsenceof any medical reason.

That means this persistent feeling of cold isn’t tied to an underlying health condition.)

So why does this happen?

It could be due to lower muscle mass, according to Dr. Agarwal.

“Some people have lower muscle mass relative to body surface area,” she says.

This can cause your hands and feetand maybe your entire bodyto feel cold.

The how and why of it is a little complicated.

Your body’s sleep cycle is regulated by your circadian rhythmsometimes called your body’s internal clock.

Both internal and external cues like light, temperature, and hormones help tell your body what to do.

When your circadian rhythm thinks it’s time to go to sleep, your body does a few things.

Your brain releases melatonin, a hormone that promotes sleep, and your internal temperature will drop.

“The circadian rhythm causes our body temperature to drop during sleep,” Dr. Agarwal says.

Poor Circulation

Your circulatory system is responsible for circulating blood throughout your body.

According to Dr. Agarwal, there are many different reasons why you might have poor circulation.

There are two reasons behind this.

Vitamin B12 Deficiency

Vitamin B12plays a role in several of your body’s key functions.

However, some are at higher risk of experiencing vitamin B12 deficiency than others.

Vitamin B12 Deficiency symptoms:

Hypothyroidism

If you have hypothyroidism, you have an underactive thyroid.

Your thyroid is a small gland that produces hormones that affect the way your body uses energy.

An underactive thyroid means your thyroid gland isn’t producing enough hormones to meet your body’s needs.

And one of the symptoms associated with hyperthyroidism is cold intolerance.

Blood Vessel Disorders

A couple of different blood vessel disorders have been linked to cold intolerance.

These include: Peripheral Arterial Disease and Raynaud’s disease.

Diabetes

Diabetes is a health condition characterized by too-high glucose levels.

It happens when your blood sugar (blood glucose) is too high.

There are two kinds of diabetes: pop in 1 diabetes and pop in 2 diabetes.

If you have pop in 2 diabetes, your body doesn’t produce or use insulin well.

You might just be someone who runs cold or someone who needs to get more sleep.

Young, Michael N. Sawka and Kent B.Physiology of Cold Exposure.

Nutritional Needs In Cold And In High-Altitude Environments: Applications for Military Personnel in Field Operations.

National Institute of General Medical Sciences.Circadian rhythms.

National Heart and Blood Institute.How smoking affects the heart and blood vessels.

Patterson RE, Laughlin GA, Sears DD, et al.Intermittent fasting and human metabolic health.J Acad Nutr Diet.

American Thyroid Association.Hypothyroidism (Underactive).

National Heart, Lung and Blood Institute.What is anemia?