CPR First Aid

Can Blood Freeze

Can Blood Freeze?

When up against the extreme cold, our bodies go through various processes to survive. However, if the cold becomes too unbearable, then people’s health takes a huge hit. A wave of negative symptoms comes into play, either causing discomfort, pain and if not taken care of, death. 

One of the most common and dangerous freezing symptoms is frostbite. If left out in the extreme cold, this can result in permanent injury to skin, fingers, toes, and ears just to name a few. 

One interesting aspect to examine though is whether blood is affected by freezing temperatures. 

Cosy up and keep warm as we answer the question, can blood freeze? 

How Do Our Bodies Act in Extreme Temperatures?

It may prove worthwhile to understand how our bodies react when exposed to extreme temperatures, whether for short or long periods of time. 

The body does its absolute best to maintain equilibrium in terms of body temperature. The brain and the blood vessels work in tandem to respond to various weather conditions. 

Defence Against Cold

When it is cold, defence mechanisms are triggered to help us retain our core temperature or the temperature that our internal organs need to keep working. 

When our body feels the cold, it sends a message to our body’s thermostat. This thermostat is the hypothalamus found in the brain. Once the message is received, the brain will do everything it can to keep us warm and operational on the inside. In most cases, it may even sacrifice several extremities like our fingers and toes. 

In addition, it also narrows the blood supply to various parts of the body, namely the skin. Again, this is all done to preserve the inner temperature our organs need to survive. 

Defence Against Heat

Our body’s defences are not partial to cold. Extreme heat can also push our bodies out of their equilibrium. 

As one would expect, the body does the opposite of what it does in the cold. Instead of narrowing or constricting the blood vessels, it instead dilates them so that the body can release heat and live in equilibrium.

If the heat becomes too unbearable though, people may succumb to things like heat stroke.  

The push and pull of blood circulation are at the core of how our bodies regulate temperature. 

What is the Ideal Core Temperature?

Up until now, we have spoken about our body’s core temperature and keeping equilibrium. However, what is this ideal core temperature? 

The normal range of a body’s temperature goes from 36.1°C up to 37.2°C. If a person’s body temperature goes over or under this ideal range for a prolonged period of time, it will introduce a variety of complications and symptoms to a person. 

Can Blood Freeze?

After learning about our bodies, we now get to the crux of our learning. Is it possible to have frozen blood? The answer may not be as simple as one would suspect. In fact, the answer shifts in terms of perspective and context. 

Out of Body

If all we want is to know whether blood can freeze, then it becomes a simple question, with the accompanying simple answer of yes. This answer though is only for when the blood is out of our bodies.

Frozen blood occurs at a temperature of -2 to -3°C. However, this freezing point is for blood outside of our bodies. Many procedures use this, with the most common one being blood donations. Scientists may freeze and keep the donated blood until needed. 

What about the blood within our bodies? 

Within Our Body

Despite the freezing temperature of the blood being around -2 to -3 or even -8°C, this doesn’t affect the blood in people’s bodies when they are alive. This is why we humans are called “warm-blooded” beings. 

This title is not just for show. People’s bodies constantly create and dispel heat so that extreme weather conditions do not spell death for us. 

Heat is created through metabolism, helped by the calories – or the amount of heat or energy it has – from the food we eat. This, along with how our bodies react to extreme hot and cold temperatures allows us to survive.

The only time people can have frozen blood when inside the body is when they are no longer living. 

Caution With Cold

Some people may find it reassuring that blood can’t really freeze in our bodies. However, that doesn’t mean that people should carelessly waltz into extremely cold temperatures. It can bring about cold-related illnesses and conditions. Let’s take a look at some of them. 


This condition usually affects the extremities like our toes, fingers, nose, and ears. It happens when the small blood vessels under the skin get inflamed due to exposure to cold temperatures, either through direct contact or because of damp conditions. 

The symptoms include itchiness, redness, swelling, and sometimes blistering. In severe cases, it can lead to permanent nerve damage. 


Frostbite is the more serious condition that may develop from prolonged exposure to cold temperatures. It happens when the water in our cells freezes solid. 

The most common places for this to happen are on our extremities like our toes, fingers, and nose. However, it can also happen on other exposed skin like our cheeks and chin. 

The symptoms at first are similar to chilblains. It starts with a prickling or stinging sensation followed by numbness. The skin then turns red or pale. In more severe cases, the skin turns black and hard as the tissue dies. 

This is why it’s important to get out of the cold and warm up as soon as possible if you notice these symptoms. 


Hypothermia is a condition that usually happens when a person is exposed to cold weather for a prolonged period of time, whether through rain, snow, or wind. It can also happen if a person gets wet and cold, whether from sweat, clothes, or water. Babies and elderly people are also more susceptible to this condition. 

The symptoms include shivering, confusion, sleepiness, and slow reactions. In extreme cases, a person may become unconscious. 

Things to Remember to Battle the Cold

Despite the dangers that come with cold weather, there are many things people can do to protect themselves. Let’s take a look at some of them. 

Wear Appropriate Clothes

This is a no-brainer. When going out in cold weather, it’s important to wear clothes that will keep you warm. This means layering up with clothes made from materials like wool and cotton. You should also avoid wearing wet clothes as they will make you colder. 

Stay Dry

As mentioned before, getting wet in cold weather can lead to hypothermia. This is why it’s important to stay dry when you’re out in the cold. If you do get wet, change into dry clothes as soon as possible. 

Limit Your Time Outside

It’s important to limit your time outside in cold weather. If you can, stay indoors where it’s warm. If you have to go out, make sure to dress appropriately and come back inside as soon as possible. 

Eat Warm Foods and Drink Hot Beverages

Eating warm foods and drinking hot beverages can help keep you warm from the inside out. This is because they raise your body temperature. Soups and stews are great examples of warm food, while tea and coffee are great hot beverages. Just make sure not to drink alcohol as it can actually make you feel colder. 


So, can blood freeze? It can when it is outside of the body.

Even though the chances of frozen blood within our bodies are slim to none, that doesn’t mean we should take the cold weather lightly. There are many conditions and illnesses that come with exposure to cold temperatures.

If you or your loved one get afflicted with any cold-related illness or condition, we hope the information we have shared with you will come in handy.

It is always best to supplement this type of knowledge with practical first aid skills. They will allow you to respond to someone in need and hopefully save a life.

Learn more by taking CPR First Aid’s Liverpool course today.

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