BLOOD TESTS ∙ 3 minutes read

6 interesting facts about blood you might not know

By Ashton Sheriff | Medically reviewed by Dr Luke Pratsides

Did you know your blood is full of hidden wonders? It’s a cocktail of molecules and cells that help to keep your body functioning properly and, most importantly, keep you alive. 

There’s a lot to learn about the blood - and a lot your blood can teach you - so we’ve devised a list of 6 of the most interesting facts about blood to inspire you to appreciate it in all its crimson glory. 

1. Human blood contains gold 

Yes, you read that correctly. It’s almost impossible to believe, but human blood actually contains traces of gold. In total, the human body contains less than 0.2 mg gold - and most of it can be found in the blood. 

Our bodies also contain a wonderfully peculiar mix of other elements, such as silicon (which is used to make computer chips), vanadium (used in the construction of nuclear reactors), and tin (used in the production of food cans). 

2. Your blood can tell you more about your health than your eyes can

Our eyes are an important tool for assessing our health. A quick scan of the body or even a glance in the mirror is enough for us to make judgements about the state of our health. If we look good, we often assume we’re healthy. If we notice something unusual, we assume the contrary.

But as good as our eyes are for assessing our health, our blood can reveal far more. That’s because it shows many health indicators our eyes can’t detect, such as cholesterol levels. High cholesterol is particularly dangerous because it often doesn’t have any symptoms. If cholesterol levels are too high it can build up in the arteries and cause blockages, increasing the risk of heart attacks and strokes. 

Cholesterol levels - and other key health factors - can only be measured with a blood test. There are many different types of blood tests that can be used to measure specific aspects of your health, and nowadays blood tests can be taken safely from the comfort of home. 

For example, you could use a Vitamin D Test Kit to measure your vitamin D levels. Or, if you’d rather cover all the bases with a general health check-up, you could take an At-Home Health MOT to measure a wider range of health indicators - including cholesterol levels and liver function. 

The blood can give valuable (and even life-saving) information about organ health, general health, and even long-term health. So, it’s important that we listen to our blood to better understand our bodies and take the steps needed to keep them healthy. 

3. The human body makes about 2 million red blood cells a second 

The body is one of the most efficient factories on earth. It constantly produces billions of new cells to replace old and worn-out ones - and it does it without you even noticing. 

In fact, it’s estimated that the human body replaces a whopping 330 billion cells a day. This number is even more astounding when you realise that it only accounts for about 1% of all our cells. 

Red blood cells in particular are produced at a mind-blowing rate. Believe it or not, the body makes 2 million of them a second. Our bodies need so many red blood cells because they continuously supply oxygen to our cells. Without enough red blood cells our bodies wouldn’t be able to function properly, so they need to be generated constantly to keep us healthy and active. 

4. Blood is not always red

The first thing most people think of when they hear the word “blood” is the brilliant, vivid red liquid that courses through our veins. But did you know that blood comes in different colours, including green and blue?

We humans have red blood because our red blood cells are packed with haemoglobin - an oxygen-carrying protein that contains iron. It’s the presence of iron that turns our blood red when it’s exposed to air (i.e. whenever you see it outside your body). 

However, certain species of octopus have blue blood because the protein that carries oxygen in their body is hemocyanin, which is rich in copper. Snails, spiders, slugs, and squid also have blue blood for the same reason. 

If you thought that was wild, the green-blooded skink of Papua New Guinea has, you guessed it, green blood. And the ocellated icefish found in Antarctica has blood that is completely clear. 

Blood comes in a spectrum of colours in the natural world. Whether it’s red, green, yellow, or blue, blood can tell us a lot about the creatures around us - as well as ourselves. So, pay close attention to your blood. The wonders it holds contain many answers that help us to better understand how we work. 

5. Blood group O is the most common blood group in the UK

Like the four houses in Harry Potter, there are four different blood groups: A, B, O, and AB. The difference between them lies in the presence (or absence) of certain antibodies and antigens. 

Antibodies and antigens are molecules in the body that help to protect us from infection (e.g. from dangerous viruses and microorganisms). Each blood group contains a different assortment of antibodies and/or antigens: 

Blood groups that contain antibodies and antigens

  • Blood groups A and B

Blood groups that contain antibodies only (no antigens)

  • Blood group O

Blood groups that contain antigens only (no antibodies) 

  • Blood group AB

Blood group O is the most common blood group in the UK. Almost half of the UK population (48%) has blood group O. 

But why do blood groups matter? 

It’s vital to be aware of a person’s blood group because they must be given blood that matches their blood group if they ever need to have a blood transfusion. 

A person may need a blood transfusion if they’ve had a serious accident or if they are undergoing surgery. A blood transfusion helps to replenish lost blood so that they can stay alive even after a significant injury or surgery. 

However, if they are given the wrong blood group then this can cause severe health complications, as their own blood will recognise the new foreign blood cells and attack them. Therefore, knowing a person’s blood group before they receive any blood is crucial for ensuring their safety. 

6. Mosquitoes prefer people with blood group O

Have you ever been abroad only to have the mosquitoes practically eat you alive as soon as you arrive? 

If you answered “yes”, then perhaps you have blood group O.  

A study found that mosquitos are more attracted to those with blood group O. A group of brave volunteers stuck their arms into a repurposed fish tank filled with bloodthirsty mosquitoes* to see which blood group they’d be most attracted to. The results showed that more mosquitoes landed on the forearms of those with blood group O than any other blood group - particularly those who were blood group O “secretors”. 

It turns out that we, as humans, can secrete substances from our skin that give away our blood types. Mosquitoes may be able to detect these secretions and hone in on their favourite blood groups. However, it’s worth noting that the scientists themselves thought that these secretions were too subtle to be detected by mosquitos, so it’s still unclear whether this is the true reason why mosquitoes prefer blood group O. 

*The mosquitoes had their suckers (probosces) amputated so they couldn’t bite the volunteers. But still, it takes some bravery to stick your hand into a tank infested with insects!

The bottom line

Blood holds many wonders. Aside from being filled with molecules that help to keep you alive, it also contains crucial information about your health. Your blood can tell you more about your health than your eyes can, which is why it’s recommended you take a home blood test to get a clearer picture of your health inside and out. Once you’ve listened to what your blood has to say about your health, you’ll have a better understanding of your body and be able to take the steps needed to optimise your health accordingly. 

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