Millions of people are alive today because they received the blood given by another person. June 14 is World Blood Donor Day. This is the day on which we can say thank you to those who give blood. Every country raises awareness of the importance of giving blood. Most blood donors give blood voluntarily, but some countries pay for people to give blood. Doctors say the blood from unpaid donors is generally safer. The blood donation system is pretty much the same all around the world. You give blood and then get a free cup of tea, and perhaps a biscuit. There is a greater need for blood in developing countries. Under 40% of the world’s blood supply comes from the developing world, where 82% of the world’s population live.

Blood is, of course, the red liquid that makes some of us faint when we see it. It delivers oxygen and vital nutrients, such as glucose, amino acids, and fatty acids, to our body's cells. It also carries away waste products, like carbon dioxide, from our cells to keep our body clean. Seven per cent of our body weight is blood. The average adult has about five litres of blood. Our heart pumps blood around our body at high speed. It travels through a system of arteries and veins, that reach every part of our body. Our blood is made up of red blood cells, white blood cells and platelets. When we cut ourselves, it is the job of platelets to clot the blood to stop us bleeding. We all have one of four different blood types. If we are given a different blood type, we’ll die.

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