Don’t get excited, though. If you scraped together every bit of gold in the human body, the amount would be smaller than a single grain of sand.
If you get a cut, blood will swarm to the injury. Then that blood will begin to thicken into a clot that stops the bleeding, almost as if by magic.
Perhaps the coolest thing about the red stuff is that the human body is always making new blood to replace the old. You can thank your bones for that. Marrow, or the spongy tissue inside the body’s biggest bones, is like a blood-building factory.
“The average person has 8 to 12 pints of blood in their body, depending on how big they are,” says Rodney Wilson, a communications specialist with the American Red Cross National Headquarters in Washington.
That applies to kids, too. Even though children are much smaller than adults, by the time you are 5 or 6 years old, you’ve got basically as much blood as you’ll ever have.
Best of all, since your veins are full of the stuff, and because the body keeps making more, one person can give their blood to someone else in need. The process usually takes 10 minutes, says Wilson, and other than a small pinch of a needle at the beginning, it’s almost painless.
Donated blood can help people with many types of medical issues, including victims of car accidents, women who have just had a baby and those who are undergoing treatment for cancer.
“Statistics show that 97 percent of us know someone who has received a blood transfusion, even if we don’t realize it,” says Wilson.
In most places, you have to be at least 17 years old to donate blood, though some states allow 16-year-olds to give if they have permission from their parent or guardian. Becoming a blood donor can also help you find out your own blood type. Humans have four general types — A, B, AB and O — each of which corresponds to the structure of the red blood cells you inherited from your parents. In addition, each of those types can be “positive” or “negative,” depending on the presence (+) or absence (-) of a protein called the Rhesus, or Rh, factor.
If that’s starting to get confusing, don’t worry. There’s really only one thing you need to remember about becoming a blood donor.
“Blood donation helps save lives,” says Wilson. “It’s an easy way that you can be a hero.”
In honor of World Blood Donor Day, ask the adults in your life if they’ve ever donated blood. Maybe when you’re old enough, you might consider becoming a superhero blood donor, too.
Bittel is a freelance journalist who often writes about animals. His latest children’s book is “How to Talk to a Tiger . . . and Other Animals.”