When you give blood it takes about four to six weeks to replace the red blood cells removed from your donation. But where does that blood come from?

Your body is constantly replenishing its blood supply and creating new blood. Nearly a full pint of fresh blood is produced weekly, and almost all of it comes from the most unlikely of places — inside your own bones.

Blood is Produced in Bone Marrow 

Bone marrow is the key, with most of the blood being produced in “…the long bones in the arms, legs, back, and sternum. Bone marrow has yellow marrow, which contains fat, and red marrow, which contains hematopoietic (blood-forming) stem cells.” Wanda Lockwood - Which Part of the Body Makes Blood

Your bone marrow creates all the red blood cells, nearly all your white blood cells, and all of your platelets.

“Both the red and white blood cells arise through a series of complex, gradual, and successive transformations from primitive stem cells, which have the ability to form any of the precursors of a blood cell.” Science - Encyclopedia Britannica

Kidneys Play an Important Role 

But how does the body know when it’s running low on red blood cells? Oddly, it’s the kidneys that are designed to detect when oxygen is low and to send a message to the bone marrow to up the blood production. It’s a precise, constant communication inside your body, balanced to keep you running in optimum health. 

So next time you donate blood, remember you’re giving a “bone-fide” Gift of Life!