- The average human body has about 1.3 gallons (5 L) of blood
- It accounts for 7% of total body weight
- Veins are large blood vessels carrying deoxygenated blood to the lungs. The lungs oxygenate the blood with oxygen from the air. Then, the blood goes into arteries….
Lemme also add that if you ever want to get a sense of how much two liters of blood actually is (the point at which your character is going unconscious and possibly dying), take a soda bottle, fill it with water, add a few drops of red food coloring, and then upend the whole thing on a floor or patio somewhere (NOT where water can be absorbed though; try the bathtub). You will likely be shocked by how much fluid that actually is. You will wonder where we put it all. Do the same with a cup, a pint, a liter. You’ll get a much better feel for how much blood you’ve actually seen people lose in the past from various injuries you’ve experienced/witnessed, and you’ll write about it more accurately in your own stories. (Not that your characters often need to know the measure of how much blood another character has lost, but this is the technique my EMT instructor used to show my class how to more accurately estimate blood loss.)