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My mom had blood drawn from her arm at the doctor's, and it looked black. What does it mean black blood? Thank you for the answer.
Question Date: 2016-11-03
Answer 1:

Great observation!

Human blood is red due to the presence of iron in hemoglobin, the protein in blood cells that allows the transportation of oxygen throughout the body. The color changes, however, depending on how much oxygen is in the blood.

If there is a lot of oxygen in the blood, it will appear bright red. This is common should blood be taken from an artery, which takes blood from the lungs to the rest of the body.

Deoxygenated blood is found in veins, which take blood from the body back to the lungs. Blood drawn from a vein will appear dark red or even black. So your mom probably had a doctor take blood from a vein. So the color is completely expected and normal given how our body’s circulatory system works.

While we are on the topic, there’s a persistent myth you might have heard that blood is actually blue until it encounters oxygen. People think this is the case because veins, when viewed through one’s skin, appear bluish. But this cannot make sense as blood transports oxygen and the red color comes from the iron. The bluish color of veins actually has to do how light is absorbed by skin. (Bonus fact: some organisms, like squids and crabs, do have blue blood!)

Thanks for the great question.

Answer 2:

There are a number of things that I can think of that it could be, and I am certain that your mom's doctor has a better idea of this than I would. I suggest you ask the doctor (or maybe just your mom after the doctor tells her if anything is wrong).

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