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Is blood ever blue?

Is blood ever blue?

Is blood ever blue?

Fact Frenzy tackles the question: Is blood ever blue?

Here come the facts!

Blood is red, inside your body and out. That is, unless you’re a Vulcan (fictional characters from Star Trek) then your blood may be green. But if you’re a human being from the planet earth, your blood runs through veins and arteries as red. However, there are variations of red, which this article will explain shortly…

One of the causes of misunderstanding might come from looking at your wrists (or other parts of your body where veins may be visible) — there are veins that appear blue. So of course, this must mean that the blood it carries is also blue, right?


Let’s begin to understand by distinguishing the difference between arteries and veins. Veins carry blood to the heart, and arteries carry blood away from the heart. Blood contains this fascinating stuff called “hemoglobin.” Hemoglobin is a type of protein that the blood uses to ferry around oxygen (among other uses). Think of it as O²’s Uber ride around the body. When it first leaves the lungs, hemoglobin is bound to the fresh intake of “oxygen passengers” and takes the form of oxyhemoglobin. This is what is known as “oxygenated blood” — which is a bright red — carried mostly by arteries, to the rest of the body. Veins, on the other hand (no pun intended), carry blood back to the heart. By this point, the hemoglobin has already dropped off its O² passengers. In fact, now those hemoglobin molecules are bound to CO² (carbon dioxide) molecules, taking the form of carbaminohemoglobin, a byproduct of metabolism.

Now, what color is carbaminohemoglobin? It is believed to be a bluish color, and may perhaps give oxygen-deprived tissue (such as veins, cold lips during hypothermia, etc.) a bluish color as well. But as a component of veinous blood, which has lower oxygen content (not depleted — living blood in mammals do not carry a “zero” amount of oxygen), it makes the blood take on a darker shade of red.

– Fact Frenzy

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