Urban Myth or Truth: human blood is blue when inside the body and turns red only when it reacts with air?

I am absolutely staggered by the number of people who actually believe that deoxygenated blood is blue. No, human blood is *never* blue. Even when totally depleted of oxygen, it becomes a dark red colour (some might call it maroon). If you were to see a car or a paint strip that colour, you would say it was red. Fully oxygenated (arterial) blood is bright red. Depleted (venous) blood is dark red. NOT blue. The only time blood is ever blue is in mollusks and some arthropods, which utilize copper in the molecule that carries oxygen to the their tissues (hemocyanin), instead of iron as vertebrates do (hemoglobin). The veins through your skin only look blue because of diffusion of the light while passing through layers of tissue. In actuality, they're more of a greyish, white colour. You don't normally see arteries through the skin because they tend to be buried deeper in the tissues, but they're pretty much the same colour (but thicker walled, with higher blood pressure). The idea that human blood is blue is absolutely a myth.

Myth, it's always red. It goes a darker red, purple-like (Some call it blue) when starved of Oxygen.

It's a myth. Veins in the skin appear blue for a variety of reasons only weakly dependent on the colour of the blood. Light scattering in the skin, and the visual processing of colour play roles as well. blood is continuously red ranging from bright red when oxidised to dark red when free of oxygen.

Blood is a specialized bodily fluid (technically a tissue) that is composed of a liquid called blood plasma and blood cells suspended within the plasma. The blood cells present in blood are red blood cells (also called RBCs or erythrocytes), white blood cells (including both leukocytes and lymphocytes) and platelets (also called thrombocytes). Plasma is predominantly water containing dissolved proteins, salts and many other substances; and makes up about 55% of blood by volume. Mammals have red blood, which is bright red when oxygenated, due to hemoglobin. Hint: if homo sapiens are reptiles what color would their blood be? I should know.I'm a vampire. Bloody hell!

its a myth. blood is red. veins are blue

Untrue

That's a myth. Human blood is NEVER blue! There may be instances when it could have a slight blueish tint, but blood is ALWAYS red.

This is a myth. Human blood is always red, the bluish color that one sees looking at a blood vessel is from the tissues around it. The blue and red colors are used to represent veins and arteries respectively, to make it easier to visualize in a diagram, but the blood in those veins is still a red color.

I always thought that it was true that blood became red after it reacted with air, and it was blue inside the body. My wife just took an anatomy and physiology class (she's studying to be a nurse) and she just told me the other day that it was a myth. She said the reason why people think it is blue is because of the color of the veins. So don't believe anyone who is telling you different.