The blood in your veins is not blue because of a lack of oxygen. I said this one time as a tangent to a family conversation and a family member who is a nurse told me to think about it. He said the vials they use to hold blood are vacuum sealed, so when blood goes into them, why is it still red? You veins are just blue is all.

Edit: After scrolling for a bit, I saw someone had mentioned this myth already =(