# color of blood **URL:** \ **Category:** Factual Questions\ **Created:** [January 23, 2001, 8:18pm UTC](https://boards.straightdope.com/t/color-of-blood/51449 "2001-01-23T20:18:06Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\ **Post date:** [January 23, 2001, 8:18pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/1 "2001-01-23T20:18:06Z")
Is your blood blue before it comes gushing out? If not then why are your veins blue? ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [January 23, 2001, 8:22pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/2 "2001-01-23T20:22:18Z")
Yes, it’s blue. Oxygen in the blood makes it red; the blue stuff is on its way back to the lungs to pick up more. On contact with air, it sucks up the oxygen so fast you can’t see the blue part. Researchers withdrew some blood from Frank Shorter while he was running on a treadmill; it was black, there was so little oxygen left in it. ---
**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\ **Post date:** [January 23, 2001, 8:29pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/3 "2001-01-23T20:29:33Z")
then why is it red when they withdraw a tube full for a blood test? ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [January 23, 2001, 8:54pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/4 "2001-01-23T20:54:38Z")
Blood in the arteries is bright red. Blood in the veins is dark red. Veins look blue because the skin absorbs most of the red light. Mailbag item: [If blood is red why do your veins look blue?](http://www.straightdope.com/mailbag/mbloodrd.html) ---
**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\ **Post date:** [January 23, 2001, 8:54pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/5 "2001-01-23T20:54:47Z")
also why cant you look at your skin and tell the difference between veins and arteries? wouldnt the veins be blue and the arteries red? ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [January 23, 2001, 8:55pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/6 "2001-01-23T20:55:13Z")
Here’s a column. It’s different shades of red. > [@](#): > > Blood is a bright red in its oxygenated form (i.e., leaving the lungs), when hemoglobin is bound to oxygen to form oxyhemoglobin. It’s a dark red in its deoxygenated form (i.e., returning to the lungs), when hemoglobin is bound to carbon dioxide to form carboxyhemoglobin. > Veins appear blue because light, penetrating the skin, is absorbed and reflected back to the eye. Since only the higher energy wavelengths can do this (lower energy wavelengths just don’t have the _oomph_), only higher energy wavelengths are seen. And higher energy wavelengths are what we call “blue.” ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [January 23, 2001, 8:57pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/7 "2001-01-23T20:57:27Z")
Darn simulpost. But then again, it answers your third question too. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [January 23, 2001, 9:02pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/8 "2001-01-23T21:02:06Z")
> [@](#): > > \*Originally posted by justinh \* > then why is it red when they withdraw a tube full for a blood test? If it’s red, then they’re drawing it from an artery, not a vein. Arteries carry oxygenated blood from the lungs, (with one expection) and veins carry deoxygenated blood to the lungs (with one exception.) ---
**Author:** ![Spritle](https://avatars.discourse-cdn.com/v4/letter/s/5daacb/32.png) [@Spritle](https://boards.straightdope.com/u/Spritle)\ **Post date:** [January 23, 2001, 9:39pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/9 "2001-01-23T21:39:58Z")
Arteries are more important than veins in terms of what your body needs - oxygenated blood. For this reason, they are more protected, lying deep within the body, usually near bones. It is tough to withdraw blood from an artery with a needle and syringe. Veins return blood. They lie near the surface. This is where _most_ blood is drawn. If you have blood drawn from the inside of your elbow or back of hand, it is from a vein. Blood in arteries is bright red from the oxygenation. Blood in veins is dark red from lack of oxygenation. ---
**Author:** ![Sattua](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sattua/32/11906_2.png) [@Sattua](https://boards.straightdope.com/u/Sattua)\ **Post date:** [January 23, 2001, 11:09pm UTC](https://boards.straightdope.com/t/color-of-blood/51449/10 "2001-01-23T23:09:09Z")
Also, the walls of arteries tend to be thicker and more opaque than those of veins, which makes them harder to see under the skin.