Blood is always red. Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red. Anyone who has donated blood or had their blood drawn by a nurse can attest that deoxygenated blood is dark red and not blue.
It's red because of the red blood cells (hemoglobin). Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn't change from red to blue. It changes from red to dark red.
Sometimes blood can look blue through our skin. Maybe you've heard that blood is blue in our veins because when headed back to the lungs, it lacks oxygen. But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion.
If you take oxygenated blood and leave it in the air it will turn dark red, then brown, then finally a bluish green from exposure to atmospheric oxygen.
Reasons That Veins Are Blue
The primary reason veins are blue is the way wavelengths of light hit the skin. White light can carry colors and waves with varying lengths. Red has the ability to travel the farthest. Violet waves are the shortest, and all the other colors fall somewhere in between.
It is a common myth that veins are blue because they carry deoxygenated blood. Blood in the human body is red regardless of how oxygen-rich it is, but the shade of red may vary. The level or amount of oxygen in the blood determines the hue of red.
Blood that has lost its oxygen is dark bluish-red. People whose blood is low in oxygen tend to have a bluish color to their skin. This condition is called cyanosis.
Blood is always red. Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red. Anyone who has donated blood or had their blood drawn by a nurse can attest that deoxygenated blood is dark red and not blue.
Oxygenated (arterial) blood is bright red, while dexoygenated (venous) blood is dark reddish-purple.
Darkened blood color is often observed in critically ill patients generally because of decreased oxygen saturation, but little is known about the other factors responsible for the color intensity. In addition, quantitative blood color examination has not been performed yet.
If the body receives deoxygenated blood or the lungs receive oxygenated blood, the heart will be strained or unable to meet oxygen demands in the body. Transposition of the great arteries is a congenital heart disease in which the aorta and pulmonary artery have been mismatched in their connection to the heart.
These observations may have led you to question the actual color of blood. So… is blood ever blue? Well, the quick answer is no, human blood is always red.
The arteries (red) carry oxygen and nutrients away from your heart, to your body's tissues. The veins (blue) take oxygen-poor blood back to the heart.
When hemoglobin releases oxygen, its shape is modified and appears darker red. Oxygenated or not, your blood is always red.
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.
It's normal to see period blood in shades of pink, red, and brown. The shades can mean different things. Pink blood: Pink blood is often seen at the time your period starts. At this stage, some of the fresh, bright red blood may mix with vaginal discharge causing the color to lighten and look pink.
Of the eight main blood types, people with Type O have the lowest risk for heart attacks and blood clots in the legs and lungs. This may be because people with other blood types have higher levels of certain clotting factors, which are proteins that cause blood to coagulate (solidify).
When we breathe in, the millions of air sacs in the lungs fill with fresh oxygenated air. The oxygen then moves into the blood by passing first through the very thin walls of the air sacs and then into the capillaries, which are tiny blood vessels in a network within the lungs.
Thin blood occurs when a person has a low number of platelets. Doctors refer to the condition as thrombocytopenia. The normal level of platelets in the blood is between 150,000–450,000 per milliliter (mL) . If levels of platelets fall below 150,000/mL , it may indicate thin blood.
Oxygenated blood has a high partial pressure of oxygen to deliver oxygen to the metabolizing tissues. Deoxygenated blood, on the other hand, has a low partial pressure of oxygen. The quantity of oxygen carried by each kind of blood is the primary distinction between oxygenated and deoxygenated blood.
Veins themselves are typically fairly colorless. So don't panic if your veins look a little bit blue, that's not uncommon. If however, your veins or arteries suddenly begin bulging or turning a dark color, those may be warning signs of underlying health conditions.
Dark-colored or blue veins are normal and healthy, although it can be a bit strange seeing sudden prominent blue veins pop up on your skin. Veins can become more visible due to various reasons, including decreased body fat, aging, genetics, physical activity, pregnancy, sun exposure, and certain medical conditions.
If you have pale skin it's not uncommon to see blue veins traveling across your arms, neck, chest and legs. In fact, visible veins that show through the skin's surface are just a part of life. But if you have big, blue, bulging veins you have varicose veins—and a red flag for vein health.