Venous blood is a deoxygenated blood which runs in the veins from our organs towards the heart. Then it runs in the pulmonary arteries and then to the lungs. This blood is different from the arterial blood. Arterial blood is oxygenated whereas the venous blood is deoxygenated. The concentration of glucose is very low in venous blood and a lower pH as compared to the arterial blood. It is usually warmer than the arterial blood. Venous blood has a high concentration of waste products such as urea.

The venous blood can be attained by a small procedure known as venipuncture which is also known as phlebotomy. Most of the tests which are done in laboratory are done with the venous blood with the exclusion of the arterial blood gas. The color of the venous blood is dark red. As we see our skin we can easily see some veins which are blue, purple or green in color but actually the color of blood is dark red. It is seen in different colors due to the opaque skin. The color of the arterial blood is bright red.

The color different between the arterial blood and venous blood is due to the difference between deoxygenated blood and oxygenated blood. The number of deoxyhemoglobin and oxyhemoglobin is also different in both bloods due to which there is a color difference. You can understand this thing easily by this example that if you draw out some blood for medical test then the blood will be dark red but if you expose that blood in front of oxygen then the color will be bright red like the arterial blood.