Keritot 20 - Consuming Blood
It is certainly forbidden to consume blood, but "lifeblood" carries with it the penalty of being cut off from the spiritual source, while regular blood is prohibited by a negative commandment. In addition, "blood" of some creatures is permitted. What are the exact circumstances?
If one consumed blood which came as a result of slaughter, whether of kosher domesticated or non-domesticated animals, fowl, or non-kosher animals, this is lifeblood. So too if he tore the animal's pipes, or did bloodletting in which the soul departs. Blood of the spleen, blood of the heart - although these organs are full of blood, and so too the blood that drains gently after the animal is slaughtered - one is not liable to be cut off for these, although it is prohibited. Thus only blood of animals and fowl is prohibited, but not blood of grasshoppers, or of fish.
Art: Elias van den Broeck - A Bouquet of Roses, Morning Glory and Hazelnuts with Grasshoppers, Stag Beetle and Lizard