Religious beliefs about blood

Judaism
In Judaism, blood cannot be consumed even in the smallest quantity (Leviticus 3:17 and elsewhere); this is reflected in the dietary laws. Blood is purged from meat by salting and pickling.

Other rituals involving blood are the covering of the blood of fowl and game after slaughtering (Leviticus 17:13); the reason given by the Torah is: "Because the life of every animal is [in] his blood" (ibid 17:14), although from its context in Leviticus 3:17 it would appear that blood cannot be consumed because it is to be used in the sacrificial service (known as the korbanot), in the Temple in Jerusalem.

Ironically, Judaism has historically been the religion to be most affected by blood libels.

Christianity
Christians believe that the Eucharist wine is, or represents, the blood of Jesus. This belief is rooted in the Last Supper as written in the four gospels of the Bible, in which Jesus stated to his disciples that the bread which they ate was his body, and the wine his blood. ''"This cup is the new testament in my blood, which is shed for you." (Luke 22:20, KJV)''. The accepted Christian belief is that Jesus' blood atoned for the sins of the people.

Jehovah's Witnesses
Jehovah's Witnesses are prohibited from eating blood and accepting tranfusions of whole blood or any of red cells, white cells, platelets or plasma. They are permitted to accept fractions, and the acute normovolemic hemodilution (ANH) and autologous blood salvage (cell saver) procedures.