First of all, we’d like to state that Almighty Allah has blessed His servants by creating all kinds of provision on earth for them and He has permitted them to eat everything that is Halal (permissible) and good. Allah says: “O mankind! Eat of that which is lawful and wholesome in the earth, and follow not the footsteps of the devil. Lo! He is an open enemy for you.” (Al-Baqarah: 168)
However, Allah forbids a limited number of foods that are bad and can be detrimental to one’s health. It is the duty of every Muslim to seek what is Halal and keep away from Haram not only as regards food but also in all the other affairs of his life.
The Fiqh Council of North America states the following: “The verse 145 from Surat al-An`am which says: “Say: ‘I find not in the Message received by me by inspiration any (meat) forbidden to be eaten by one who wishes to eat it, unless it be dead meat, or blood poured forth, or the flesh of swine – for it is an abomination – or what is impious, (meat) on which a name has been invoked other than Allah’s.’ But (even so), if a person is forced by necessity, without willful disobedience, nor transgressing due limits, thy Lord is Oft-Forgiving, Most Merciful.”
The “poured out blood” in this verse means the flowing and running one, which flows from the vein after slaughtering an animal. This shows that the prohibited kind of blood is the streaming, liquid one and it does not include the liver or the spleen because they are congealed, and the Prophet, peace and blessings be upon him, said: “Two dead animals and two kinds of blood have been permitted for us to eat, fish and locusts, the liver and the spleen.” Also, this does not include the rest of the blood which remains in the vein after the slaughter, because none of these are flowing.
The reason why the streaming blood is prohibited is the fact that the blood is the medium of transmitting a lot of the diseases and it is a suitable environment for microbes and bacterium to multiply, that is why Islam orders us to slaughter livestock from the jugulars vein and let the blood flows.”