Short answer
No. The blood left in the meat and veins of a properly slaughtered animal, including the red juice that comes out of chicken or beef while cooking, is not najis, and the meat is fine to eat. What is impure is blood that flowed out at the time of slaughter. The four schools agree in substance.
Only flowing blood (dam masfuh) is najis. Blood that stays in the meat, veins, heart, liver and spleen after a proper slaughter is pure. Pink or red liquid from meat while thawing or cooking is pure. Flowing blood that has stuck to the outside of the meat should be washed off.
The four schools agree on this.
Explanation
The Quran forbids "blood spilled out", meaning blood that pours out of an animal when it is killed. Scholars take the description seriously: the blood that drains at slaughter is impure and haram to consume, while the small amount that stays in the flesh after proper draining is neither. Aisha is reported to have said that they used to cook meat and see streaks of blood in the pot, and they ate it.
In practice, for a Hanafi:
- Red juice from chicken or beef when you cook or thaw it: pure. It is mostly water and muscle protein, and in any case it is not flowing blood from slaughter.
- Pink meat, rare steak, red bones in chicken: pure and halal if the animal is halal and slaughtered properly.
- Liver and spleen: pure and halal; a well-known report counts them as the two permitted bloods.
- Clots or blood on the cut surface from the slaughter: wash them off before cooking.
- Juice on your clothes from cooking: no need to wash it for prayer, though you may for cleanliness.
- Fish blood: pure in the Hanafi school.
Washing meat before cooking is a common habit and is fine, but it is not required to remove the blood that stays inside. Soaking meat for hours to drain it is not required either.
Human blood is a separate matter: blood that flows from a wound is najis and breaks wudu in the Hanafi school. See bleeding and wudu and blood on clothes. Whether the meat itself is halal depends on the animal and the slaughter: see is it halal.
The evidence
Quran, Surah Al-An'aam 6:145
قُل لَّآ أَجِدُ فِى مَآ أُوحِىَ إِلَىَّ مُحَرَّمًا عَلَىٰ طَاعِمٍۢ يَطْعَمُهُۥٓ إِلَّآ أَن يَكُونَ مَيْتَةً أَوْ دَمًۭا مَّسْفُوحًا أَوْ لَحْمَ خِنزِيرٍۢ فَإِنَّهُۥ رِجْسٌ أَوْ فِسْقًا أُهِلَّ لِغَيْرِ ٱللَّهِ بِهِۦ ۚ فَمَنِ ٱضْطُرَّ غَيْرَ بَاغٍۢ وَلَا عَادٍۢ فَإِنَّ رَبَّكَ غَفُورٌۭ رَّحِيمٌۭ ﴿١٤٥﴾
Say, "I do not find within that which was revealed to me [anything] forbidden to one who would eat it unless it be a dead animal or blood spilled out or the flesh of swine - for indeed, it is impure - or it be [that slaughtered in] disobedience, dedicated to other than Allah. But whoever is forced [by necessity], neither desiring [it] nor transgressing [its limit], then indeed, your Lord is Forgiving and Merciful."
Only blood that pours out is forbidden and impure, not the blood left in meat.
Where the ruling is recorded
- al-Durr al-Mukhtar with Radd al-Muhtar, Kitab al-Taharah, chapter on najasat. Blood remaining in the meat and veins after slaughter is pure.
- al-Hidaya, Kitab al-Taharat, chapter on najasat. Flowing blood is najasah ghalizah.
- al-Mughni (Ibn Qudama), Kitab al-At'imah, on blood remaining in meat. The blood left in the flesh after slaughter is excused.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.