Jehovah's Witnesses are a Christian denomination with 7 million practicing members worldwide.
The group is well known for their door-to-door ministry, non-participation in politics (i.e. not voting), objection to war and military action, and refusal to accept blood transfusions.
Jehovah's Witnesses believe that blood is a sacred representation of life and that God forbids its use for purposes other than atonement for sin (sacrifice). They have thus forbidden their followers from eating meat from which the blood has not been drained, food products containing blood, and from receiving blood transfusions, regardless of its medical necessity and of the consequences to their life or health.
Specifically, they are directly forbidden from willingly accepting a transfusion of stored whole blood, red blood cells, white blood cells, platelets, and plasma, on penalty of excommunication and the threat of God's disfavor. Preoperative extraction followed by postoperative re-transfusion of their own blood is also banned, though certain intraoperative re-transfusion procedures are allowed.
They are directed to follow their own personal conscience in deciding to use other components of blood, or other products derived from or produced in blood (such as antivenins).
One of the controversial aspects of their refusal to accept blood transfusions is in that, against the advice of their doctors and surgeons, they often hold their critically ill minor children to the same rule, who are themselves not mature enough to decide to follow the belief willfully. In many cases a temporary guardian must be appointed by court order to make medical decisions for the child.
In some cases where parents actively prevent their child from being given a blood transfusion, usually through legal action but sometimes by leaving the hospital with their child before state guardianship can be ordered, proper care and treatment has been delayed or neglected. This has occasionally resulted in charges of negligence against the parents.