Watchtower Simplified Edition, September 2015, "Is Your Conscience a Reliable Guide:"
A branch office or the local congregation elders do not have the authority to make medical decisions for a Christian, even if he asks what to do. (Galatians 6:5) However, the elders can share what Jehovah says in order to help a Christian make a wise decision. For example, God has commanded us to keep abstaining from blood. (Acts 15:29) This command clearly helps a Christian to understand that he cannot accept medical treatments that involve taking in whole blood or any of its four major components.
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First question-- Where does the Bible say anything at all about the four major components of blood?