Critics say their is a big difference between the Bible's prohibition on eating blood and having a blood transfusion to save a life.
First of all eating blood is an option. The ancient law required Israelites to drain the blood before eating the meat. The requirement was not a life or death matter. Even when people were weak and hungry as described in 1 Samuel 14:31-35 it is unlikely they would have died if they took the time to drain the blood out of the animals they ate.
Secondly when the Bible says to 'abstain from blood' it clearly was talking about eating blood, not blood transfusions. Acts 15:28-29. Ancient people were not able to do blood transfusions and most likely didn't think such a thing was possible.
The Bible says blood represents the sacredness of life. Abstaining from blood meant ancient people would drain the blood out of animals before eating them. The Bible was not referring to blood transfusions that has saved countless lives in modern times. The Bible was referring to eating blood.
Is this what the Bible meant? Of course not. The Bible does not recommend that we kill ourselves. We are not required to abstain from having blood in our veins. The Bible simply says we're not to put blood in our stomachs.
If you lose blood due to an accident or the need arises for emergency surgery, it makes sense to put blood back where it belongs. In this way we are good stewards of the life God gave us.
By doing what we can to prolong life we are appreciating God's gift of life. We are taking care of the most valuable possession God gave us, - our health. By refusing a blood transfusion when we need it, critics say we are disrespecting God's gift of life.
Since life is sacred according to the Bible, it makes sense that reasonable persons would welcome all proven medical procedures that saves lives. Since we cannot survive without blood and we cannot abstain from having blood in our body, it makes sense that we would take advantage blood transfusions when necessary.
Some may object and say that if blood represents the life of a human or animal it would be wrong for us to put someone else's life in our body. There is some logic to this theory. Most of us don't want someone else's bodily fluids to get mixed up with ours. e.g. we don't normally share the same drinking glass with strangers. Why would we want to put their blood inside our body?
Normally we would never want a blood transfusion. It's not a fun thing to do on the weekend. Blood transfusions are reserved for life and death situations. For most people the need for a blood transfusion is rare. But in critical situations where there are no other options, blood transfusions can save lives.