They are as safe as many other medical practices. There is always a risk, and more so when blood from others is involved. Transplants and blood transfusions are put off as much as possible and the family is considered first. The blood is tested as much as it can be for illness.
As with anything there are various inherent risks. As with blood transfusions there is a risk factor to getting one. Although science has tried to minimize the risks there still are a few. You could have an allergic reaction for which the doctor could prescribe medicine. You could risk a iron overload, contract a virus or infectious disease. Personally I feel the risks outweigh the alternative.
I believe that blood transfusion procedures are safe. Generally the blood is collected from people after meeting certain criteria, so the blood itself is safe. Secondly, the procedures are always overseen by a physician and these procedures have been done over and over again. I would feel safe receiving a blood transfusion.
I think blood transfusion procedures are safe and have a chance of harm. I think most doctors and nurses know what they are doing and have a good hold on things, but I do think that everything comes with a certain degree of risk and has a chance to harm the person.
The history of blood transfusions is riddled with scary stories involving death and disease. These days the benefits outweigh the risks. Extreme stories that come out in the news of improper care and testing on blood that is used are one in a million. You can confidently trust in blood transfusions.
As regards Genesis 9:4, the Society teaches that this refers to a prohibition on eating blood which applies to all mankind, Jew or Gentile.[9,10] It seems that the verse is referring to the eating of animals which have been killed without being bled. Also the very use of the word lifeblood (NIV) emphasises the close relationship between blood and life. Throughout history many pagans believed that by eating life that is `in the blood (Lv 17:11 ) they could increase their own life-force. This verse serves to correct that misconception and to remind us that life is the precious and mysterious gift of God: 'Just as I gave you the green plants, I now give you everything'. (Gn 9:3).