According to Leviticus 7:26-27 Jews shouldn't consume blood. So why can Jews accept blood transfusions in non-life threatening situations? Is the act of inserting blood via arm not considered "consuming."
Human blood is not included in the prohibition (Shulchan Arukh YD 66:10). There is a concern when consuming any permitted blood that no one think you are consuming forbidden blood. A classic solution to this is including fish scales in a cup of fish blood (ibid. :9). It seems to me that a transfusion bag serves this purpose sufficiently. Even were one to argue on this point the prohibition would remain at a rabbinic one and not a biblical one, and hence can be lifted for any seriously ill individual even if their life is not threatened.
Additionally, one is only prohibited from consuming forbidden food through the throat (Rambam MA 14:3).
That verse in Leviticus says don't eat blood. It doesn't say not to inject it.