the authority here is internal rather than external.....but not an actual command.
"......and from fornication." 1Cor 5:11, Ephesians 5:5 (command)
"abstain" to keep or prevent yourself from doing....
Blood is not a finite act though and neither are "things strangled" or sacrificed to idols. It is understood that you do not ride a dead chicken same as you do not eat boats.
Simply put, to abstain from alcohol means ( Except when a skin doctor wants to use the word abstain in a peculiar way meaning not to apply it.) that you do not consume it. To what degree? A patient should be abstaining from spirits when he drinks a small diluted amount.
We abstain from acts done in connection with objects and those acts are determined by the context.
In reference to the Bible, you need context to understand what abstain from blood means? What do you think the Bible author means? In connection with the related verse, it's ok to put a gallon of blood into your body?
It would seem that the author of the Bible would want the reader to clearly understand what is required of him when he demands compliance from the reader, but the Bible is written in a peculiar way, and at times a word or a verse or more alludes to something more than the context, and the only way to know what it means is to ask the author to elaborate.