Do you have to take bcaa supplement on a empty stomach or can you take it with a meal? will taking it with a meal diminish its absorption and effects?

Better without prot.: Because Amino Acids compete with one another for uptake, bcaa's will be more fully absorbed if you don't eat much other protein with it- you could have some fruit ; veggies or starches with it and that would not reduce absorption. Even if you take it with a protein-rich meal much will still be absorbed, but for maximum benefits take without much other protein.