My guess is that using player blood is a form of imprinting so the zombies will treat the player as their master.
The blood in the vacutainer has a reference to the type of creature it was drawn from stored in it, in the “corpse” field.
If you were going to check this, it would be something like:
if( my_vacutainer.contents.empty() ) {
add_msg( m_bad, _("The vacutainer is empty!") );
return;
}
if( my_vacutainer.contents[0].corpse->id == "human" ) {
// do cool stuff.
}
But a suggestion if you specifically want it to be the player’s blood, have it never make a blood item at all, just have it cause the effect of drawing the blood (damage, pain?) when you use it to either make some substance or revive the corpse.