Which Vacutainer Tube Has No Additive?

Which Vacutainer Tube Has No Additive? 6. Red – Tube contains no additive, used for serum chemistry testing, serology, and blood bank testing. Do all tubes have additives? Most blood collection tubes contain an additive that either accelerates clotting of the blood (clot activator) or prevents the blood from clotting (anticoagulant). Which tube or tubes