Phlebotomy stopper colors indicate what tests a technician conducts on the blood within and the presence of any additives inside the tube, according to the Department of Pathology at Dartmouth-Hitchcock Medical Center. The stopper color also tells phlebotomists in which order to fill the vials during a blood draw to prevent cross contamination.
A vial with a red stopper does not contain an anticoagulant or clot activator, while a vial with a gold stopper contains silicon gel and a clot activator, explains Dartmouth-Hitchcock Medical Center. A vial with a light blue stopper contains the anticoagulant sodium citrate and contains blood used for coagulation studies. The phlebotomist must fill this light blue vial completely to maintain the correct ratio of anticoagulant to blood.
Vials with royal blue stoppers may contain sodium heparin or may be empty, states the Dartmouth-Hitchcock Medical Center. Technicians use these vials to contain blood for specific drug and heavy metals testing. Whether or not the vial contains sodium heparin also affects the blood draw order as specified by the National Committee for Laboratory Standards.
Green-stoppered vials contain lithium heparin, while bottles with a lavender stopper hold the anticoagulant K2EDTA, notes the Dartmouth-Hitchcock Medical Center. Technicians use gray-stoppered vials for glucose testing because these vials hold sodium fluoride and potassium oxalate to constrain glycolysis. Vials with yellow stoppers hold a anticoagulant solution, and technicians use them for DNA testing.