Q. Do sodium citrate tubes clot?

Common causes of blood clots in sample tubes include improper mixing of the sample with the clotting agent in the tube or clotting of the sample while in transit. No danger or health issue is indicated. Sodium citrate an anticoagulant that chelates calcium is poured into the coagulation tubes (blue top) to prevent blood from clotting. Calcium has a critical role in the coagulation process. Laboratory coagulation assays require the addition of calcium so that clots can form. Because of the unpredictable nature of biological samples it's conceivable that tests won't be able to be analyzed.