0.5 mL serum or lithium-heparin plasma.
Ship in insulated container with freezer packs.
Collect blood into a red-top vacutainer; avoid hemolysis. Allow the sample to clot. Centrifuge the sample; separate the serum from the cells and transfer to a leakproof, labelled tube. Refrigerate or freeze and ship with freezer packs. Lithium-heparin plasma is acceptable, however laboratory reference intervals are for serum samples.