One 7.5 mL serum separator tube (SST). Fasting specimen recommended. Also acceptable: One 5 mL red top tube or 4 mL green top tube (heparin).
Allow to clot, centrifuge and separate serum or plasma from cells within 2 hours. Vitamin B12 is a light-sensitive analyte; protect specimen from light. Refrigerate. Freeze if specimen will not be assayed within 48 hours of collection. If specimen is frozen, send a separate specimen if additional testing is ordered. Allow no more than one freeze/thaw cycle.
48 hours refrigerated or 30 days frozen.
0.5 mL serum or heparinized plasma.
200 µL serum or heparinized plasma.
Refrigerated, or frozen on dry.
Moderate to gross hemolysis; EDTA specimen; specimen frozen/thawed more than once.