Two specimens required: One 7.5 mL serum separtor tube (SST), [also acceptable: One heparin plasma separator tube (PST)], and a single urine in a sterile plastic container. Refrigerate. NOTE: Specimens for testing both blood sodium and creatinine and random urine sodium and creatinine must be collected simultaneously. Serum and urine specimens can be collected within 24 hours of each other.
Centrifuge and separate serum or plasma from cells within 3 hours of collection and transport in original tube. Refrigerate.
2 mL serum or plasma and 25 mL urine.
0.5 mL serum or plasma and 5 mL urine.
Tubes other than those specified; urine and serum collected more than 24 hours apart.