* OSMOLALITY, BLOOD Mnemonic OSMO Synonym Osmotic Concentration - OSMO Specimen Collection Requirements Collect Serum or Plasma, one 5.0 mL gold (SST), 7.0 mL red or 3.0 mL mint green (lithium heparin, PST) top tube Handling Allow serum to clot completely at room temperature (minimum – SST: 30 minutes and red top tubes: 60 minutes). Specimens must be centrifuged and removed from cells within 24 hours. Preferred Volume 1.0 mL Serum/Plasma Minimum Volume 0.25 mL Serum/Plasma (0.60 mL minimum whole blood draw) Transport Refrigerated (2-8°C) Stability AFTER SEPARATION FROM CELLS: Room Temperature (18-26°C): 24 hours; Refrigerated (2-8°C): 48 hours; Frozen (≤ -20°C): 2 weeks Testing Information Performed 7 days/week Reported 24 hours Method Osmometry (Freezing Point Depression) Reference Values Reference Values Serum: 275-300 mOsm/Kg CPT Codes 83930 Last Updated: Tuesday, April 30, 2019 04:50:13 PM Client Services: 503-413-1234