Final answer:
Gray tubes typically preserve blood glucose levels for 24 to 48 hours at room temperature due to the presence of sodium fluoride and potassium oxalate, which inhibit glycolysis.
Step-by-step explanation:
Gray tubes used for collecting blood specimens are specifically designed for glucose testing and contain preservatives such as sodium fluoride and potassium oxalate. These additives prevent glycolysis, which is the process where glucose is consumed by cells in the blood. The sodium fluoride acts as a glycolysis inhibitor, ensuring the stabilization of glucose levels. Thus, when asking about how long gray tubes preserve blood specimens, it generally refers to glucose stability. Typically, these gray tubes can preserve blood glucose levels for 24 to 48 hours when stored at room temperature. This period can be extended if the tubes are refrigerated, allowing for more accurate results in glucose measurement during that timeframe.