Which type of tube is specifically used for collecting specimens for blood glucose testing?

The gray top tube is specifically designed for collecting specimens for blood glucose testing due to its unique additive, which is sodium fluoride. Sodium fluoride acts as a glycolytic inhibitor, meaning it prevents the breakdown of glucose by cells in the blood sample. This preservation of glucose levels ensures more accurate testing results, especially when there might be a delay in processing the sample.

In contrast, the other tubes mentioned do not contain this necessary additive for glucose preservation. The red top tube generally has no additives and is used for serum testing, the green top tube contains heparin as an anticoagulant for plasma determinations, and the blue top tube has sodium citrate, which is primarily used for coagulation studies. Therefore, the gray top tube is the appropriate choice for accurately measuring blood glucose levels.