Why is glycolysis inhibition important in gray-top tubes used for glucose testing?

• A. To color code the sample
• B. To activate glycolysis
• C. To separate plasma
• D. It preserves glucose by inhibiting glycolysis

Answer: (D)

Preserving glucose by inhibiting glycolysis is essential because after blood is drawn, cells in the sample keep consuming glucose through glycolysis. If the sample isn’t processed promptly, the glucose level can drop, giving falsely low results. Gray-top tubes include sodium fluoride, a glycolysis inhibitor, which blocks the glycolytic enzymes and effectively stops glucose consumption, stabilizing the glucose concentration until analysis. The tube also contains an anticoagulant to prevent clotting, but the key purpose of the glycolysis inhibitor is to maintain an accurate glucose measurement. Coloring or separating plasma isn’t the goal here, and activating glycolysis would worsen accuracy.