Glycolytic Inhibitors and Glucose Stabilization
When blood is removed from the body, the living cells (especially red blood cells) continue to consume the glucose present in the sample through a process called glycolysis. If a sample is left at room temperature, glucose levels can drop by approximately 5% to 10% per hour. To obtain an accurate blood sugar reading, this process must be stopped.
Gray-top tubes contain Sodium Fluoride, a glycolytic inhibitor. It works by poisoning the enzymes in the red blood cells that break down sugar, effectively "freezing" the glucose level at the moment of collection. These tubes often also contain Potassium Oxalate, which acts as an anticoagulant. This combination is essential for diabetes screening and tolerance tests where precise glucose measurements are the primary diagnostic goal.