How long should plasma and cells be separated after collection to minimize glycolysis effects?

• A. 15 minutes
• B. 30 minutes
• C. 1 hour
• D. 2 hours

Answer: (C)

Glycolysis continues in blood after collection because the cells remaining in the sample keep metabolizing glucose. Separating plasma from cells quickly stops this ongoing metabolism, preserving the true glucose level. A practical window to minimize glycolysis is within about one hour of collection; within this time, glucose loss due to cellular metabolism is minimized compared with longer delays. Delaying beyond an hour allows more glycolysis to occur, leading to falsely low glucose readings. In practice, using glycolysis inhibitors and keeping the sample cooled can help, but the key idea is to separate the plasma from cells as soon as possible, ideally within one hour.