Why should tubes not be shaken vigorously after collection?

• A. It helps mix additives evenly
• B. It disinfects the sample
• C. It can cause hemolysis and affect lab results
• D. It ensures clotting

Answer: (C)

The key idea is that mechanical stress can damage cells in the blood sample. Shaking the tube vigorously creates a lot of force that can rupture red blood cells, a process called hemolysis. When cells break apart, their contents spill into the serum or plasma, which can falsely elevate or alter many test results—most notably potassium and various enzymes—and can interfere with optical tests. That kind of sample damage makes results unreliable and can lead to incorrect clinical decisions, or the lab may reject the sample and request a redraw.

To avoid this, tubes are gently inverted the recommended number of times to mix any additives evenly without breaking cells. The other statements don’t address this risk: disinfection is not achieved by shaking; vigorous shaking would not promote proper clotting; and while mixing additives evenly is a goal, it’s accomplished through gentle inversion rather than forceful shaking.