How long should the centrifuge spin after blood collection?

• A. 5 minutes
• B. 15 minutes
• C. 30 minutes
• D. 60 minutes

Answer: (B)

The key idea is to give enough time for the blood to separate into serum (or plasma) and the solid components so you have a clear liquid to test. About 15 minutes at the appropriate moderate centrifugal force is typically used because it reliably yields a clean, separated sample without leaving residual clot or cells in the serum. If you spin for less than that, clot fragments or cells can remain in the liquid, potentially skewing test results. Spinning longer doesn’t generally improve separation and can unnecessarily delay processing or risk sample integrity in some setups. So, 15 minutes is the standard balance to achieve proper separation for routine serum testing.