In the standard order of draw, which color tube is drawn second?

• A. Red
• B. Green
• C. Light Blue
• D. Yellow

Answer: (C)

In venipuncture, the order of draw is chosen to keep each tube’s additive from contaminating the others and to protect tests that need a precise sample. The second tube in the sequence is the light blue top, which contains sodium citrate used for coagulation studies. Drawing it second helps ensure the citrate-to-blood ratio remains accurate and minimizes carryover from the first tube, which is usually a yellow top for sterile blood cultures and must stay free of additives. If other additive-containing tubes were drawn first, traces of those additives could contaminate the citrate tube and compromise tests like PT and aPTT. The remaining colors (red, green, etc.) come later because they involve different additives or serum separation. So the light blue tube is drawn second.