The brown or red lumen is the largest lumen; use this to draw blood.

• A. The smallest lumen is brown or red; use to draw blood
• B. Color has no relation to lumen size
• C. The brown or red lumen is the largest lumen, use this to draw blood
• D. The brown lumen is only for medication administration

Answer: (C)

Understanding lumen color coding helps you pick the channel best suited for blood sampling from a multi-lumen catheter. The brown or red lumen is the largest, so using it for drawing blood provides the greatest flow, which helps avoid hemolysis and ensures an adequate, representative sample. A smaller lumen has more resistance, which can distort the sample or require more volume to get enough for testing. Color coding signals the lumen’s size and intended use, so selecting the largest lumen for blood draws is a safer, more reliable choice. Always follow your facility’s protocol about lumen use, verify that infusions or medications aren’t running in the lumen you’re using, and flush as required before and after drawing.