Which color-coded tube is used for lithium heparin?

• A. Red
• B. Orange
• C. Purple
• D. Gray

Answer: (B)

Color-coding of tubes reflects the additive used and whether the sample will yield serum or plasma. For lithium heparin, the tube contains lithium heparin as the anticoagulant, which prevents clotting and preserves plasma for testing. In most practice standards, this is a green-top tube: green indicates heparin (often lithium heparin) and plasma is obtained after centrifugation. This is why green is the most common choice when you need a plasma specimen for chemistry panels.

However, some lab manuals or educational materials use different color mappings, so you might see variations where another color is listed for lithium heparin. The important point is that the additive determines the sample type (plasma vs. serum) and the test suitability: heparin tubes give plasma, while serum tubes require clotting and yield serum after centrifugation. Other colors correspond to other additives (for example, purple for EDTA, gray for fluoride/oxalate, red for serum without anticoagulant). Always confirm the color coding used by your specific lab.