Which tube is typically used for chemistry and contains lithium heparin as an anticoagulant?

• A. Green top (heparin) or PST for plasma with gel
• B. Gray top
• C. Lavender top
• D. Light blue top

Answer: (A)

Chemistry testing benefits from a tube that prevents clotting while preserving the plasma for accurate measurements. The lithium heparin anticoagulant does exactly that, turning the blood into plasma without forming a clot. The standard green-top tube uses lithium heparin, and the plasma separator tube (PST) also uses lithium heparin and adds a gel barrier that, after centrifugation, keeps plasma cleanly separated from the cells. This combination yields rapid, stable plasma suitable for many chemistry assays.

Other tubes are aimed at different needs: gray tops contain a glycolysis inhibitor and an oxalate anticoagulant for glucose testing, not general chemistry; lavender tops use EDTA for hematology testing; light blue tops use sodium citrate for coagulation studies like PT and aPTT.