Lavender-top tubes contain which additive and are typically used for which tests?

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Lavender-top tubes contain EDTA, which acts as an anticoagulant by binding calcium and preventing clotting. This preserves the morphology and integrity of blood cells, making EDTA ideal for hematology work where you need accurate cell counts and visual evaluation of cells. That’s why these tubes are used for a complete blood count and for blood smear evaluation—the goal is to keep the cells in their natural state long enough to count and examine them properly.

Other additives are used for different purposes: sodium fluoride in gray-top tubes inhibits glycolysis to preserve glucose, heparin in green-top tubes is convenient for many chemistry tests because it preserves plasma without clot formation for those analyses, and oxalate-containing tubes are also used for plasma tests where glycolysis inhibition and clot prevention are needed. But for CBC and smear evaluation, EDTA in lavender-top tubes is the standard choice.