Lithium Heparin / Green Vacutainer.

These are the green-top tubes, widely used for biochemistry tests because they prevent clotting without interfering much with analytes. Key details: Additive: Lithium heparin Action: Inhibits thrombin → prevents clot formation Sample type: Plasma Mixing: Gently invert 5–8 times Common tests: Routine biochemistry (Urea, Creatinine, LFTs, Electrolytes*) Cardiac markers (Troponin, CK-MB) CRP, Procalcitonin Ammonia (urgent samples) Blood gases (specific heparinized tubes)