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What color top tube contains the anticoagulant heparin?

Red

Green

The presence of heparin as an anticoagulant is what makes the green top tube distinct among the various types of vacuum tubes used in blood collection. Heparin works by inhibiting thrombin, an enzyme integral to the blood clotting process. This anticoagulation prevents the formation of clots in the blood sample, which is essential for certain types of blood tests that require plasma instead of serum.

Green top tubes are typically used for tests that require plasma analysis, such as metabolic panels or certain hormone tests. The color coding of blood collection tubes helps to quickly identify their contents and the appropriate tests for which they should be used. Other colors, such as red, blue, or purple, contain different additives—such as no anticoagulants, sodium citrate, or EDTA respectively—serving a variety of other testing needs but not for those that require heparin as an anticoagulant.

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Blue

Purple

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