What is the purpose of color coding the tops of blood collection tubes?

The system of blood collection in evacuated tubes for a variety of laboratory tests is known to consist of many tubes with color-coded tips that indicate the tube contents. The colors of the caps of blood collection tubes inform technicians about the tube additives, additive functions, and laboratory tests that are necessary. The majority of blood collection tubes are responsible for storing chemicals that can either accelerate or prevent blood coagulation.

An evacuated blood collection tube is a sterile plastic or glass test tube used to collect blood specimens. It includes a colored rubber stopper that produces a vacuum seal inside the tube, allowing it to pull a predetermined volume of liquid. To stabilize and maintain the blood sample prior to analytical testing, blood collection tubes may contain chemicals.

Each evacuated blood collection tube has a color-coded plastic or rubber cap. The color indicates the sort of additives contained in the tube. Chemical chemicals such as anticoagulants that preserve blood for laboratory processing are examples of additives. Some tubes additionally contain a gel with the density of blood cells or serum. When these gel-containing tubes are centrifuged, the blood cells fall to the bottom and the serum gathers on top, separated by a layer of gel. When plasma, rather than serum, is required for lab analysis, evacuated blood collection tubes that do not include gel or a clotting agent are employed.

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Color	Item	Additive	Usage
Red	Plain tube	No	Clinical Biochemistry,Immunology and serology test
Red	Pro-coagulation tube	Clot activator
Yellow	Gel&Clot Activator tube	Gel&Coagulant
Purple	EDTA tube	EDTA K2/K3	Blood routine examination
Black	ESR tube	3.8% Sodium Citrate	ESR test
Blue	Coagulation tube	3.2% Sodium Citrate	Coagulation function test
Green	Heparin tube	Sodium Heparin/Lithium Heparin	Clinical chemistry for emergency treatement, Blood rheology test
Grey	Glucose tube	Sodium Fluoride & Sodium Heparin/ Sodium Fluoride&EDTA/ Sodium Fluoride&Potassium Oxalate	Glucose and Lactate test

Each additive serves a distinct purpose and is chosen based on the laboratory test to be performed. The color markers on the tubes assist the phlebotomist in determining which tube should be used to draw blood in line with the prescribed test. Because blood collection tubes and tests are linked, selecting the incorrect color tube may render the blood sample ineligible for the intended test.