What blood tube color is for which test

2025-06-23

Cap Color	Additive	Sample Type	Primary Applications	Key Considerations
Red	None/Clot activator	Serum	Routine biochemistry (liver/kidney function), immunology tests (tumor markers, hepatitis/HIV), blood bank testing	Clot activator accelerates coagulation. For emergencies, use orange-red tubes.
Gold	Inert gel separator + Clot activator	Serum	Emergency biochemistry (cardiac enzymes, thyroid function), therapeutic drug monitoring	Gel barrier separates cells from serum; stable for ≤48 hours.
Green	Sodium/Lithium heparin	Plasma/Whole blood	Electrolytes, blood gas analysis, hemorheology studies	CONTRAINDICATED for WBC count (heparin causes cell clumping).
Light Green	Lithium heparin + Inert gel	Plasma	Emergency plasma tests (e.g., ICU), electrolyte analysis	Rapid plasma separation minimizes cellular contamination.
Lavender (Purple)	EDTA (K₂/K₃)	Whole blood	CBC, blood typing, HbA1c	CONTRAINDICATED for coagulation/calcium/potassium tests (EDTA chelates ions).
Light Blue	Sodium citrate (3.2%~3.8%)	Plasma	Coagulation studies (PT, APTT, fibrinogen)	Strict 1:9 blood-to-anticoagulant ratio required; underfilling alters results.
Black	Sodium citrate (3.2%)	Whole blood	Erythrocyte sedimentation rate (ESR)	Fixed 1:4 anticoagulant-to-blood ratio; excess anticoagulant dilutes samples.
Gray	Sodium fluoride + Potassium oxalate	Plasma/Whole blood	Glucose testing (inhibits glycolysis)	CONTRAINDICATED for urease-based urea assays; may interfere with enzymatic tests.
Royal Blue	Heparin/EDTA (trace-element-free)	Serum/Plasma	Trace element/toxicology testing (e.g., blood lead)	Uses ultrapure materials to avoid trace-element contamination.