4 Common Tests by Tube
Learn how specimen type, tube additives, common tube colors, and collection sequence relate to laboratory tests, including important exceptions and verification steps.
Match the test to its specimen
Choose a collection tube according to the specimen type and additive required by the test, not just the test name. Tube-cap colors are common conventions, but colors and acceptable specimens can vary by manufacturer and laboratory. Check the performing laboratory’s current test directory and collection instructions, especially for unusual or high-impact tests.
The main specimen types differ in how blood is collected and processed:
Whole blood: Blood cells remain in the sample; this specimen is commonly used for cell counts and some blood-bank tests.
: Blood is allowed to clot and then separated from the clot. tubes may contain a clot activator and separator gel.
: Blood is collected with an anticoagulant and then separated from blood cells. The anticoagulant must be appropriate for the test.
Tube color is a useful guide to common additives and specimen types, but it does not establish that one tube is an acceptable substitute for another.
Common blood tests and tubes
The following are common patterns, not universal substitutions. Confirm specimen and tube requirements with the performing laboratory.
Lavender or purple — : Usually whole blood for a complete blood count (), with or without differential, and hemoglobin A1c (HbA1c). specimens are typically sent as whole blood in the original tube.
Pink — : Usually whole blood for many blood-bank tests, such as type and screen or crossmatch. Follow local blood-bank requirements; pink and lavender tubes are not automatically interchangeable.
Light blue — : Citrated for coagulation tests such as PT/INR and aPTT. Fill the tube to its marked level because the blood-to-additive ratio matters.
Gold or tiger-top — : for common chemistry panels such as BMP, CMP, lipid panel, and hepatic function panel, as well as many routine chemistry, hormone, and serology tests. Some tests require a plain red tube or a different specimen, so check the directory.
Red — no additive or clot activator, depending on the tube: for selected chemistry, serology, and reference-laboratory tests. A plain red tube is not always interchangeable with an SST.
Green — heparin: Heparinized for chemistry tests when the laboratory accepts , including some routine or STAT chemistry testing. The required heparin type and whether gel is acceptable can depend on the test.
Gray — commonly fluoride with oxalate: commonly used for glucose testing when glycolysis must be inhibited. The precise additive combination can vary.
Blood-culture bottles: Whole blood collected in culture medium for detecting microorganisms. Use the bottle set and collection procedure specified by the laboratory.
Apply the common panel patterns
The common panel patterns illustrate how a test’s specimen requirement determines the tube: a generally requires whole blood; a CMP commonly uses from a gold SST; and PT/INR uses citrated from a light-blue tube. A glucose test may use a gray tube, but some laboratories accept other validated specimen types.
These examples describe common practice, not automatic substitutions. Tube type, additive, specimen, and handling requirements should be confirmed for the specific test.
Tests using urine
Not every laboratory test uses a blood tube. and urine culture use urine, usually collected in a clean-catch container and transferred to the laboratory’s specified urine tubes or transport container.
Some laboratories request separate containers for and culture. Urine-tube colors and preservatives are not the same system as blood-tube colors, so follow the laboratory’s urine collection instructions.
When multiple blood tubes are collected in one venipuncture, the usual is:
Blood cultures
Light blue/citrate
tubes
Green/heparin
Lavender or pink/
Gray/fluoride–oxalate
This sequence helps limit additive carryover between specimens. Special tubes may be placed according to their additive, so follow the local procedure.
Collection and verification
Match each test to its required specimen and additive: whole blood for and HbA1c; citrate for coagulation tests; commonly for routine chemistry panels; and the laboratory-specified tube or container for glucose, cultures, urine, and specialized tests.
Fill, mix, process, and transport specimens as directed. Verify requirements in the performing laboratory’s current test directory when a test is unusual or high-impact.