5 Tube Selection and Order-of-Draw Practice
Learn how to select blood collection tubes by specimen and additive, follow the standard venous order of draw, and protect specimen quality during collection.
Start with the test requirement
Choose a tube according to the specimen and additive required by the performing laboratory, not by cap color alone. Tube colors are common conventions, but they can vary by manufacturer, tube type, and laboratory. Before collection, check the current test directory or collection instructions for the required tube, specimen, fill volume, handling, and transport conditions.
The specimen type determines how blood is collected and processed: is obtained after blood clots and is separated from the cells; is collected with an anticoagulant and then separated from the cells; is tested without separating its cellular components.
Common tubes and their uses
These are common examples, not universal test instructions. Confirm the tube’s additive and the test’s collection requirements, especially when a tube color can refer to more than one tube type.
Blood-culture bottles or culture tubes: sterile; some culture tubes contain SPS. Used for blood cultures in microbiology.
Light blue: ; commonly used to collect citrated for coagulation tests such as PT/INR and aPTT.
Red: may contain no additive or a clot activator, depending on the tube; used for for selected chemistry, serology, or other tests.
Gold or tiger-top: clot activator and -separator gel; used for in many routine chemistry tests.
Green: commonly contains lithium or sodium heparin; used for or in selected chemistry tests.
Lavender or purple: EDTA; commonly used for in a CBC and many hematology tests.
Pink: commonly contains EDTA and is used as a blood-bank tube for testing such as type and screen when specified.
Gray: commonly contains sodium fluoride with potassium oxalate; used for preserved blood in selected glucose testing.
Yellow: may contain ACD or SPS, depending on the tube. Some special tests, including some genetic or HLA testing, use an ACD tube when specified; some blood-culture systems use SPS.
Royal blue: may be plain, contain EDTA, or contain another additive. It is used for trace-element testing, but the exact tube must be selected according to laboratory instructions.
Follow the venous
For multiple evacuated tubes collected during one venipuncture, the general is:
Blood cultures or other sterile specimens.
tubes, typically light blue.
tubes, such as red, gold, or tiger-top.
Heparin tubes, typically green.
EDTA tubes, typically lavender or pink.
Fluoride/oxalate tubes, typically gray.
A memory aid is cultures → citrate → → heparin → EDTA → glycolytic inhibitor (gray). Place special-purpose tubes not listed here according to their additive and the laboratory’s instructions.
There is a specific restriction before a citrate tube: only blood cultures, glass nonadditive tubes, or plastic tubes without clot activator may be collected before it. Follow the facility’s procedure for special collections, including any discard-tube requirements.
Protect specimen quality
Correct collection and handling help preserve specimen integrity. Follow the tube’s fill line and laboratory instructions, and use the number of gentle inversions specified by the manufacturer or facility. Do not shake tubes; vigorous mixing can damage red cells. tubes may also require gentle mixing if they contain a clot activator.
Fill volume is especially important for light-blue citrate tubes because the blood-to-additive ratio affects coagulation results. An underfilled citrate tube can produce an incorrect ratio. An unfilled or poorly mixed anticoagulant tube may contain clots.
Allow to clot as directed before centrifugation or transport; do not handle a tube as though it were an anticoagulated tube. To help prevent , let skin antiseptic dry, avoid forceful aspiration or transfer, and handle tubes gently.
Identify the patient and label specimens at the collection site according to facility policy. Confirm that the label and requisition match. Requirements for collection time, temperature, light protection, separation, and transport can vary by test. If a specimen is in the wrong tube, is mislabeled, or otherwise fails to meet requirements, consult the laboratory rather than assuming it is acceptable.
Apply the selection and collection rules
Apply the general guidance while checking the test directory in real practice; test-specific instructions may differ.
For a CBC, a lavender EDTA tube is commonly selected.
For PT/INR and aPTT, a light-blue tube is commonly used. Fill it to the required volume to maintain the correct blood-to-additive ratio.
If blood cultures and a lavender EDTA tube are collected during the same venipuncture, collect the blood cultures first, then the EDTA tube, while following the complete if other tubes are also collected.
In the sequence of gray, green, light blue, lavender, and gold, collect light blue → gold → green → lavender → gray.
A royal-blue cap alone is not enough to select a trace-element tube; confirm the required additive and specimen type.
Do not assume a visibly underfilled light-blue tube is acceptable for routine coagulation testing. The short fill may alter the citrate ratio; follow laboratory policy about rejection or recollection.
Vigorous shaking of an additive tube risks and may otherwise compromise specimen quality.