4 Collection Tubes and Order of Draw
Learn how collection tube additives determine specimen type and use, and how correct tube selection, draw order, handling, and contamination prevention support reliable test results.
How tubes support testing
Collection tubes contain additives or other features that preserve blood in a form suitable for particular tests. An additive may prevent clotting, promote clotting, separate cells from serum or plasma, or preserve an analyte. Choosing the correct tube, collecting the required volume, and following the correct order help produce reliable results.
The required may be serum, plasma, or whole blood; these are not interchangeable. Use the tube specified for the test, and check both the tube label and the receiving laboratory’s test directory because colors and additives are not universal across manufacturers or laboratories.
Common tubes and their uses
Common tube colors can help identify a tube, but the label and laboratory instructions determine its additive and intended use.
Blood culture bottles: Contain culture medium and often an anticoagulant. They are used for blood microbiology and require the laboratory’s sterile blood-culture procedure.
Light blue: Contains and collects citrated plasma for coagulation tests.
Red: Contains no additive or a clot activator, depending on the tube. It is used for serum testing, such as chemistry or serology, as specified by the laboratory.
Gold or red/gray (tiger top): Contains a clot activator and serum-separator gel; commonly used to collect serum for chemistry and serology.
Green: Usually contains lithium or sodium heparin and collects heparinized plasma for selected chemistry tests. The type of heparin matters for some tests.
Light green: Contains lithium heparin and separator gel; used as a plasma-separator tube for selected chemistry tests.
Lavender or purple: Contains , commonly K₂EDTA or K₃EDTA, and collects whole blood for hematology tests such as a CBC.
Pink: Contains and commonly collects whole blood for blood-bank testing. Confirm the laboratory’s requirements.
Gray: Commonly contains sodium fluoride with potassium oxalate, although formulations vary. It is used for whole blood or plasma tests such as glucose, as specified by the laboratory.
Other colors: Royal blue, tan, and yellow ACD tubes are among those used for specialized tests, such as trace elements, lead, or cell/tissue studies. Identify these by the label and test instructions, not by color alone.
Collection and handling
Use the correct tube size and collect enough blood for the test and the required additive ratio. Fill citrate tubes to the indicated line: underfilling changes the blood-to-citrate ratio and can invalidate coagulation results. When using a winged collection set for a citrate , follow local instructions on whether a discard tube is needed to fill the tubing before collecting the citrate tube.
Gently invert additive tubes the number of times specified by the manufacturer or laboratory. Do not shake them, because vigorous mixing can damage blood cells. Allow serum tubes to clot, and process or separate specimens as directed by the laboratory.
Identify each at collection. Label tubes with the required patient identifiers and collection details according to institutional policy, and verify that the label and requisition match. Do not transfer blood between additive tubes or top up one tube from another; transfer can carry additives into the wrong and alter results.
Draw order and contamination prevention
For multiple venous specimens in one draw, the usual is:
Blood cultures or other sterile specimens.
tubes, usually light blue.
Serum tubes, such as red, gold, or tiger top.
Heparin tubes, such as green or light green.
tubes, such as lavender or pink.
Glycolytic inhibitor tubes, usually gray.
This sequence reduces the chance that an additive carried over from one tube will contaminate a later . For example, carryover can affect tests that depend on potassium or calcium measurements. Place special-purpose tubes according to their additive and the laboratory’s directions.
follows a different sequence because small-volume specimens can clot quickly. A common order is blood gases first, then , then other additive tubes, and serum tubes last. Follow device and laboratory instructions because not every test is suitable for . Avoid excessive squeezing of the puncture site, which can dilute the with tissue fluid and increase the risk of hemolysis.
Preventing contamination
Use the correct collection method and aseptic technique for the requested . Skin preparation and sterile handling are especially important for blood cultures, which are collected before other tubes.
For routine tubes, follow the applicable , fill tubes to their required volumes, and gently mix additive tubes as directed. Keep specimens properly identified, avoid transferring blood between tubes, and follow laboratory-specific instructions for unusual tubes or tests.