Phlebotomy Order of Draw
Blood cultures, light blue, serum, green, lavender, gray. Here is each tube’s additive and tests, why the order matters, and the different order for finger sticks. Then test yourself.
100 NHA-style questions in 100 minutes, with order of draw, additives and special handling explained for every answer.
Or try a free Routine Blood Collections drillA blood bank type and screen is commonly collected in which tube?
Venipuncture order of draw
This is the Clinical and Laboratory Standards Institute (CLSI) order, the one NHA’s exams test. Draw only the tubes on the requisition, but always in this sequence.
| # | Tube | Additive | Common tests | Why it sits here |
|---|---|---|---|---|
| 1 | Blood culture bottles (or other sterile collection) | Culture media | Blood cultures for bacteremia and sepsis | Drawn first so nothing from another tube can contaminate a sterile specimen. |
| 2 | Light blue | Sodium citrate | Coagulation tests such as PT/INR and aPTT | Must be filled to the fill line for the 9:1 blood-to-citrate ratio. Clot activator carried over from a serum tube would distort clotting results. |
| 3 | Red, gold or red-and-gray (serum tubes) | None or clot activator, with or without gel separator | Chemistry, serology and other serum tests | Serum tubes come before every anticoagulant tube so anticoagulant can’t carry into them. |
| 4 | Green or light green | Heparin (lithium or sodium), with or without gel | Plasma chemistry, often STAT chemistry | Heparin carried forward into a coagulation or serum tube would interfere with clotting. |
| 5 | Lavender, purple or pink | EDTA | Hematology such as the CBC; pink for blood bank | EDTA binds calcium and contains potassium, so carryover falsely lowers calcium and raises potassium in later tubes. That is why it comes near the end. |
| 6 | Gray | Sodium fluoride and potassium oxalate | Glucose, lactate and blood alcohol | Fluoride stops glycolysis; oxalate is an anticoagulant. Last because its additives would disturb most other tests. |
See if you can apply it under time pressure
100 NHA-style questions in 100 minutes, with order of draw, additives and special handling explained for every answer.
Or try a free Routine Blood Collections drillCapillary (finger stick and heel stick) order
Skin punctures use a different order (CLSI GP42). Wipe away the first drop of blood, then collect:
- 1Blood gases
Capillary blood gas collection, when ordered, comes first.
- 2EDTA (lavender) microtube
Platelets begin to clump at the puncture site, so the hematology sample is collected before them.
- 3Other additive microtubes
Heparin and other anticoagulant microtubes next.
- 4Serum microtubes
Serum tubes last, because the sample is meant to clot.
Mistakes that get specimens rejected
- Under-filling the light blue tube. Too little blood upsets the 9:1 ratio and the specimen is rejected.
- Drawing light blue first through a winged (butterfly) set without a discard tube. The air in the tubing short-fills the citrate tube; draw a non-additive or citrate discard tube first to clear it.
- Shaking tubes. Additive tubes are inverted gently, as many times as the manufacturer specifies, to mix without hemolysis.
- Using the venipuncture order for a finger stick. Capillary collections put EDTA first.
- Pouring blood from one tube into another. Additives and volumes are not interchangeable.
Order of draw and tube additives belong to Routine Blood Collections, the largest domain on the NHA CPT exam (28 of 100 scored questions), and to the Phlebotomy subdomain of the CCMA exam (12 of 150).
Order of draw questions
What is the order of draw for phlebotomy?
Blood cultures (sterile) first, then light blue sodium citrate, serum tubes (red, gold or tiger top), green heparin, lavender or pink EDTA, and gray sodium fluoride/potassium oxalate last. This is the CLSI order used on the NHA CPT and CCMA exams.
Why does the order of draw matter?
Each tube’s additive can be carried into the next tube on the needle. EDTA carryover, for example, falsely raises potassium and lowers calcium, and clot activator in a coagulation tube distorts clotting times. Drawing in order keeps each additive away from tests it would affect.
Is the capillary order of draw different?
Yes. For skin punctures, collect blood gases first, then the EDTA tube, then other additive tubes, and serum tubes last. EDTA goes early because platelets start to clump at the puncture site.
Where does the gold top (SST) go in the order of draw?
With the other serum tubes: after light blue and before green. A gold or red-and-gray tube contains clot activator and gel, and it is still a serum tube.
Is there a simple way to remember the order of draw?
Think of what each tube does: sterile first, then the coagulation tube, then the tubes that clot (serum), then the anticoagulant tubes: heparin, EDTA, and fluoride/oxalate last. Learning the reason for each position makes the order stick better than a mnemonic.
Ready for the phlebotomy exam?
100 NHA-style questions in 100 minutes, with order of draw, additives and special handling explained for every answer.
Or try a free Routine Blood Collections drillKeep practicing
Order of draw per CLSI GP41 (venipuncture) and GP42 (capillary collection); exam weights from NHA CPT test plan (2024 job analysis) and NHA CCMA test plan (2022 job analysis).
Original independent practice. Not affiliated with or endorsed by the National Healthcareer Association (NHA) or CLSI.