Order of Draw Mnemonic
"Boys Can See How Every Game"
Blood cultures, Coagulation (citrate), Serum (red/gold), Heparin (green), EDTA (lavender/pink), Glycolytic inhibitor (gray).
"Better Call the Surgeon — He's Expecting Guests"
Blood cultures, Citrate (light blue), Serum (red/gold), Heparin (green), EDTA (lavender), Glucose (gray).
Color sequence: Yellow (cultures) → Light blue → Red/Gold → Green → Lavender/Pink → Gray.
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Why the Order Matters: Additive Carryover
When the needle punctures a tube's stopper, a trace of that tube's additive can stay on the needle and enter the next tube. Amounts too small to see can still change results. The order of draw puts each tube where the tubes before it cannot interfere with its tests, and keeps blood cultures sterile by drawing them first.
Cross-Contamination Examples
EDTA before Chemistry (Lavender before Gold/Red/Green)
K2EDTA contains potassium and binds calcium. Carryover into a chemistry tube falsely raises potassium and falsely lowers calcium. The result can look like dangerous hyperkalemia and lead to treatment the patient does not need.
EDTA before Citrate (Lavender before Light Blue)
EDTA binds the calcium the coagulation cascade needs, so carryover into a citrate tube can falsely prolong PT and aPTT. A patient on warfarin could have their dose changed on a false result.
Heparin or Clot Activator before Citrate (Green or Red/Gold before Light Blue)
Heparin in a coagulation specimen falsely prolongs the aPTT, which can mimic heparin therapy or a factor deficiency. Clot activator from a red or gold tube can do the opposite and falsely shorten PT and aPTT.
Oxalate/Fluoride before Other Tubes (Gray before Lavender)
Oxalate binds calcium and can distort blood cell morphology, so gray-top additive carried into an EDTA tube can make a smear or differential unreliable. That is why gray is drawn last.
At best, a contaminated specimen is rejected and the patient is stuck again. At worst, the error goes unnoticed and clinical decisions are made on bad data.
The Butterfly Discard Tube Rule
When you use a butterfly (winged) collection set and a light blue citrate tube is the first tube needed, draw a discard tube first. The discard tube pulls the air out of the tubing so the citrate tube fills to its line and keeps the 9:1 blood-to-citrate ratio. BD specifies a non-additive or another coagulation tube as the discard. With a straight needle, a discard tube is not needed for routine PT or aPTT. If blood cultures are drawn with a butterfly, fill the aerobic bottle first, then the anaerobic bottle, so the tubing air goes into the aerobic bottle.
Capillary (Skin Puncture) Order of Draw
Capillary collections follow CLSI GP42-Ed7, which uses a different order from venipuncture:
- Blood gases (when collected by skin puncture)
- EDTA (lavender) microtubes
- Other additive microtubes (for example heparin)
- Serum microtubes
Blood begins clotting at the puncture site, so the specimens that must not clot come first and the serum tube, which is meant to clot, comes last. EDTA leads the tubes because hematology results are the most affected by microclots. More on technique in the capillary collection guide.
CLSI PRE02-Ed8 and the "NCCLS Order of Draw"
The Clinical and Laboratory Standards Institute (CLSI) publishes the venous collection standard PRE02-Ed8: Collection of Diagnostic Venous Blood Specimens (8th edition, February 2025), which replaced the 2017 seventh edition. CLSI was called NCCLS (National Committee for Clinical Laboratory Standards) until 2005, so the "NCCLS order of draw" in older textbooks is the same organization's guidance. Key points for collection:
- Blood cultures first; citrate before any tube with clot activator, heparin or EDTA; gray last.
- Fill citrate tubes to the indicated line to keep the 9:1 blood-to-anticoagulant ratio. Underfilled tubes are rejected.
- Invert each tube gently the recommended number of times right after collection. Shaking causes hemolysis.
- Use a discard tube with a butterfly set when citrate is the first tube.
Common Mistakes and How to Avoid Them
1. Skipping the Discard Tube with a Butterfly
If the citrate tube is first, the air in the tubing takes the place of blood and the tube underfills. Draw a non-additive or coagulation discard tube first.
2. Forgetting the Order Under Pressure
During STAT draws it is tempting to grab the closest tube. Lay your tubes out in order before you start, and use a mnemonic such as "Boys Can See How Every Game."
3. Not Inverting Tubes Immediately
Delayed mixing lets microclots form in anticoagulant tubes, and the specimen is rejected. Vigorous shaking hemolyzes the sample and raises potassium and LDH. Invert gently, promptly, and count.
4. Underfilling the Citrate Tube
Too little blood leaves too much citrate, which falsely prolongs PT and aPTT. If the tube does not fill to the line, recollect it.
5. Confusing Red and Gold Tubes
Both are drawn in the serum position, but gold SSTs contain gel and some tests (certain drug levels and blood bank work at some facilities) need a red tube without gel. Check the requisition; they are not always interchangeable.
6. Ignoring Facility-Specific Protocols
Some hospitals place blood bank (pink) tubes differently or require a separate venipuncture for blood bank specimens. Your facility's standard operating procedure takes precedence in practice.
Special Situations in Order of Draw
Syringe Draws
Transfer blood from a syringe with a safety transfer device, never by removing the stopper or pushing blood through the venipuncture needle. Fill the tubes in the same order of draw as a tube-holder draw, starting with blood cultures, then citrate.
Blood Bank Specimens (Pink Top)
Pink tubes contain K2EDTA like lavender tubes and are drawn in the EDTA position. Blood bank labeling rules are strict: label at the bedside with the patient's identifiers, date, time and your initials, often against a dedicated blood bank armband. See type and screen tube requirements.