Phlebotomy Order of Draw & Technique

01CLSI Order of Draw

Draw in this sequence to prevent additive carryover between tubes: blood culture bottles (or a sterile tube) first, then light blue (sodium citrate), then serum tubes (red or gold/SST), then green (heparin), then lavender (EDTA), then gray (fluoride/oxalate).

02Tube Colors and Additives

Light blue = sodium citrate for coagulation testing (PT/INR, PTT). Lavender = EDTA, the standard tube for CBC and other hematology tests. Green = heparin, used for STAT plasma chemistry. Gray = sodium fluoride/potassium oxalate, a glycolysis inhibitor used for glucose and lactate. Red/gold (SST) = clot activator with separator gel for serum chemistry.

03Tourniquet Time and Site Selection

Release the tourniquet within 1 minute of application to avoid hemoconcentration and a higher risk of hemolysis; if more time is needed to locate a vein, release it and let the arm rest at least 2 minutes before reapplying. The median cubital vein is preferred; avoid the arm on the same side as a mastectomy (per CLSI, drawing from that side requires physician authorization), and avoid hematomas, scarring, or IV sites.

04Preventing Hemolysis

Hemolysis (ruptured red cells) is most often caused during the draw itself: too-small a needle gauge, vigorous shaking instead of gentle inversion, drawing through a hematoma, pulling the plunger back too fast, or prolonged tourniquet time. A hemolyzed sample can falsely elevate potassium, LDH, and other analytes.

05Patient Identification

Confirm identity with two identifiers — full name plus date of birth or medical record number. A room number or bed location is never an acceptable identifier, since patients can be moved.

06Response to Patient Fainting (Syncope)

If a patient faints or feels faint during the draw: stop, release the tourniquet, remove the needle and engage its safety device, discard it in the sharps container, then lower the patient's head or recline them, loosen tight clothing, apply a cool compress, and monitor vital signs. Never leave the patient unattended, and document the event.