Free · 2026 · Phlebotomy study tool Order of draw: tube colors, additives and a free drill

The order you fill blood collection tubes in, so no tube's additive spoils the next one. Here is the CLSI order with every tube color, what it holds and what it's for, the different order for skin punctures, and a drill to lock it in. No sign-up.

Practice the order of draw

Order of draw chart: tubes, additives, tests and inversions

1. 1Blood cultures

   • Blood culture bottles or yellow SPS tube: Culture broth (bottles) or sodium polyanethol sulfonate (SPS tube). Inversions: SPS tube 8-10; bottles per their maker.

   Tests: Blood cultures (aerobic and anaerobic bottles).

   Why here: Collected under sterile technique, first, so nothing from another tube or stopper can contaminate them.

2. 2Light blue (sodium citrate)

   • Light blue: 3.2% sodium citrate. Inversions: 3-4.

   Tests: PT/INR, aPTT, fibrinogen, D-dimer. Fill to the line: 9 parts blood to 1 part citrate.

   Why here: Coagulation tests are thrown off by other additives: clot activator falsely shortens PT and aPTT, and heparin falsely prolongs clotting times. Only a blood culture, a glass no-additive tube or a plastic tube without clot activator should come before it.

3. 3Serum tubes (red, gold SST, orange RST)

   • Red (glass): None: the blood clots on its own. Inversions: 0.
   • Red (plastic): Clot activator (silica). Inversions: 5.
   • Gold or red/gray "tiger" (SST): Clot activator + gel separator. Inversions: 5.
   • Orange (RST): Thrombin-based clot activator (clots in about 5 minutes). Inversions: 5-6.

   Tests: Chemistry panels, serology, drug levels (often a red tube without gel).

   Why here: With or without clot activator, with or without gel: the blood clots and the liquid spun off is serum. They go after citrate so clot activator never reaches a coagulation tube.

4. 4Heparin (green, light green PST)

   • Green: Sodium or lithium heparin. Inversions: 8-10.
   • Light green or green/gray (PST): Lithium heparin + gel separator. Inversions: 8-10.

   Tests: Plasma chemistry, STAT chemistry, ammonia (on ice). Lithium heparin can't be used for a lithium level; sodium heparin can't be used for sodium.

   Why here: Heparin is an anticoagulant, so these give plasma. It must never reach the citrate tube, where it falsely prolongs clotting times.

5. 5EDTA (lavender, pink, tan)

   • Lavender: K2EDTA. Inversions: 8-10.
   • Pink: K2EDTA (blood bank). Inversions: 8-10.
   • Tan: K2EDTA (lead testing). Inversions: 8-10.

   Tests: CBC, hemoglobin A1c, blood smears; pink for type and crossmatch; tan for lead.

   Why here: EDTA carried into a serum or heparin tube falsely raises potassium and lowers calcium (and alkaline phosphatase), so it comes after them.

6. 6Gray (sodium fluoride/potassium oxalate)

   • Gray: Sodium fluoride + potassium oxalate. Inversions: 8-10.

   Tests: Glucose (delayed testing, tolerance tests), lactate, blood alcohol.

   Why here: Oxalate and fluoride raise potassium or sodium and lower calcium in any tube drawn after them, so gray goes last. Fluoride stops cells from using up glucose.

Colors and inversions follow BD Vacutainer's US tube guide. Other makers use some different colors and counts, so check the label on your tubes. Invert gently right after filling; never shake.

Order of draw mnemonics

Why the order matters: additive carryover

The needle that pierces one tube's stopper can carry a trace of its additive into the next tube. The order of draw puts the tubes that are easiest to spoil first. What carryover does:

Capillary (skin puncture) order of draw

Skin punctures use a different order (CLSI GP42). EDTA comes first, not near the end, because platelets clump and microclots form quickly in skin-puncture blood.

1. 1Capillary blood gases (if collected). Collected before everything else.
2. 2EDTA (lavender microcontainer). First of the containers: platelets clump and microclots form quickly in skin-puncture blood.
3. 3Other additives (heparin, fluoride). Then the other anticoagulant containers.
4. 4Serum containers. Last, because the blood is meant to clot.

Wipe away the first drop, don't squeeze hard, and mix additive microcontainers right after filling.

Rules that come with the order

• The order is the same for a tube holder, a winged set and a syringe. Fill tubes from a syringe through a safety transfer device, in the order of draw.
• With a winged set, when the light blue tube is the first or only tube, draw a discard tube first (plain no-additive or another citrate) so the tubing's air doesn't underfill the citrate tube.
• Fill light blue to the line: 9 parts blood to 1 part citrate. Underfilled citrate tubes are rejected.
• Royal blue tubes go with the tubes that share their additive: the label band shows red (none), lavender (EDTA) or green (heparin).
• Other tubes: pearl/white PPT (EDTA + gel, molecular tests) goes with EDTA; yellow ACD (acid citrate dextrose) is used for HLA, paternity and DNA testing.