Order of Draw: Quick Reference Overview
The order of draw is the required sequence for filling blood collection tubes during a multi-tube venipuncture. When you draw blood into the wrong order, additives from one tube can carry over into the next tube on the needle tip, contaminating the sample and producing false lab results. The order of draw is defined by the Clinical and Laboratory Standards Institute (CLSI) in document H3-A6.
This matters on the NHA CPT exam. Order of draw questions make up roughly 15% of the test. You need to know each tube''s color, additive, mechanism of action, common tests, number of inversions, and special notes.
NHA CPT exam note: Order of draw accounts for approximately 15% of the NHA CPT examination. Know this chart cold.
Complete Order of Draw Chart
| # | Tube Color | Additive | Mechanism | Common Tests | Inversions | Notes |
|---|---|---|---|---|---|---|
| 1 | ⬛ Yellow (SPS) or Blood Culture Bottles | Sodium polyanethol sulfonate (SPS) or aerobic/anaerobic media | SPS inhibits complement, phagocytosis, and certain antibiotics to preserve bacteria viability | Blood cultures, bacteremia workup | 8–10 | Always first — prevents skin flora contamination of subsequent tubes. Aerobic bottle filled before anaerobic. |
| 2 | 🔵 Light Blue (Citrate) | Sodium citrate (3.2%) | Binds calcium to reversibly inhibit coagulation; ratio of blood to additive is critical (9:1) | PT, PTT, INR, fibrinogen, D-dimer, factor assays | 3–4 | Must be filled to the line exactly — under- or overfill invalidates coagulation results. If drawn after a discard tube, may be second. |
| 3 | ⬜ Red (No Additive) or 🟡 Gold / SST (Serum Separator Tube) | None (plain red) or clot activator + gel (SST/gold) | Blood clots naturally (plain red) or with silica clot activator; gel forms barrier between serum and cells after centrifugation | Chemistry panels, liver function, lipid panel, thyroid function, serologic tests, drug levels, blood bank (plain red only) | 0 (plain red) or 5 (SST/gold) | SST/gold tubes must NOT be used for blood bank — the gel can interfere with crossmatch results. Use plain red for blood bank. |
| 4 | 🟠 Orange or Gray-Yellow (Rapid Serum Tube, RST) | Thrombin-based clot activator | Thrombin rapidly accelerates clot formation; serum ready in 5 minutes | STAT chemistry panels requiring rapid serum | 5–6 | Not used in all facilities. Some institutions skip this tube type entirely. |
| 5 | 🟢 Green (Heparin) | Sodium heparin or lithium heparin | Heparin inactivates thrombin and other clotting factors, preventing coagulation; plasma is the specimen | Stat chemistry (plasma faster than serum), ammonia, chromosome analysis, HLA typing | 8–10 | Do not use for coagulation testing. Lithium heparin is most common. Sodium heparin used when lithium would interfere (e.g., lithium levels). |
| 6 | 🟣 Lavender / Purple (EDTA) | EDTA (ethylenediaminetetraacetic acid), K2 or K3 salt | Chelates (binds) calcium, permanently preventing coagulation; preserves cell morphology | CBC, differential, platelets, hemoglobin A1c, blood bank (type and screen), ESR, reticulocyte count | 8–10 | Most common tube in phlebotomy. EDTA must not contaminate coagulation or chemistry tubes — this is why it follows those tubes in the order. Fill to the line; underfilling causes EDTA excess and cell shrinkage. |
| 7 | 🩷 Pink (EDTA for Blood Bank) | EDTA (same additive as lavender) | Same as lavender EDTA — chelates calcium | Type and screen, crossmatch, blood bank testing | 8–10 | Pink tubes are specifically labeled for blood bank use. Some facilities require pink over lavender for transfusion-related testing. The tube color distinction is a facility policy, not a different additive. |
| 8 | ⬜ Gray (Fluoride/Oxalate) | Potassium oxalate + sodium fluoride | Oxalate binds calcium (anticoagulant); fluoride inhibits glycolysis enzymes, preserving glucose levels | Fasting glucose, glucose tolerance test (GTT), blood alcohol, lactate | 8–10 | Always last or near last. Fluoride is toxic to cells and will lyse RBCs if it contaminates other tubes. Do not use for general chemistry — fluoride inhibits some enzyme assays. |
| 9 | 🔷 Royal Blue (Trace Elements) | EDTA, sodium heparin, or no additive (varies by stopper color within the royal blue cap) | Tube and stopper materials are certified trace-element free to prevent contamination | Heavy metals (lead, mercury, zinc), trace element panels, toxicology | Varies (0 or 8) | Position in order depends on additive type. Place after EDTA tubes if EDTA-additive royal blue; follow manufacturer guidance. The key feature is the certified-clean rubber stopper, not the additive. |
Memory Aid for the Order
A common mnemonic for the standard order is: "Stop Light, Red Gives Blood Lavender Gray" — mapping to Yellow/Blood Culture, Light Blue, Red/Gold, Green, Blue (lavender/EDTA), Gray. Different instructors use different versions; what matters is that you understand the reason behind the sequence, not just the position.
The logic behind the order:
- Blood cultures first to minimize contamination risk
- Citrate (light blue) second because it is the most sensitive to additive contamination — even trace tissue thromboplastin from the initial needle stick could affect coagulation results, which is why a discard tube is sometimes used
- Serum tubes (red/gold) before plasma tubes because silica from SST would not harm EDTA results, but EDTA contaminating chemistry is a serious problem
- Heparin (green) before EDTA because heparin contamination of EDTA tubes is less problematic than the reverse
- EDTA (lavender) near the end because EDTA is a potent anticoagulant and calcium chelator that would ruin coagulation and chemistry results
- Fluoride/oxalate (gray) last because fluoride is cytotoxic and must not contaminate any other tube
Syringe Draw Order
When using a syringe instead of an evacuated tube system, blood is drawn into the syringe first and then transferred to tubes using a blood transfer device. The order of fill remains the same as the standard order of draw. When transferring from a syringe:
- Use a blood transfer device (never force blood through a needle into a tube — this causes hemolysis)
- Allow the vacuum to pull the blood from the syringe, or gently press the plunger
- Fill tubes in the same sequence: blood culture media, light blue, red/gold, green, lavender, gray
- Do not re-needle the stoppers — this introduces air bubbles and risks needlestick injury
Syringe draws are used when veins are fragile or small and cannot withstand the vacuum pressure of an evacuated tube. However, the risk of clotting in the syringe increases with longer draw times, which can compromise coagulation samples.
Capillary (Fingerstick) Order of Draw
Capillary collections follow a different order than venipuncture. This catches many students off guard on the exam.
For fingerstick and heelstick collections, the CLSI order is:
- Blood gas specimens (if collected)
- EDTA tubes (lavender/pink) — EDTA first in capillary collection to ensure adequate anticoagulant mixing before platelets begin to aggregate
- Other additive tubes (heparin, etc.)
- Serum tubes (red, SST) — last in capillary collection
This is the opposite of venipuncture for EDTA and serum. In capillary collection, platelets activate and clump rapidly at the puncture site. Collecting EDTA first captures platelets before they aggregate, giving accurate platelet counts. In venipuncture, EDTA comes late because it would contaminate other tubes if it got on the needle.
Key distinction: Venipuncture: EDTA near the end. Capillary: EDTA first. This is a classic exam trap.
Common Manufacturer Variations
Tube colors are largely standardized across manufacturers, but some differences exist:
- BD Vacutainer vs. Greiner Bio-One: Both use the same color conventions for major tubes (lavender, light blue, red, green, gray). Minor differences exist in SST gel formulations and exact shade of some caps.
- Gold vs. tiger-top (red/black marbled): Both are SST tubes with clot activator and gel. Gold is the current standard color; tiger-top (marbled red-black) is older but still found in some facilities.
- Tan-top tubes: Used for lead testing by some manufacturers. Certified lead-free stopper. Positioned similarly to royal blue.
- Yellow-top (ACD): Acid citrate dextrose — used for HLA typing, DNA banking, and paternity testing. Different from yellow SPS tubes. Both are yellow; the additive determines use. Check the label.
Your facility will have a tube guide specific to the manufacturer they use. Always verify with the lab if you are unsure.
When Order of Draw Matters Most
In a single-tube draw, order of draw is not a concern. It only becomes relevant when you are filling more than one tube.
The highest-risk situations are:
- Coagulation studies with a light blue tube: Any EDTA or heparin contamination will directly falsify PT, PTT, and INR results. This is the most common order-of-draw error with clinical consequences.
- When the light blue tube is the only tube or the first tube: If the light blue tube is the only tube ordered, use a discard tube (plain red or extra light blue) first. This purges the needle of tissue thromboplastin from the initial puncture, which can shorten PTT falsely.
- Blood cultures: Drawing blood cultures after other tubes risks contamination with skin flora from multiple needle entries or from additive backflow.
When a Discard Tube Is Needed
A discard tube (also called a waste tube) is a plain red or light blue tube drawn and discarded before the actual specimen tubes. Use a discard tube when:
- The light blue coagulation tube is the only tube or the first tube collected (not after blood cultures)
- The draw was done through a winged (butterfly) collection set — the tubing dead space fills with air before blood reaches the first tube, which would underfill a coagulation tube. A discard tube fills the dead space first.
- Your facility policy requires it for coagulation draws regardless of collection method
With straight needle evacuated tube draws, a discard tube is generally not required before light blue if blood cultures have already been collected, or if drawing only a light blue tube in a standard multi-tube order.
Practice Questions
-
A phlebotomist needs to collect a CBC (lavender), PT/INR (light blue), and basic metabolic panel (SST/gold). What is the correct order?
A) Lavender, light blue, gold
B) Gold, light blue, lavender
C) Light blue, gold, lavender
D) Light blue, lavender, goldAnswer: C. Light blue (coagulation) is drawn before serum/SST (gold), which is drawn before EDTA (lavender).
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A fingerstick is ordered for a CBC and a glucose. What is the correct capillary order of draw?
A) Gray (glucose) first, then lavender (CBC)
B) Lavender (CBC) first, then gray (glucose)
C) Same as venipuncture order
D) Order does not matter for capillary collectionsAnswer: B. In capillary collection, EDTA tubes (lavender) are collected before other additive tubes and serum tubes. This prevents platelet clumping before the EDTA sample is collected.
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A phlebotomist is collecting a light blue coagulation tube using a butterfly needle system with no other tubes ordered. What should the phlebotomist do first?
A) Fill the light blue tube directly — butterfly needles do not require a discard tube
B) Draw a discard tube first to fill the butterfly tubing dead space
C) Switch to a straight needle to avoid the discard tube
D) Draw the light blue tube lastAnswer: B. With a butterfly (winged) collection set, the tubing holds air that fills before blood reaches the tube, causing the light blue tube to underfill. A discard tube is drawn first to fill this dead space and ensure the coagulation tube fills to the correct volume.
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Which tube should NEVER be used for blood bank crossmatch testing, even though it contains EDTA?
A) Lavender-top tube
B) Pink-top tube
C) Gold SST tube
D) Plain red tubeAnswer: C. The gold SST tube contains a gel separator. The gel can interfere with antibody detection in crossmatch testing. Blood bank requires either a plain red or a pink EDTA tube depending on facility policy. The SST/gold tube is never acceptable for blood bank.