What Is the Order of Draw?
The order of draw is the specific, standardized sequence in which blood collection tubes must be filled during a venipuncture procedure. Every phlebotomist, laboratory technician, and healthcare professional who collects blood specimens must follow this sequence to ensure accurate test results and patient safety.
The order exists because of a phenomenon called additive carryover. When a needle punctures a tube's rubber stopper, a microscopic amount of the tube's additive can remain on the needle. If the next tube is filled in the wrong sequence, that trace additive transfers into the new tube and contaminates the specimen. Even amounts too small to see with the naked eye can produce clinically significant errors in laboratory results.
For example, EDTA (the anticoagulant in lavender-top tubes) is a potent calcium chelator. If even a tiny amount of EDTA carries over into a light-blue citrate tube, it will bind calcium in the specimen and produce falsely prolonged PT and PTT values. A physician reviewing those results might incorrectly diagnose a bleeding disorder or adjust anticoagulant therapy based on erroneous data. The standardized order of draw prevents this scenario entirely.
Complete Order of Draw Chart
The following chart lists every standard blood collection tube in the correct order of draw, along with cap color, additive, number of inversions required, and commonly ordered tests. This sequence follows the CLSI H3-A6 standard used by laboratories and healthcare facilities throughout the United States.
| Draw Order | Cap Color | Additive | Inversions | Common Tests |
|---|---|---|---|---|
| 1 | Blood Culture Bottles | SPS (Sodium Polyanethol Sulfonate) — in bottle kits; yellow SPS tubes used less commonly | 8–10 | Blood cultures (aerobic & anaerobic bottles are standard; yellow SPS tubes for sterility testing) |
| 2 | Light Blue | Sodium Citrate (3.2%) | 3–4 | PT, PTT, INR, fibrinogen, coagulation factors, D-dimer |
| 3 | Red | No additive (plain serum) | 0 | Serology, immunology, blood bank (some facilities), drug levels |
| 4 | Gold / SST | Clot activator + gel separator | 5 | Chemistry panels (CMP, BMP), liver function, thyroid function, lipid panel, CRP, cardiac enzymes |
| 5 | Green | Lithium heparin, sodium heparin, or ammonium heparin | 8–10 | STAT chemistry, ammonia, lactate, arterial blood gas (ABG), electrolytes |
| 6 | Lavender / Purple | K2EDTA or K3EDTA | 8–10 | CBC (complete blood count), hemoglobin A1C, ESR (sedimentation rate), reticulocyte count, blood smear/differential |
| 7 | Pink | K2EDTA | 8–10 | Blood bank / type and screen, type and crossmatch, antibody identification |
| 8 | Gray | Sodium fluoride / potassium oxalate | 8–10 | Glucose (fasting and tolerance), blood alcohol level (BAL), lactic acid |
Mnemonics to Remember the Order
"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 separator (gold), Heparin (green), EDTA (lavender), Glucose (gray).
"Yummy Burgers Really Good, Lightly Grilled"
Yellow, Blue, Red, Gold, Lavender, Gray — remember the tube color sequence directly.
Color sequence: Yellow → Blue → Red → Gold → Green → Lavender → Pink → Gray.
Test your understanding of the order of draw
Practice with exam-style questions covering the order of draw and related clinical scenarios.
Why Does Order of Draw Matter?
Following the correct order of draw is not a suggestion — it is a clinical requirement that directly impacts patient outcomes. Laboratory test results drive the majority of medical decisions, from diagnosis to treatment plans to medication dosing. When specimens are collected in the wrong order, the resulting additive carryover can produce erroneous values that mislead clinicians.
Cross-Contamination Examples
EDTA before Citrate (Lavender before Light Blue)
EDTA is a powerful calcium chelator. Even microscopic amounts carried over into a citrate tube will bind calcium ions that are essential for the coagulation cascade. This produces falsely prolonged PT and PTT values. A patient on warfarin therapy could have their dosage incorrectly adjusted, leading to a dangerous bleeding or clotting event.
Heparin before Citrate (Green before Light Blue)
Heparin contamination of a coagulation specimen will inhibit thrombin and other clotting factors, producing falsely prolonged PTT results. This can mimic heparin therapy or a clotting factor deficiency, potentially triggering unnecessary and invasive follow-up testing.
EDTA before Chemistry (Lavender before Gold/Red)
EDTA tubes contain potassium salts (K2EDTA or K3EDTA). Carryover into a chemistry tube artificially elevates potassium levels and decreases calcium levels. A physician could misinterpret this as hyperkalemia (dangerously high potassium) and initiate emergency treatment that the patient does not need.
Oxalate/Fluoride before Other Tubes (Gray before Lavender)
Oxalate is an anticoagulant that binds calcium. If gray-top additive carries over into an EDTA tube, it can affect cell morphology and produce inaccurate CBC results, including altered white blood cell differentials and platelet counts.
In every case above, the immediate consequence is a rejected specimen and a recollection — meaning the patient must be stuck again. In the worst case, the contamination goes undetected, and clinical decisions are made on bad data. The order of draw eliminates this risk when followed consistently.
CLSI Standard H3-A6 Guidelines
The Clinical and Laboratory Standards Institute (CLSI) publishes the definitive standard for venipuncture blood collection procedures. The document H3-A6: Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture is the sixth edition of this approved guideline and is the basis for the order of draw used in clinical laboratories across the United States and internationally.
Key provisions of the CLSI H3-A6 standard include:
- Blood culture bottles must always be drawn first to minimize microbial contamination from the puncture site.
- Coagulation (citrate) tubes must be drawn before any tube containing clot activator, heparin, or EDTA to prevent additive interference with coagulation testing.
- When a coagulation tube is the first or only tube needed, a discard tube should be drawn first to clear tissue thromboplastin released during the venipuncture.
- Citrate tubes must be filled to the manufacturer's indicated fill line to maintain the critical 9:1 blood-to-anticoagulant ratio. Underfilled citrate tubes produce dilution errors and must be rejected.
- Tubes must be gently inverted the specified number of times immediately after collection to ensure proper mixing of blood with the additive. Vigorous shaking causes hemolysis.
- When using a butterfly (winged infusion) set, a discard tube should be drawn before the citrate tube to account for the dead space in the tubing.
The CLSI standard is referenced by accrediting bodies such as the College of American Pathologists (CAP) and The Joint Commission (TJC). Laboratories that deviate from these guidelines risk accreditation findings, increased specimen rejection rates, and compromised patient safety.
Common Mistakes and How to Avoid Them
Even experienced phlebotomists can make order-of-draw errors, particularly during high-volume shifts, STAT draws, or collections involving unusual tube combinations. Here are the most common mistakes and practical strategies for avoiding them.
1. Drawing the Citrate Tube Without a Discard Tube When Using a Butterfly
Butterfly sets have approximately 0.5 mL of dead space in the tubing. If a citrate tube is the first tube drawn, this dead space means the tube will be underfilled by 0.5 mL, altering the 9:1 blood-to-citrate ratio. Always draw a discard tube (any tube or a plain red-top) to fill the dead space before collecting the citrate specimen.
2. Forgetting the Order Under Pressure
During STAT draws or emergencies, it is tempting to grab whatever tube is closest. Commit a mnemonic to memory — such as "Boys Can See How Every Game" — and always lay your tubes out in order before beginning the draw. Many facilities use pre-labeled tube racks or color-coded draw guides attached to the phlebotomy cart for this reason.
3. Not Inverting Tubes Immediately
Each tube must be gently inverted the specified number of times immediately after removal from the holder. Delays in mixing can cause microclots in anticoagulant tubes, which triggers specimen rejection. Vigorous shaking is equally problematic — it causes hemolysis (rupturing of red blood cells), which affects potassium, LDH, and many other analytes. Invert gently, invert promptly, and count your inversions.
4. Underfilling the Citrate Tube
The light-blue citrate tube is the only tube where fill volume critically affects results. The 9:1 ratio of blood to sodium citrate is essential for accurate coagulation testing. An underfilled tube produces a dilution error — too much citrate relative to blood — resulting in falsely prolonged PT and PTT values. If the tube does not fill to the line, it must be discarded and a new tube collected.
5. Confusing Red and Gold Tubes
Red-top tubes (plain, no additive) and gold/SST tubes (clot activator with gel separator) are both drawn in the serum position but serve different purposes. Red tops are used for serology and blood bank testing where gel contact could interfere. Gold/SSTs are used for most chemistry panels. Check the requisition carefully and use the correct tube — they are not always interchangeable.
6. Ignoring Facility-Specific Protocols
While the CLSI standard provides the universal order of draw, individual facilities may have specific variations. Some hospitals draw blood bank (pink) tubes at a different position or require a separate venipuncture for blood bank specimens. Always know and follow your facility's standard operating procedure (SOP), which takes precedence in practice.
Special Situations in Order of Draw
Syringe Draws
When blood is collected with a syringe (for example, from difficult veins or pediatric patients), the blood must be transferred to tubes using a syringe transfer device — never by removing the tube stopper and pouring. During transfer, the citrate tube should be filled first (since accurate fill volume is most critical), followed by the remaining tubes in the standard order of draw.
Capillary (Dermal Puncture) Collections
The capillary order of draw is different from venipuncture. For capillary collections, the order is: (1) EDTA tubes (lavender) first, (2) other additive tubes second, and (3) serum tubes (red) last. This prioritization ensures that hematology specimens (CBC) are collected before platelets begin to aggregate at the puncture site. Note that blood gases, when collected by capillary, are always collected first regardless of other tubes.
Blood Bank Specimens (Pink Top)
Pink-top tubes contain the same EDTA anticoagulant as lavender tubes but are dedicated to blood bank testing (type and screen, type and crossmatch). They are drawn in the EDTA position — after heparin (green) and alongside or after lavender tubes. Pink-top tubes have strict labeling requirements: patient name, medical record number, date, time, and phlebotomist initials must be applied at the bedside, often verified against a dedicated blood bank wristband. Some facilities require a separate venipuncture for blood bank specimens to minimize patient identification errors.