Our editorial team creates evidence-based phlebotomy study materials, practice exams, and educational resources designed to help students prepare for certification and strengthen their clinical knowledge.
This guide has been reviewed for clinical accuracy, procedural consistency, and alignment with current evidence-based phlebotomy practices and recognized laboratory standards.
The phlebotomy order of draw is the standardized sequence used when collecting multiple blood specimens during a venipuncture. Following the correct sequence helps reduce the risk of additive carryover between tubes and protects specimen quality for laboratory testing.
For phlebotomy students and certification candidates, learning the order of draw requires more than memorizing tube colors. You should understand the relationship between each tube, its additive, the specimen type, and the reason for its position in the sequence. A phlebotomy study guide can help organize these concepts, while a phlebotomy practice test provides an opportunity to reinforce them through questions on tube sequence, additives, and specimen collection procedures.
The current CLSI venous blood collection standard organizes the major tube categories in this order: blood culture, sodium citrate, serum, heparin, EDTA, and sodium fluoride/oxalate glycolytic inhibitor.
What Is the Phlebotomy Order of Draw?
The order of draw is the sequence in which different blood collection tubes are filled during a single venipuncture when multiple specimens are required.
Collection tubes can contain different additives, including anticoagulants, clot activators, gels, or glycolytic inhibitors. If blood or an additive from one tube carries over into another tube, the specimen may no longer have the intended composition. Using a standardized sequence helps reduce this risk.
The order is therefore based on specimen requirements and additive carryover prevention, not simply on tube color. For a broader overview of venipuncture and routine specimen collection procedures, see the Routine Blood Collection Guide and Venipuncture Procedure guide.
CLSI’s current guidance applies the venous order of draw to blood collected using common methods such as evacuated tubes, a syringe, or a tube holder.
Correct Venous Order of Draw
The current CLSI sequence for major venous blood collection tube categories is:
1. Blood culture
2. Sodium citrate
3. Serum
4. Heparin
5. EDTA
6. Sodium fluoride/oxalate glycolytic inhibitor
| Order | Tube or specimen category | Common tube/closure color | Important additive or feature | Common purpose |
| 1 | Blood culture | Culture bottle/tube | Culture media | Microbiology |
| 2 | Sodium citrate | Light blue | Sodium citrate | Coagulation testing |
| 3 | Serum | Red, gold, or other serum configurations | Clot activator and/or gel depending on tube | Serum testing |
| 4 | Heparin | Green or light green | Heparin, with configuration-dependent additives | Plasma testing |
| 5 | EDTA | Lavender, pink, or other EDTA configurations | EDTA | Hematology and selected blood-bank testing |
| 6 | Fluoride/oxalate glycolytic inhibitor | Gray | Glycolytic inhibitor and/or anticoagulant depending on tube | Selected chemistry testing |
Tube colors are useful visual identifiers, but they should not be treated as universal substitutes for knowing the additive. Collection systems and tube configurations can vary, so phlebotomists should follow the applicable laboratory procedure and manufacturer’s instructions.
1. Blood Culture
Blood culture specimens are collected first in the standard venous sequence. These specimens are intended for microbiological testing and require careful collection technique to minimize contamination.
Depending on the collection system, blood cultures may be collected in bottles or specialized collection tubes rather than a conventional color-coded tube. For this reason, it is more accurate to identify this position by its specimen type rather than assigning one universal tube color.
When blood cultures are required, follow the laboratory’s approved collection procedure, including any requirements for skin antisepsis and culture collection devices.
2. Sodium Citrate Tube
The sodium citrate tube is commonly identified by a light-blue closure. It contains sodium citrate and is primarily used for coagulation testing.
The amount of blood collected is important because coagulation testing depends on the appropriate relationship between blood and anticoagulant. A tube that is inadequately filled may not provide the intended blood-to-additive ratio.
Because sodium citrate is the second major category in the venous order of draw, it follows blood cultures and precedes serum tubes.
3. Serum Tubes
Serum tubes are collected after sodium citrate tubes. Depending on the collection system, serum tubes may include red or gold closures and may contain a clot activator, separator gel, or other configuration.
Serum is obtained after blood has clotted and the specimen is processed appropriately. The exact tube configuration depends on the test and collection system, so the color alone should not be used to determine the tube’s contents.
4. Heparin Tubes
Heparin tubes follow serum tubes in the standard venous order of draw.
Green and light-green tubes are commonly associated with heparin-containing collection systems. Heparin prevents clotting and allows plasma to be obtained for appropriate laboratory testing.
As with other collection tubes, the exact additive and tube configuration should be verified against the laboratory’s requirements rather than assumed solely from the closure color.
5. EDTA Tubes
EDTA tubes follow heparin tubes.
Lavender is commonly associated with EDTA tubes, while other EDTA-containing configurations may use different closure colors for specific applications. EDTA binds calcium and is commonly used for hematology specimens.
Pink EDTA tubes, for example, may be used in blood-bank applications depending on laboratory procedures.
For exam preparation, remember the position of EDTA after heparin and before fluoride/oxalate tubes.
6. Sodium Fluoride/Oxalate Glycolytic Inhibitor Tubes
Tubes containing sodium fluoride and/or an anticoagulant such as oxalate are placed after EDTA in the standard sequence.
Gray closures are commonly associated with these tubes. Depending on the specific tube, additives can inhibit glycolysis and prevent clotting.
Because tube formulations can differ, the laboratory’s validated collection requirements should determine which tube is appropriate for a particular test.
Why Is the Order of Draw Important?
The main reason for following the order of draw is to reduce the possibility of additive carryover or cross-contamination between tubes.
Different tubes are designed to produce specific specimen types. An additive intended for one test can interfere with another test if it is unintentionally transferred into a subsequent specimen.
For example, anticoagulants and other additives have specific purposes. If an additive from one collection tube enters another tube, the resulting specimen may no longer meet the requirements of the intended test.
Following a standardized sequence helps control this preanalytical risk. For more information about proper specimen handling and preparation after collection, see the Specimen Processing Guide. You can also reinforce these specimen-handling concepts with the Specimen Processing Quiz.
This is one reason order of draw should be understood as a specimen-quality procedure, not merely a memorization exercise.
Why You Should Learn Additives, Not Just Tube Colors
One of the most common study mistakes is memorizing a list of colors without understanding what is inside each tube.
A better approach is to connect three pieces of information:
Tube category → additive → specimen/testing purpose
For example:
- Light blue → sodium citrate → coagulation
- Serum tube → clot activator and/or gel depending on configuration → serum
- Green → heparin → plasma
- Lavender → EDTA → hematology
- Gray → glycolytic inhibitor/anticoagulant configuration → selected chemistry testing
This approach is more reliable because tube colors and configurations can vary among manufacturers and collection systems.
For certification exams, understanding the additive also makes it easier to reason through scenario-based questions instead of relying entirely on memorization.
Order of Draw During Venipuncture
The order of draw is one component of a larger blood collection procedure.
After appropriate patient identification, preparation, site selection, and venipuncture, the required tubes are collected in the correct sequence. For a broader review of patient identification and preparation before blood collection, see the Patient Preparation Guide. You can also reinforce these concepts with the Patient Preparation Quiz. Tubes containing additives must also be handled according to the applicable manufacturer’s and laboratory’s instructions, including appropriate filling and mixing requirements.
The order of draw should therefore be considered alongside other specimen-collection practices rather than treated as an isolated step.
Avoid duplicating the entire venipuncture procedure when studying this topic. Focus specifically on how the sequence protects the specimens being collected.
Venous vs. Capillary Order of Draw
The venous order of draw should not simply be transferred to capillary collection.
Capillary blood collection has its own standardized sequence because the specimen and collection process differ from routine venipuncture. The ASCP Board of Certification specifically identifies Order of Draw—Venous and Capillary in its current Phlebotomy Technician examination content guidance.
This distinction is important for both clinical practice and certification preparation. For a broader review of capillary and other non-routine collection procedures, see the Special Collections Guide and reinforce your knowledge with the Special Collections Quiz.
If you are studying capillary collection, use dedicated capillary-collection guidance rather than assuming that the venous sequence applies.
Common Phlebotomy Order-of-Draw Mistakes
Memorizing only the colors
Colors can help with recognition, but they should not replace knowledge of additives and specimen types. Reviewing broader collection procedures in the Safety & Compliance Guide can also help reinforce proper practices.
Using an outdated order
Phlebotomy standards can be revised. Study materials should be checked against current authoritative guidance rather than relying on an old chart found online. The Safety & Compliance Quiz can help reinforce your understanding of current collection and safety concepts.
Assuming tube colors are universal
Different manufacturers and collection systems can use different configurations. Always follow applicable laboratory and manufacturer instructions.
Confusing venous and capillary collection
The two collection methods have different standardized procedures. Do not assume that one sequence applies to both.
Ignoring tube requirements
Correct order does not eliminate the need for appropriate tube filling, handling, mixing, and specimen processing.
How to Memorize the Phlebotomy Order of Draw
A useful way to study the major venous sequence is:
Culture → Citrate → Serum → Heparin → EDTA → Fluoride/Oxalate
Then associate each category with its main additive or specimen type.
Rather than memorizing colors in isolation, repeatedly practice identifying:
- The tube category
- The additive
- The specimen type
- Its position in the sequence
- Why it belongs in that position
This method helps you apply the sequence to questions where the tube color is not the only information provided.
Phlebotomy Order of Draw for Certification Exams
Order of draw is an important specimen-collection concept for phlebotomy certification preparation. The current ASCP PBT content guideline specifically includes order of draw for both venous and capillary collection.
For exam preparation, know the standard sequence, the major additives, common tube identifiers, and the reason the sequence is followed. Completing a Routine Blood Collection Quiz can help reinforce these concepts and improve your ability to identify the correct tube and sequence in exam-style questions.
Do not study the sequence as an isolated list. Certification questions may require you to connect a collection tube with its additive, specimen type, or collection situation.
Phlebotomy Order of Draw Practice
Test yourself by covering the order and recalling it without looking:
Blood culture → Sodium citrate → Serum → Heparin → EDTA → Sodium fluoride/oxalate glycolytic inhibitor
Then practice identifying the additive and specimen associated with each category.
Certification Tips for the Phlebotomy Order of Draw
When preparing for a phlebotomy certification exam, don’t memorize the order of draw as a list of colors alone. Focus on connecting the tube category, additive, specimen type, and position in the sequence.
Use these strategies:
- Memorize the core sequence: Blood culture → sodium citrate → serum → heparin → EDTA → sodium fluoride/oxalate glycolytic inhibitor.
- Know the major tube colors: Be familiar with commonly associated colors such as light blue for sodium citrate, green for heparin, lavender for EDTA, and gray for fluoride/oxalate configurations.
- Understand additives: Know why sodium citrate, heparin, EDTA, and glycolytic inhibitors are used rather than relying only on color recognition.
- Study venous and capillary collection separately: The order of draw is not identical for every collection method. The current ASCP Phlebotomy Technician content guideline specifically includes both venous and capillary order of draw.
- Practice scenario-based questions: Test yourself on questions that require you to identify the next tube, recognize an additive, or determine which specimen should be collected first.
- Use current study materials: Verify your study charts against current authoritative guidance, particularly the current CLSI venous blood collection standard.
- Don’t ignore collection technique: Order of draw is only one part of specimen collection. Certification questions may connect it with patient identification, tube filling, specimen handling, and other preanalytical procedures.
A useful study method is to write the six major categories from memory, then add the common color, additive, and specimen type beside each one. Repeating this exercise helps you understand the sequence rather than memorizing it mechanically.
Key Takeaways
The phlebotomy order of draw is a specimen-quality procedure designed to reduce additive carryover when multiple blood specimens are collected.
For the major venous collection categories, remember:
Blood culture → Sodium citrate → Serum → Heparin → EDTA → Sodium fluoride/oxalate glycolytic inhibitor
Learn the additives and specimen types, not just tube colors. Follow current CLSI guidance and the applicable laboratory and manufacturer instructions, and remember that capillary collection has its own order of draw.
For certification preparation, combine memorization with scenario-based practice so you can recognize the correct sequence, tube, additive, and collection method.
References
- Clinical and Laboratory Standards Institute (CLSI). PRE02: Collection of Diagnostic Venous Blood Specimens, 8th Edition. CLSI; 2025.
https://clsi.org/shop/standards/pre02/ - Clinical and Laboratory Standards Institute (CLSI). GP42: Collection of Capillary Blood Specimens.
Official CLSI GP42 page - American Society for Clinical Pathology Board of Certification (ASCP BOC). Phlebotomy Technician (PBT) Examination Resources.
Official ASCP PBT page - World Health Organization (WHO). WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. World Health Organization; 2010.
https://www.who.int/publications/i/item/9789241599221 - Centers for Disease Control and Prevention (CDC). Collect Adult Blood Culture Sets.
https://www.cdc.gov/lab-quality/php/preventing-adult-blood-culture-contamination/collect.html
What is the correct order of draw in phlebotomy?
The current CLSI venous sequence is blood culture, sodium citrate, serum, heparin, EDTA, and sodium fluoride/oxalate glycolytic inhibitor.
What tube is drawn first?
When a blood culture specimen is required, it is collected first in the standard venous order of draw. The collection device may be a culture bottle or specialized culture tube depending on the system used.
Why is the light-blue tube collected before serum tubes?
The light-blue tube contains sodium citrate and is used for coagulation testing. Its position in the standardized sequence helps minimize additive carryover between collection tubes.
Where does the lavender tube fall in the order of draw?
Lavender tubes are commonly associated with EDTA. EDTA tubes are collected after heparin and before sodium fluoride/oxalate glycolytic inhibitor tubes in the standard venous sequence.
Is the capillary order of draw the same as the venous order?
No. Capillary collection has a separate standardized sequence. Phlebotomy technicians should learn the appropriate order for each collection method.
Can tube colors vary between manufacturers?
Yes. Tube closure colors are useful identifiers, but specific configurations can vary. The additive, manufacturer’s instructions, and laboratory requirements should be considered rather than relying on color alone.
What happens if the order of draw is incorrect?
An incorrect sequence can increase the risk of additive carryover or cross-contamination between specimens. This can compromise specimen integrity and potentially affect laboratory testing. The standardized order is used to reduce this preanalytical risk.
