What Color Tubes Are Used for Which Tests in Phlebotomy?
One of the first concepts phlebotomy students learn is that different blood collection tubes are designed for different laboratory tests. Understanding what color tubes are used for which tests in phlebotomy is essential because selecting the wrong tube can lead to specimen rejection, inaccurate test results, delayed patient care, and the need for repeat collections.
While tube colors may vary slightly among manufacturers, the additive contained within the tube determines how the specimen will be processed and what testing can be performed.
This guide explains common blood collection tube colors, their additives, and the laboratory tests they are most frequently used for.
Why Do Blood Collection Tubes Have Different Colors?
Each blood collection tube is designed for a specific purpose.
Different tubes contain different additives that may:
- Prevent clotting
- Promote clotting
- Preserve cells
- Stabilize glucose
- Separate serum or plasma
Because laboratory testing requirements vary, selecting the correct tube is critical to obtaining accurate results.
For this reason, phlebotomists must understand both tube colors and the additives they contain.
Light Blue Tube
Additive
- Sodium Citrate
Common Tests
Light blue tubes are primarily used for coagulation testing, including:
- Prothrombin Time (PT)
- International Normalized Ratio (INR)
- Activated Partial Thromboplastin Time (aPTT)
- Coagulation factor studies
Important Considerations
- Because coagulation testing depends on a specific blood-to-additive ratio, light blue tubes must be filled appropriately to ensure accurate results.
Red Tube
Additive
Depending on the manufacturer, red tubes may contain:
- No additive
- Clot activator
Common Tests
Red tubes are frequently used for:
- Chemistry testing
- Serology
- Drug levels
- Specialized laboratory testing
Important Considerations
- Blood collected in a red-top tube is typically allowed to clot before processing.
Gold or Tiger Top Tube
Additive
- Clot activator
- Serum separator gel (SST)
Common Tests
Gold and tiger-top tubes are commonly used for:
- Comprehensive Metabolic Panels (CMP)
- Basic Metabolic Panels (BMP)
- Lipid Panels
- Liver function testing
- Thyroid testing
Important Considerations
- The separator gel forms a barrier between serum and blood cells after centrifugation.
Green Tube
Additive
- Heparin (sodium, lithium, or ammonium heparin)
Common Tests
Green-top tubes are often used for:
- Plasma chemistry testing
- Electrolyte testing
- Certain emergency department laboratory tests
Important Considerations
- Heparin prevents clot formation, allowing plasma testing to be performed.
Lavender Tube
Additive
- EDTA (Ethylenediaminetetraacetic Acid)
Common Tests
Lavender tubes are commonly used in hematology for:
- Complete Blood Count (CBC)
- Hemoglobin testing
- Hematocrit testing
- Differential counts
Important Considerations
- EDTA preserves cellular morphology, making it ideal for hematology testing.
Pink Tube
Additive
- EDTA
Common Tests
Pink-top tubes are most commonly associated with:
- Blood bank testing
- Type and Screen
- Crossmatching
- Compatibility testing
Important Considerations
- Although pink and lavender tubes both contain EDTA, they are intended for different laboratory departments and testing purposes.
Gray Tube
Additive
Typically contains:
- Sodium fluoride
- Potassium oxalate
Common Tests
Gray tubes are commonly used for:
- Glucose testing
- Glucose tolerance testing
- Lactate testing
- Alcohol testing
Important Considerations
- The additives help preserve glucose levels by slowing cellular metabolism after collection.
Yellow Tube
Additive
Depending on the tube type, yellow tubes may contain:
- SPS (Sodium Polyanethol Sulfonate)
- ACD (Acid Citrate Dextrose)
Common Tests
Yellow tubes are frequently used for:
- Blood cultures
- Specialized immunohematology testing
- Genetic studies
- HLA testing
Important Considerations
- Blood culture collection procedures often require specific aseptic techniques to minimize contamination.
Common Tube Colors and Tests Chart
|
Tube Color |
Additive |
Common Tests |
|
Light Blue |
Sodium Citrate |
PT, INR, aPTT |
|
Red |
None or Clot Activator |
Chemistry, Serology |
|
Gold/Tiger Top |
Clot Activator + Gel |
CMP, BMP, Lipid Panel |
|
Green |
Heparin |
Plasma Chemistry |
|
Lavender |
EDTA |
CBC, Hematology |
|
Pink |
EDTA |
Blood Bank Testing |
|
Gray |
Sodium Fluoride/Potassium Oxalate |
Glucose, Lactate |
|
Yellow |
SPS or ACD |
Blood Cultures, Specialized Testing |
Why Tube Selection Matters
Selecting the wrong tube can create significant problems.
Potential consequences include:
- Specimen rejection
- Delayed results
- Repeat collections
- Additive contamination
- Inaccurate laboratory testing
Even if a specimen is collected correctly, using the wrong tube may make the sample unsuitable for testing.
Tube Color Versus Additive
One common misconception among students is that tube color alone determines testing.
In reality, the additive inside the tube is what matters most.
Manufacturers occasionally use slightly different labels or color variations, but the additive and intended use remain the primary considerations.
Successful phlebotomists learn both tube colors and the additives associated with each collection tube.
Order of Draw and Tube Colors
Understanding tube colors is closely connected to understanding the order of draw.
The standard order of draw helps prevent additive carryover between tubes and protects specimen integrity.
For example:
- Blood Cultures
- Light Blue
- Serum Tubes (Red, Gold, Tiger Top)
- Green
- Lavender/Pink
- Gray
Following the proper sequence helps reduce collection errors and supports accurate laboratory results.
Tube Color Knowledge and Certification Exams
Questions about tube colors, additives, and laboratory testing are common on certification examinations offered by:
- ASCP
- NHA
- AMT
- NCCT
- NHCO
Students preparing for certification should be comfortable identifying common tube types and matching them with their appropriate laboratory applications.
Continuing Education and Professional Growth
Understanding tube selection remains important throughout a phlebotomist's career.
Continuing education topics such as:
- Specimen integrity
- Additive carryover
- Laboratory quality assurance
- Collection best practices
can help reinforce proper collection techniques and improve specimen quality.
PhlebCE offers continuing education resources designed to help phlebotomy professionals maintain and expand their knowledge of specimen collection and laboratory practices.
Understanding what color tubes are used for which tests in phlebotomy is an essential component of specimen collection. Each tube contains specific additives designed for particular laboratory applications, and selecting the correct tube helps ensure accurate results and optimal patient care.
By learning common tube colors, additives, and testing applications, phlebotomists can reduce errors, improve specimen quality, and support effective laboratory operations.
References
- Centers for Disease Control and Prevention. (n.d.). Laboratory quality resources. https://www.cdc.gov/labquality/index.html
- Clinical and Laboratory Standards Institute. (2017). Collection of diagnostic venous blood specimens (GP41). Clinical and Laboratory Standards Institute. https://clsi.org/standards/products/general-laboratory/documents/gp41/
- National Healthcare Certification Organization. (n.d.). NHCO. https://nhco.org
- PhlebCE. (n.d.). Continuing education resources for phlebotomy professionals. https://phlebce.com
- World Health Organization. (2010). WHO guidelines on drawing blood: Best practices in phlebotomy. World Health Organization. https://www.ncbi.nlm.nih.gov/books/NBK138650/