A Complete Guide to Blood Collection Tubes: Colors, Additives, and Uses
This blood collection tubes guide is a practical reference for phlebotomy technicians, nurses, and laboratory staff. Tube color indicates the additive (or lack of one), which determines whether a specimen will yield plasma, serum, or whole blood and which tests are appropriate. Understanding tube additives, common uses, and proper handling helps ensure accurate results and patient safety.
General principles
- Order of draw: Follow the recommended sequence to avoid cross-contamination of additives (sterile/blood culture tubes first, then citrate, serum tubes, heparin, EDTA, glycolytic inhibitors). For the official guidance, consult CLSI recommendations on order of draw: CLSI.
- Fill volume: Some tubes require an exact blood-to-additive ratio (notably light blue citrate tubes, typically 9:1 blood to anticoagulant). Underfilling or overfilling can alter test results.
- Mixing: Gently invert tubes after collection according to the manufacturer’s directions to mix blood with additives; vigorous shaking can hemolyze samples.
Common tube colors, additives, and typical tests
- Light Blue (sodium citrate) — Anticoagulant used for coagulation studies such as PT/INR, PTT, fibrinogen, and D-dimer. Correct fill proportion is essential; improperly filled tubes can lead to inaccurate clotting times.
- Red (no additive or clot activator) — Glass red tubes contain no additives and yield serum after clotting; plastic red tubes often contain a clot activator. Used for many serology and chemistry tests when serum without gel is preferred, and for certain drug levels and therapeutic monitoring.
- Gold or Tiger Top (SST — serum separator tube) — Contain clot activator and a gel separator to produce serum that is physically separated from cells after centrifugation. Widely used for routine chemistry panels, immunology, and serology.
- Green (heparin: lithium, sodium, or ammonium) — Heparin prevents clotting and yields plasma. Common for STAT chemistry tests, some electrolyte panels, and tests requiring plasma. Note that heparin can interfere with certain assays, so consult laboratory instructions.
- Purple/Lavender (EDTA) — Ethylenediaminetetraacetic acid chelates calcium and preserves cellular morphology. Lavender tops are the standard for complete blood counts (CBC), platelet counts, and many hematology tests. Also used for some molecular assays.
- Gray (potassium oxalate/sodium fluoride) — Sodium fluoride inhibits glycolysis and preserves glucose and lactate, while potassium oxalate acts as an anticoagulant. Gray tubes are used for fasting glucose, oral glucose tolerance testing, and ethanol testing.
- Yellow (sterile — SPS or ACD) — Two common yellow types: SPS (sodium polyanethol sulfonate) sterile tubes for blood culture collection used in microbiology; and ACD (acid citrate dextrose) tubes used for HLA testing, DNA/paternity testing, and some transfusion-related studies. Blood culture collection must follow strict sterile technique; see CDC guidance on specimen collection: CDC.
Special considerations
- Blood cultures: Use sterile yellow-top blood culture bottles/tubes and collect before antibiotics when possible. Microbiology requires careful technique to minimize contamination. Refer to microbiology best practices from the CDC and clinical labs for specifics.
- Tube selection for STAT testing: Green (heparin) or plasma-based tubes may be chosen for speed, but lab policies determine acceptable tubes for analytes.
- Interfering substances: Additives can interfere with certain assays (e.g., EDTA chelates ions, fluoride affects some enzymatic tests). When in doubt, consult the laboratory’s test menu or manufacturer instructions.
- Labeling and handling: Accurate patient identification, timely transport, and correct temperature control are critical. Some assays require ice or rapid processing (e.g., ammonia); follow lab protocols closely.
Best practices for phlebotomists
- Know the lab’s preferred tubes for frequently ordered tests and follow the standardized order of draw to reduce preanalytical errors (CLSI guidance is a reliable resource).
- Understand the difference between serum and plasma and when each is required.
- Follow institutional policies and ethical obligations, including those outlined in the NAPTP Code of Ethics and Scope of Practice.
- Maintain competence through training and certification — resources such as the NAPTP Phlebotomy Technician Course and the NAPTP Phlebotomy Instructor Certification help reinforce best practices.
Where to learn more
Authoritative resources for protocols and specimen handling include CLSI, CDC, and clinical laboratory references such as the Cleveland Clinic’s laboratory test guides: Cleveland Clinic Laboratory Medicine. For guidelines on bloodborne pathogen precautions and safe collection techniques, consult the CDC or institutional infection control policies.
This blood collection tubes guide provides a compact reference to common tubes, additives, and uses, but laboratory-specific policies and manufacturer instructions take precedence. For those preparing for certification or seeking formal recognition, NAPTP offers the NAPTP National Phlebotomy Certification Exam registration and details on the NAPTP Exam. Learn more about the association and its standards on the NAPTP About page.
