What color tubes should be used for blood collection?

Blood Collection Tube Colors and Their Applications

Blood collection tubes should be selected based on the specific test requirements, with light blue tubes (sodium citrate) for coagulation studies, red/gold tubes for serum, lavender/purple tubes (EDTA) for hematology, and green tubes (heparin) for chemistry tests. 1, 2

Recommended Order of Draw

Following the proper order of draw is critical to prevent additive cross-contamination between tubes:

1. Blood culture tubes (usually yellow or yellow-black tops)
2. Light blue tops (sodium citrate) - for coagulation studies
3. Red tops (no additives) or gold/tiger tops (serum separator) - for serum tests
4. Green tops (heparin) - for plasma chemistry tests
5. Lavender/purple tops (EDTA) - for hematology tests
6. Gray tops (sodium fluoride/potassium oxalate) - for glucose tests 1

Common Blood Collection Tubes and Their Applications

Light Blue Top Tubes (Sodium Citrate)

• Primary use: Coagulation studies (PT, PTT, fibrinogen)
• Mixing requirement: 3-4 gentle inversions
• Critical note: Must be filled completely to ensure proper blood-to-anticoagulant ratio 1

Red Top Tubes (No Additives)

• Primary use: Chemistry, serology, blood banking
• Processing: Allow 30-60 minutes for complete clot formation
• Note: No inversions needed 1, 2

Gold/Tiger Top Tubes (Serum Separator)

• Primary use: Chemistry, serology
• Mixing requirement: 5 gentle inversions
• Note: Contains clot activator and gel barrier 1

Lavender/Purple Top Tubes (EDTA)

• Primary use: Complete blood count (CBC), blood typing, HbA1c
• Mixing requirement: 8-10 gentle inversions immediately after collection
• Note: Preferred for RNA analysis and molecular testing 1, 2

Green Top Tubes (Heparin)

• Primary use: Chemistry panels, plasma determinations
• Mixing requirement: 8-10 gentle inversions
• Note: Available as lithium, sodium, or ammonium heparin 1, 2

Gray Top Tubes (Sodium Fluoride/Potassium Oxalate)

• Primary use: Glucose testing, alcohol levels
• Mixing requirement: 8-10 gentle inversions
• Note: Glycolytic inhibitor preserves glucose 1, 3

Critical Handling Considerations

Proper Mixing Technique

• Gently invert tubes (180-degree turns) immediately after collection
• Inadequate mixing can result in microclots or incomplete additive distribution
• Excessive shaking can cause hemolysis 1, 2

Filling Requirements

• Fill tubes until vacuum is exhausted
• Underfilled tubes can affect test results due to improper blood-to-additive ratio
• Studies show lower plasma t-tau levels when K2-EDTA tubes were only 50% filled 1

Processing Timeframes

• Process blood samples within 2 hours of collection
• If processing must be delayed, refrigerate at 4°C (not on ice) for no more than 2 hours
• For serum tubes, allow 30-60 minutes at room temperature for clot formation 1, 2

Common Pitfalls and How to Avoid Them

1. Cross-contamination: Following the proper order of draw prevents additive carryover (e.g., EDTA contamination can falsely elevate potassium and decrease calcium levels) 4

2. Hemolysis: Use appropriate needle gauge (19-21G), avoid excessive vacuum pressure, and prevent vigorous mixing 2

3. Improper tube selection: Match tube type to the specific test requirements; using incorrect tubes can invalidate results 1, 5

4. Inadequate mixing: Ensure proper inversion of tubes with additives to prevent microclots and ensure even distribution of anticoagulants 1, 2

5. Prolonged tourniquet application: Limit tourniquet use to 60 seconds or less to prevent hemoconcentration and analyte alterations 2

By selecting the appropriate blood collection tubes and following proper collection and handling procedures, you can ensure accurate test results and optimal patient care.