What Is the Order of Draw?
The order of draw is the standardized sequence in which blood collection tubes must be filled during venipuncture. This sequence prevents additive carryover when chemicals from one tube contaminate another and ensures the most accurate test results possible.
Laboratories rely on the consistency of this process to maintain proper sample integrity.
Why the Order of Draw Is Important
Following the correct order of draw ensures:
1. Accurate Laboratory Results
Additives in different tubes serve unique purposes—anticoagulation, preservation, clot activation, etc. Mixing them unintentionally can alter test outcomes.
2. Reduced Risk of Cross-Contamination
Incorrect sequencing can cause chemical interference, compromising sample quality.
3. Standardization Across Healthcare Settings
A universal method keeps phlebotomy practices consistent and safe for patients and professionals.
4. Improved Patient Experience
Accuracy means fewer repeat draws, less discomfort, and better satisfaction.
The Correct Order of Draw (CLSI Standard)
Here is the officially recognized sequence according to CLSI:
1. Blood Culture Bottles (Yellow/BC Sets)
Purpose: Detect infections in the bloodstream.
2. Light Blue Tube – Sodium Citrate
Used for: Coagulation studies (PT, PTT).
3. Red or Gold/SST Tube – No Additive or Serum Separator
Used for: Chemistry, serology, immunology tests.
4. Green Tube – Heparin (Lithium or Sodium)
Used for: STAT chemistries, electrolytes.
5. Lavender or Pink Tube – EDTA
Used for: CBC, blood bank tests.
6. Gray Tube – Potassium Oxalate/Sodium Fluoride
Used for: Glucose, lactate testing.