Vacutainer Colour Coding: A Complete Guide for Phlebotomy and Laboratory Professionals

Vacutainer color codes are not random—they’re a vital part of accurate blood sample collection and analysis. Each tube color represents a specific additive (or lack thereof), and that determines how the blood behaves after collection, how it must be processed, and which diagnostic tests it supports.

Whether you’re a student in phlebotomy training or a working healthcare professional, understanding the purpose behind each vacutainer is critical. Let’s dive into a detailed exploration of each color-coded tube, its use case, and what to keep in mind when handling them.

Red Cap Tube – Plain or Clot Activator Tube

Additive: No additive (glass) / Clot activator (plastic)
Purpose: Used to collect serum for various biochemical tests.
Tests: Liver function test (LFT), kidney function test (KFT), and serology.
Processing: Let the blood clot, then centrifuge to separate serum.

Do not invert the glass version; gently invert the plastic one if clot activator is present.

Yellow Top Tube – SPS or ACD Tubes

Additive:
SPS: Sodium Polyanethol Sulfonate (used in microbiology for blood cultures).
ACD: Acid-Citrate-Dextrose (used in genetic/DNA and HLA testing).

Purpose: Preserves whole blood for extended testing periods.
Tests: Blood cultures (SPS), DNA typing (ACD), paternity testing.

Not used for routine blood counts or chemistry panels.

Light Blue Tube – Citrate Tube

Additive: Sodium Citrate (usually 3.2%)

Purpose: Anticoagulant; binds calcium reversibly to prevent clotting.
Tests: PT (Prothrombin Time), aPTT (Activated Partial Thromboplastin Time), D-dimer.

Must be filled completely to ensure a proper 9:1 blood-to-additive ratio for accurate results.

Green Tube – Heparin Tube

Additive: Sodium or Lithium Heparin

Purpose: Prevents clotting by inhibiting thrombin.
Tests: Blood gas analysis, electrolytes, cardiac markers, and hormone levels.

Light green tubes come with a plasma separator gel (PST).

Lavender or Purple Tube – EDTA Tube

Additive: Ethylenediaminetetraacetic acid (EDTA)

Purpose: Chelates calcium and prevents clotting.
Tests: CBC (Complete Blood Count), ESR, HbA1c, blood films, reticulocyte counts.

Gently invert 8–10 times to mix. Avoid vigorous shaking, which can cause hemolysis.

Grey Tube – Fluoride/Oxalate Tube

Additive: Sodium fluoride + potassium oxalate or EDTA

Purpose: Prevents glycolysis (breakdown of glucose).
Tests: Blood glucose, lactate, and alcohol levels.

Why it matters:
Delays glucose breakdown for up to 72 hours at room temperature—crucial for diabetes diagnosis.

Pink Tube – Blood Bank EDTA Tube

Additive: EDTA

Purpose: Same as lavender but specifically used for immunohematology.
Tests: Blood typing, cross-matching, antibody screening.

Labeling: Needs clear and complete patient identification due to critical nature of testing.

Royal Blue Tube – Trace Element Tube

Additive: Can be none, EDTA, or heparin (check label).

Purpose: Free from trace metals; used for heavy metal analysis.
Tests: Lead, zinc, copper, arsenic.

Why special?
These tubes are chemically cleaned to avoid trace contamination.

Black Tube – ESR Tube

Additive: Sodium citrate (usually in a 1:4 ratio)

Purpose: Specialized for Erythrocyte Sedimentation Rate (ESR) testing.
Tests: ESR only.

Not Interchangeable: Do not substitute with light blue as the citrate concentration differs.

Gold Top or Tiger Top (Red/Black) – SST Tube (Serum Separator Tube)

Additive: Clot activator + gel for serum separation

Purpose: After clotting, gel creates a barrier during centrifugation.
Tests: Chemistry panels, thyroid testing, hormone levels.

Also known as “Gel tubes” or “SST” tubes in the lab.

Order of Draw: Why It’s Crucial

Always follow the standard order of draw to prevent cross-contamination:

  1. Blood culture bottles or yellow SPS

  2. Light blue (citrate)

  3. Red/gold (serum tubes)

  4. Green (heparin)

  5. Lavender/pink (EDTA)

  6. Grey (fluoride)

Why follow it?
 Mixing additives between tubes can alter results significantly, especially for coagulation and glucose tests.

Vacutainer color coding is more than a visual cue—it is a safety protocol, a laboratory standard, and a critical knowledge area for every phlebotomist and medical laboratory professional.

When in doubt, read the label, check the additive, and follow the draw order.

Understanding the reasoning behind each color helps ensure patient safety, minimizes errors, and improves lab efficiency.

Want to Learn More?

Keep this guide bookmarked or download it for training reference. If you’re in the UK and looking for certified phlebotomy training, check out London Phlebotomy Training who offer real-world practice and industry-relevant curriculum.