Blood Test Bottle Colours Explained | Complete Phlebotomy Guide 2025

Drawing blood is a routine part of medical testing, but knowing which bottle colour is used for each blood test is crucial. From clot activators to anticoagulants and separation gels, each collection tube is designed for a specific test. Its stopper colour indicates the additive inside and the specific type of test it’s used for. 

Understanding these differences ensures accurate laboratory testing and smooth communication between clinical staff and the lab. Although modern systems now label blood bottles automatically, every healthcare professional should still know what each blood collection tube colour represents and why it matters.

What Colour Blood Bottles are Used for Which Tests in Phlebotomy?

Differentiating blood bottle colours is essential to ensure every sample is processed accurately for its intended test. Each tube’s coloured cap represents a specific additive designed for particular analyses. Below, we’ve outlined each collection bottle, its additive, and the tests associated with each colour.

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Red Top Blood Bottle

Red collection tubes are less commonly used and are mainly reserved for serological screenings. They help detect specific immunoglobulins (IgG and IgM) against various viruses, bacteria, or fungi. Red coloured bottles may be plain (no additives) or contain a clot activator. These collection tubes are used for the following tests:

• Viral Serology
• Hormone Level Screenings
• Drug testing
• Antibodies Tests
• Less commonly used for Fluoride and Cryoglobulins screening)

Green Blood Bottle

Green-top bottles are used for the heparinised blood screening. They come in two variants, light green and dark green, each distinguished by the additive they contain. Light green tubes include lithium heparin and a gel separator, while dark green tubes contain sodium heparin. These blood bottles are used for the following types of screenings:

• Insulin Resistance
• Gut Hormones
• Homocysteine
• Chromosomal Tests
• Amino Acids
• Aluminium Test

Light Blue Blood Bottle

The light blue tube is used for coagulation tests and must be filled exactly to the marked line. Underfilling can cause errors in test results. It contains sodium citrate, which binds to calcium ions needed for clotting, creating a reversible anticoagulant effect. The common uses of these blood bottles are in the following health screens:

• Activated Partial Thromboplastin Ratio (APTR)
• D-dimer
• Anti-Xa Assay
• INR
• Coagulation Tests
• Less commonly used in the screening of thrombophilia and specific clotting factors (factor VIII, IX, von Willebrand) 

Pink Blood Bottle

Pink top tubes, also known as Group and Save bottles, are primarily used for blood grouping and cross-matching procedures. The transfusion laboratories use these to help identify a patient’s blood group and allocate a compatible, group-specific blood for transfusion. Each pink top tube contains EDTA (ethylenediaminetetraacetic acid), an anticoagulant that prevents blood from clotting and preserves the sample. These bottles are used for:

• Group and Save (G & S)
• Direct Antiglobulin Test
• Specific Red Cell Antibodies Screening
• Crossmatch screenings

Gold Blood Bottle

Gold or yellow-top blood bottles are commonly used for a wide range of biochemistry tests. These are also known as Serum Separator Tubes (SST) and contain two additives, silica & separation gel. These additives help separate the serum from other blood components by forming a physical barrier after centrifugation. These blood draw tubes are used for the following tests:

• Urea and Electrolytes
• Bone and Lipid Profile
• Iron Test
• Thyroid and Liver Function Tests
• C-reactive Protein (CRP)
• Troponin and Creatine Kinase (CK)
• Tumour Marker Tests
• Endocrinology & Immunology screenings

Grey Blood Bottle

The Grey top bottle is specifically used for serum Glucose and serum Lactate testing.  It contains two additives: Sodium Fluoride, which inhibits glycolysis (the breakdown of glucose), and Potassium Oxalate, which acts as an anticoagulant to prevent clotting. 

• Fasting or Random Glucose Level Test
• Lactate Screening

Purple Blood Bottle

Purple (Lavender) top blood tubes are used for haematological investigations that require whole blood for analysis. These collection tubes contain EDTA, an anticoagulant that works by binding to calcium and other metal ions (lead, iron, mercury) in the blood. These collection tubes are used for the following tests:

• CBC (Complete Blood Count)
• Parathyroid Hormone
• Reticulocytes
• ESR (Erythrocyte sedimentation rate
• Red Cell Folate
• HbA1C for Diabetes
• Less commonly used for PCR tests, gut hormone screening, G6PD, and ACTH levels.

Blood Culture Collection Bottles

Blood Culture Collection Bottles contain a specialised culture medium to promote bacterial growth. These bottles vary by type - blue for aerobic, purple for anaerobic, and black for mycobacterial cultures. However, nowadays, there is a shift towards using bottles with purple-coloured tops as a standard receptacle for all blood cultures. 

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Other Blood Bottle Colours and Their Uses

Several less common blood collection bottles are occasionally used in clinical settings. These are:

• White: Used for comprehensive molecular diagnostics, such as PCR or DNA Amplification studies. 
• Black: Used for paediatric ESR.
• Orange: Used for Stat Serum testing using a thrombin-based clot activator.
• Light Yellow: Used for tissue typing, DNA analysis, and HLA phenotyping. 
• Tan: Used for Lead (Pb) testing.

Blood Collection Tubes Reference Guide

What Should be the Order of Draw for Multiple Tube Collections?

When collecting multiple specimens, the order of draw is important to prevent cross-contamination between additives and ensure accurate test results. The standard recommended order is:

1. Blood Culture Bottles: Aerobic to Anaerobic
2. Light Blue Top: Coagulation Tests (3.2% Sodium Citrate)
3. Serum Tubes: Red, Gold, or Yellow (SST)
4. Green Top: Heparin Tube for Plasma Chemistry Tests
5. Lavender or Purple Top: EDTA Tube for Haematology
6. Grey Top: Fluoride/oxalate Tube for Glucose and Lactate

If used, special tubes (like dark blue for trace elements or white for molecular testing) should follow the manufacturer’s instructions.

Conclusion

Understanding the correct blood collection procedure, whether through home testing or professional phlebotomy, is essential for accurate and reliable results. Knowing which tubes to use and how samples are processed ensures effective health monitoring. Book your blood test today at one of our trusted clinics across the UK, including London, Birmingham, & Manchester, and get expert care and reliable results.