Focus On… Order of Blood Draw: Why Tube Sequence Matters

A Small Detail That Can Make a Big Difference

Taking blood samples is a routine part of healthcare, but obtaining a sample is only one part of the process. The correct collection tube, order of draw, fill volume, mixing technique and labelling all play an important role in producing reliable laboratory results.

For student nurses learning venepuncture, newly qualified healthcare professionals and experienced staff refreshing their knowledge, remembering the different blood collection tubes can sometimes be challenging.

This week, we're looking at why the order of blood draw matters, what the different tubes are used for and how a pocket-sized reference card can provide a convenient reminder.

What Is the Order of Blood Draw?

The order of draw is the recommended sequence in which blood collection tubes should be filled when collecting multiple samples from a patient.

Different tubes contain different additives, designed to preserve blood samples or prepare them for particular laboratory investigations.

For example, some tubes contain anticoagulants to prevent clotting, while others contain substances that help separate serum from blood cells.

When multiple tubes are collected, following the appropriate sequence helps reduce the risk of additives from one tube contaminating another.

This is known as additive carryover, and it can affect laboratory results.

Why Does the Order Matter?

Blood tests help healthcare professionals investigate symptoms, monitor conditions and make treatment decisions.

However, the accuracy of laboratory results depends partly on what happens before a sample reaches the laboratory.

This is called the pre-analytical phase.

Problems during sample collection can include:

• Using the wrong collection tube

• Collecting tubes in an inappropriate sequence

• Incorrect sample volumes

• Inadequate mixing

• Haemolysis during collection

• Incorrect patient identification or sample labelling

These problems can result in inaccurate results, rejected samples or the need to repeat a blood test.

Following the correct collection procedure helps protect sample quality and reduces avoidable delays.

Understanding Common Blood Collection Tubes

Although tube colours and their exact uses can vary between manufacturers and laboratories, several types are commonly encountered in UK healthcare.

Blood Culture Bottles

Blood cultures are used to investigate possible bloodstream infections.

They are generally collected before other routine blood tubes, using the appropriate aseptic technique and local blood culture procedure.

Light Blue – Sodium Citrate

Sodium citrate tubes are commonly used for coagulation investigations, including tests such as PT and APTT.

Correct filling is particularly important because the ratio of blood to anticoagulant affects the validity of the sample.

Gold or Red – Serum Tubes

Serum tubes are used for a range of investigations, including many biochemistry and immunology tests.

Some contain a clot activator or separator gel, while others are plain tubes.

Green – Heparin

Heparin tubes are used for certain plasma-based investigations.

The precise tests requested depend on the laboratory and its collection system.

Purple or Lavender – EDTA

EDTA tubes are commonly used for haematology investigations, including full blood counts.

EDTA prevents clotting by binding calcium.

Pink – Blood Transfusion Samples

Pink EDTA tubes are often used for blood grouping and compatibility testing.

These samples have particularly strict identification and labelling requirements.

Grey – Fluoride Oxalate

Grey tubes are commonly associated with glucose and other investigations requiring specific sample preservation.

Important: These are general examples, not a universal tube-selection chart. Always follow your local pathology laboratory's current instructions, as tube colours, additives, order and test requirements can differ.

Five Things to Remember When Collecting Blood Samples

1. Check the Local Order of Draw

The appropriate sequence depends on the collection system and local laboratory requirements.

Always use the current guidance supplied by your organisation rather than relying on tube colour alone.

2. Use the Correct Tube

Different investigations require specific sample types and additives.

If you're unsure which tube is required, check the laboratory handbook or ask the appropriate member of staff before collection.

3. Pay Attention to Fill Volumes

Underfilled tubes can affect test results, particularly when a precise blood-to-additive ratio is required.

Coagulation samples collected into sodium citrate tubes are an important example.

4. Mix Samples Correctly

Some tubes require gentle inversion to mix the sample with the additive.

The number of inversions depends on the tube and manufacturer. Vigorous shaking should be avoided.

5. Label Samples at the Patient's Side

Correct patient identification and sample labelling are essential.

Always follow local procedures, including any additional requirements for blood transfusion samples.

Focus On… The Star Resources Order of Blood Draw ID Badge Card

Remembering collection sequences, tube types and associated tests can be difficult, particularly when you're learning a new clinical skill.

The Star Resources Order of Blood Draw ID Badge Card provides a compact reference designed for healthcare students and professionals.

Rather than searching through notes, you can keep useful information close at hand during training or clinical practice.

Two Versions Available

Standard Version – One Card

A convenient reference covering the order of blood draw, designed for quick consultation.

Extended Version – Two Cards

Includes the standard reference together with an additional card containing more detailed information, including:

• Tube mixing requirements

• Common test types associated with different tubes

• Additional clinical notes and reminders

The extended version is particularly useful for students developing their knowledge of blood collection procedures.

Designed for Everyday Use

The cards are manufactured from durable plastic with a protective overlay.

Each card measures approximately 54 × 86 mm, the same size as a standard bank card.

A 1.5 cm punched attachment hole allows the cards to be carried on a suitable lanyard, badge reel or holder.

Their compact format makes them a practical addition to a collection of clinical reference cards.

Who Might Find These Cards Useful?

Student Nurses

A useful revision aid when learning about venepuncture, sample collection and the different blood tubes encountered during placements.

Practising Nurses

A convenient reference for checking less frequently encountered tube types and reinforcing familiar procedures.

Phlebotomists

A portable reminder of blood collection information, particularly when working across different clinical settings.

Healthcare Students

A practical learning resource for understanding the relationship between collection tubes, laboratory investigations and sample quality.

Why Good Samples Matter

A blood test is only as useful as the quality of the sample submitted.

The correct order of draw is one important part of that process, alongside patient identification, appropriate collection technique, tube selection, mixing and transport.

For students, developing good habits early can help establish a consistent approach to blood sampling.

For experienced healthcare professionals, having access to a quick reference can provide a useful reminder when needed.

Keep the Order of Blood Draw Close at Hand

The Star Resources Order of Blood Draw ID Badge Card brings useful blood collection information together in a compact, durable format.

Choose the standard single card for a straightforward reference or the extended two-card version for additional detail.

Explore the Order of Blood Draw ID Badge Cards

These cards are educational reference aids and do not replace practical training, competency assessment, manufacturer instructions or your organisation's current blood collection policies.