3 Order of Draw

Purpose of the sequence

The Order of draw is the sequence for collecting blood into multiple tubes during one venipuncture. Following the common sequence helps prevent additives or microorganisms from one tube contaminating the next and producing misleading results.

Tube colors and additives can vary by manufacturer and test. Use the laboratory’s current collection instructions when they differ from the general sequence.

Common collection sequence

The common core sequence is:

1. Blood cultures — culture bottles or collection tubes; use the required sterile technique.

2. Light blue — sodium citrate; commonly used for coagulation tests.

3. Serum tubes — red (plain or clot activator), gold, or tiger-top tubes, often containing clot activator and separator gel.

4. Green — heparin, with or without separator gel; commonly used for plasma chemistry.

5. Lavender or pink — EDTA; commonly used for hematology or blood-bank testing, respectively.

6. Gray — commonly sodium fluoride with potassium oxalate; often used for glucose-related testing.

A concise way to remember the sequence is cultures → citrate → serum → heparin → EDTA → fluoride/oxalate.

Why tube order matters

Collection-tube additives have different purposes: some prevent clotting, some activate clotting, and others preserve the specimen. If a small amount transfers between tubes, it can change a test result. For example, EDTA contamination can interfere with calcium and potassium measurements, while heparin or citrate carryover can affect coagulation testing.

Blood cultures are collected first to help protect culture specimens from contamination by material in other collection tubes.

Specialty tubes

Specialty tubes, such as yellow ACD tubes or royal-blue trace-element tubes, must be placed according to their additive and the laboratory’s instructions, not color alone. Consider whether a tube’s additive could affect the next specimen if carryover occurred. Tube colors and formulations may differ.

Reducing additive carryover

Follow the recommended sequence and the laboratory’s tube-specific instructions. Do not transfer blood between collection tubes or combine specimens from different tubes.

Use a discard tube when required. With a winged collection set, air in the tubing can prevent a light-blue citrate tube from filling adequately. If citrate is the first specimen, laboratory procedures may call for a discard tube to clear the tubing; when its only purpose is clearing air, it does not need to be filled. Follow local policy.

Fill tubes to the indicated volume, especially citrate tubes, where the blood-to-additive ratio is important for coagulation testing. Gently invert additive tubes as directed by the manufacturer; do not shake them.

Applying the sequence

For a collection that includes a blood culture, a light-blue coagulation tube, a serum tube, and an EDTA tube from one venipuncture, the sequence is blood culture → light blue → serum → EDTA.

The common sequence reduces the chance that one tube’s additive will affect another specimen. Follow the laboratory’s current procedure for special tubes, discard tubes, fill volumes, and mixing.