When getting blood work done, have you ever wondered why the phlebotomist uses different colored tubes to collect your blood samples? This is because specific tests require different additives or anticoagulants to ensure accurate results. In this blog post, we will explore the order in which blood tubes are drawn and the significance of each color.

1. Red Tube: Serum Tube

The red tube, also known as the serum tube, is the first tube typically used in a blood draw. It doesn’t contain any anticoagulants, allowing the blood to clot and separate from the serum. Serum is the clear fluid that remains after the clot forms, and it is used for various tests, including cholesterol, liver enzymes, and hormones.

2. Lavender Tube: EDTA Tube

The lavender tube contains ethylenediaminetetraacetic acid (EDTA), an anticoagulant that prevents blood from clotting. This tube is commonly used for complete blood count (CBC) tests, as it preserves the blood cells and allows for accurate cell counts and morphology observation. It is also used for blood bank tests.

3. Light Blue Tube: Citrate Tube

The light blue tube contains sodium citrate, which is used as an anticoagulant. It is primarily used for coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), to evaluate blood clotting abilities and monitor anticoagulant therapy.

4. Green Tube: Heparin Tube

The green tube contains lithium or sodium heparin, which acts as an anticoagulant. It is used for tests that require plasma, such as arterial blood gas analysis, electrolyte tests, and some enzyme assays. Heparin inhibits clotting by activating antithrombin, an enzyme that neutralizes clotting factors.

5. Gray Tube: Glycolytic Inhibitor Tube

The gray tube contains a glycolytic inhibitor, typically sodium fluoride or potassium oxalate. This tube is used for tests that require plasma glucose measurement, as it prevents the breakdown of glucose by glycolysis. It is commonly used in glucose tolerance tests and for monitoring diabetes.

Conclusion

Understanding the order in which blood tubes are drawn is crucial for accurate test results. Each tube color represents a specific additive or anticoagulant necessary for various types of tests. Phlebotomists follow a standardized draw order to ensure the integrity of the samples and the reliability of the results.

Next time you have blood work done, take a moment to appreciate the complexity behind the seemingly simple process of drawing blood. If you have any questions or want to share your experiences, please leave a comment below!