Which of the following is a sign of successful venipuncture?

Successful venipuncture is indicated by blood flowing freely into the collection tube. This essential sign confirms that the needle has been correctly inserted into the lumen of the vein, allowing blood to be drawn into the tube without obstruction. The free flow of blood confirms not only the proper placement of the needle but also that the collection system is functioning appropriately, essential for obtaining the necessary sample for lab analysis.

In clinical practice, the absence of blood flow would indicate a problem with the venipuncture, such as improper needle placement or the needle being pushed through the vein. While patient comfort and minimizing pain are important aspects of the procedure, they do not directly indicate whether the venipuncture was successful in terms of sample collection. The collapse of a vein signifies that there is an issue, such as excessive vacuum or improper technique, and indicates that blood cannot be drawn effectively. Therefore, the presence of free-flowing blood into the collection tube is the definitive indicator of a successful venipuncture.