What is a necessary action before beginning venipuncture?

Before beginning venipuncture, it is essential to clean the site with alcohol to maintain a sterile environment and reduce the risk of infection. Proper skin antisepsis is critical for preventing the introduction of pathogens into the bloodstream during the procedure. Alcohol swabs are commonly used because they effectively kill most microorganisms on the skin's surface. This practice is a standard protocol in venipuncture to ensure patient safety and promote successful blood collection.

The other options may have their relevance in a broader clinical context, but they are not necessary actions specifically tied to preparing for venipuncture. Measuring blood pressure and checking heart rate are important assessments that might be done during a comprehensive evaluation of the patient, but they do not directly pertain to the immediate preparation for the procedure. Reading the medical history can be valuable in understanding a patient’s condition, but it is not a preparatory action for performing venipuncture.