Final answer:
A phlebotomist should use a vein on the left arm, such as the median cubital vein, for blood collection in a patient with a right-sided mastectomy to avoid complications like lymphedema.
Step-by-step explanation:
A phlebotomist should select an alternate site for venipuncture in a patient who had a right-sided mastectomy. Avoiding the side of the mastectomy is crucial because of the potential for lymphedema due to the removal or damage of lymph nodes during surgery. Since the right lymphatic duct drains lymph fluid from the upper right side of the body into the right subclavian vein, it is important to avoid using the right arm for blood draws post-mastectomy. Therefore, the technician should select a vein on the left arm for blood collection. The median cubital vein located in the antecubital region of the left arm is a common and suitable site for this procedure.