Why is it not good to make a fist when drawing blood?

Making a fist when drawing blood can constrict the veins, making them less visible and harder to access. This tension can also lead to discomfort for the patient and may cause the vein to roll or move, complicating the process. Additionally, it can hinder proper blood flow, potentially affecting the quality of the sample collected. For these reasons, it's generally advised to keep the arm relaxed during the procedure.