Indications Need for a venous blood sample for laboratory study Contraindications Absolute contraindications None Relative contraindications Infection or hematoma at a prospective venipuncture site Injured or massively edematous extremity Thrombotic or phlebitic vein Intravenous catheter distal to a prospective venipuncture site (may affect laboratory results if IV fluids or drugs are infusing distal to the venipuncture site) Arteriovenous graft or fistula Ipsilateral mastectomy In the above situations, use another site (eg, the opposite arm) for venipuncture.