The white-coated phlebotomist stops by your bedside to draw blood. Making sure the labels on the collection vials match your hospital ID band, she applies a tourniquet above the antecubital space inside your elbow, where the veins pop up nicely. You barely feel the venipuncture needle as she expertly slides it in. Your blood fills several tubes: a lavender top for a complete blood count, a red top for chemistries like potassium levels and a blue top to measure clotting.
“These’ll go straight to the lab,” she says, and you vaguely picture a roomful of dark countertops crowded with test-tube racks and microscopes.