Through a vein, or into a vein. A vein is a tube in the body that carries blood back to the heart. Doctors use this word when medicine, water, or liquid food goes straight into the blood with a needle and a thin tube. On hospital paper you will often see the short form IV. “An intravenous drip” is the bag hanging beside the bed and the tube that feeds into the arm. It is a hospital word. In ordinary English, people often just say IV. It is not a pill, and it is not a shot in the muscle — those are different routes.

靜脈注射的。台灣口語常說「打點滴」。