Your bloodstream is the blood as it flows around inside your body, through veins and arteries. Doctors use it when something gets into that moving blood and is carried along — a medicine, a poison, sugar, a germ. Ordinary English uses it the same way, most often in the pattern into the bloodstream or in the bloodstream. It names the moving blood inside a living body, not a mark on a shirt and not a stream of water.

血液、血流（體內循環的血）