Ma'anar ƙamus na "gwajin jini" hanya ce ta likitanci da ake ɗaukar samfurin jinin mutum a bincikar ko akwai wasu abubuwa, kamar su hormones, proteins, ko cututtuka masu yaduwa. Ana iya amfani da gwajin jini don gano yanayin kiwon lafiya iri-iri, gami da cututtuka, anemia, ciwon sukari, da cututtukan hanta da koda. Hakanan ana iya amfani da gwajin jini don lura da ingancin wasu jiyya da kuma tantance lafiyar mutum gaba ɗaya.