D-dimer
A D-dimer test looks for D-dimer in blood. D-dimer is a protein fragment (small piece) that's made when a blood clot dissolves in your body.
Blood clotting is an important process that prevents you from losing too much blood when you are injured. Normally, your body will dissolve the clot once your injury has healed. With a blood clotting disorder, clots can form when you don't have an obvious injury or don't dissolve when they should. These conditions can be very serious and even life-threatening. A D-dimer test can show if you have one of these conditions.