Dicoumarol is a naturally occurring anticoagulant that functions as a functional vitamin K depleter (similar to warfarin, a drug that dicoumarol inspired). It is also used in biochemical experiments as an inhibitor of reductases.

Dicoumarol is a natural chemical substance of combined plant and fungal origin. It is a derivative of coumarin, a substance that does not itself affect coagulation, but which is transformed into active dicoumarol. Dicoumarol does affect coagulation.