Chlorella is a type of algae that grows in fresh water. The whole plant is used to make nutritional supplements and medicine. Most of the chlorella that is available in the U.S. is grown in Japan or Taiwan.It is processed and made into tablets and liquid extracts.hlorella contains large amounts of vitamin K. Vitamin K is used by the body to help blood clot. Warfarin (Coumadin) is used to slow blood clotting. By helping the blood clot, chlorella might decrease the effectiveness of warfarin (Coumadin).