Oat grass powder comes from the young leaves of the oat plant (Avena sativa), harvested before the plant develops grain. The powder provides vitamins (especially B vitamins and vitamin K), minerals like iron and calcium, and chlorophyll. People mix it into smoothies, juices, or water.
Evidence for specific health benefits beyond basic nutrition is limited. Most people tolerate it well, and you can take it at any time of day.
Oat grass contains vitamin K, which may interfere with blood-thinning medications like warfarin. Consult a healthcare provider before use if you take anticoagulants.