PROBLEM TO BE SOLVED: To provide a novel antidiabetic drug, a pharmaceutical drug for a human or an animal, and a functional food product which contain a succulent stem of Cistanche tubulosa (Shrenk) R. Wight that is a parasitic plant of the family Orobanchaceae, an extracted liquid or an extracted essence extracted therefrom, or a compound isolated from the extracted essence, and have a conventionally unknown activity therefor.SOLUTION: An antidiabetic drug, a pharmaceutical drug for a human or an animal, or a functional food product contains a succulent stem of Cistanche tubulosa (Shrenk) R. Wight, an extracted liquid obtained by extracting the succulent stem of Cistanche tubulosa (Shrenk) R. Wight with water, lower aliphatic alcohol or a hydrous substance of the lower aliphatic alcohol, an extracted essence obtained by concentrating the extract liquid, or a compound isolated therefrom as an active ingredient.
