二氢叶酸（英语：Dihydrofolic acid）是一个叶酸衍生物，被二氢叶酸还原酶作用后会生成四氢叶酸。因为动植物需要四氢叶酸制造嘌呤与嘧啶，故许多药物的靶点都指向二氢叶酸还原酶以阻止核酸的合成。二氢叶酸也可被叫做二氢叶酸盐，更常用的名称是维生素B₉。

医学导航：营养学

辅助、代谢、微量元素

病理、失调、症状／人名、先天

药物（A8/11/12）

医学导航：营养学

辅助、代谢、微量元素

病理、失调、症状／人名、先天

药物（A8/11/12）

Dihydrofolic acid (conjugate base dihydrofolate) (DHF) is a folic acid (vitamin B₉) derivative which is converted to tetrahydrofolic acid by dihydrofolate reductase. Since tetrahydrofolate is needed to make both purines and pyrimidines, which are building blocks of DNA and RNA, dihydrofolate reductase is targeted by various drugs to prevent nucleic acid synthesis.