Veteran suicides, attempts and suicidal ideation (SI) remain an urgent concern for the Veterans Health Administration (VHA). Research indicates that approximately half of veteran suicides take place within 1 month of the decedent's final VHA encounter, with one quarter occurring within 1 week. This provides a temporal window of opportunity to intervene, and necessitates development of a rapid-acting treatment for veterans with SI. Uridine shares similar brain mechanisms and neural effects with ketamin and lithium, treatments commonly used to reduce suicidal ideation. This study will test the novel intervention uridine as a rapid-acting oral treatment for veterans with suicidal ideation. The purpose of this study is to investigate whether uridine can decrease suicidal ideation in veterans when taken daily for 4 weeks.