How long it takes for progesterone injections to take effect depends on which condition is being treated clinically with progesterone. For example, for the treatment of menopausal blood supply, after progesterone injection, the effect will be evident in about 24-48 hours and the vaginal bleeding will be significantly reduced or the vaginal bleeding will stop. If progesterone is injected to clinically induce menstruation, this condition requires 3-7 days after menopause before withdrawal bleeding, or menstruation, occurs. In the case of progesterone, which is used to calm the fetus, the vaginal bleeding will decrease or the lower abdominal pain will be relieved about 3 days after the general intramuscular injection.