Progesterone in Oil is generally used to treat absent menstrual periods. It can also be used in treating abnormal uterine bleeding caused by hormone imbalance. It may also be used for other conditions as determined by a doctor. Progesterone in Oil is a progestin hormone. It works by restoring a normal balance of progesterone. This helps to regulate the menstrual cycle and to stop abnormal uterine bleeding that occurs when the body does not make enough progesterone on its own.