A progesterone blood test is performed to discover how much of the progesterone hormone is in a sample of blood. This female hormone is produced whenever a mature egg is released from an ovary after a process generally known as ovulation. This hormone helps you to prepare the endometrium (uterine lining) to just accept the egg if sperm fertilizes it. If the egg goes without having to be fertilized, menstrual bleeding occurs and progesterone levels drop. Why it is so important