According to WebMD, low progesterone levels are usually caused by problems with ovulation or a possible miscarriage. There are several conditions that can result in a change in progesterone levels.
Wikipedia states that progesterone is a steroid hormone involved in the female menstrual cycle, pregnancy and the embryogenesis of humans and other species. Progesterone is a part of a class of hormones called progestogens and is the main human progestogen that occurs naturally.
According to WebMD, a blood test is required to check progesterone levels. Complications are not likely to occur when the blood is drawn, although a small bruise may develop at the puncture site. However, this bruise can be reduced by applying pressure to the puncture site for several minutes after the needle is removed. In rare cases, the vein from which the blood is drawn can become inflamed in a condition known as phlebitis. This is treated by applying warm compresses daily.
WebMD also states that the results of a progesterone test are typically available in 24 hours. Normal progesterone values, or a reference range, are used as a guide to compare the progesterone test. These ranges vary depending on the lab that measures the progesterone levels. The results of the test are then evaluated by a doctor based on health factors.