What Is Involved in a Progesterone Blood Test?

Most doctors conduct a standard medical interview prior to scheduling a progesterone blood test. This allows them to identify any factors that might result in an inaccurate reading from the test and adjust accordingly. Some experts recommend a short period of fasting before the test in order to get even more accurate results. During the progesterone blood test itself, the attending physician extracts a small sample of blood from the patient after preparatory work, and sends the sample to a laboratory for examination. Results are often relayed back to the patient within 24 hours, barring any anomalies.

In order to get the most accurate results possible, a majority of doctors inquire about the patient's medical history so as to determine whether or not a progesterone blood test is necessary or possible. An important part of the medical interview is determining the patient's menstrual schedule; the blood test is best taken on the first or heaviest day of the cycle. Doctors usually ask whether or not the patient is on certain medications that might affect test results. The standard risks to any blood test also apply, and patients prone to fainting, bruising, and hematomas are warned that all these are possible when blood is extracted from the body. After the preliminary interview, doctors will schedule the day of the progesterone blood test, as well as give their patients several guidelines to follow in preparation for the test.

In the days or weeks prior to a progesterone blood test, patients are asked to cease taking any medications that affect hormone levels. Progesterone levels should be measured as closely to the patient's natural production as possible, in order to get accurate results. Some doctors recommend that patients fast roughly 12 hours before the blood extraction. This allows blood to be as free from test result contaminants as possible.

The test itself is relatively short. Doctors usually prepare the patients by disinfecting the area from which blood will be extracted; the arm is the most common site of extraction. After rubbing the skin with alcohol or a similar disinfectant, doctors might apply pressure in the surrounding area to engorge the blood vessels, allowing for easier extraction. A sterilized syringe is then inserted into the most visible vessel, taking in a small sample of blood. The area is cleaned again afterward and can be covered with gauze to prevent possible infection.

Blood samples are sent to labs to be examined for progesterone levels. Depending on the doctor's recommendation, the blood might be tested for other hormones, such as follicle-stimulating hormone and human chorionic gonadotropin. The results of a progesterone blood test typically arrive within the day, if no other tests are ordered or no problems arise.