Progesterone Blood Test - Additional Information

The progesterone test, sometimes known as a progesterone blood test, P4 blood test or progesterone level test, measures the progesterone blood level.

Progesterone is an important steroid hormone of the class progestogens and is involved in fertility, pregnancy and menstruation. During a normal menstrual cycle, progesterone starts at low levels and then blood levels increase after ovulation. The reason for this is that progesterone helps thicken the lining of the uterus to ready it for the implantation of an embryo if one is successfully fertilized. On any given cycle, if no implantation occurs, progesterone levels decrease and the uterine lining will slough off, resulting in menstrual bleeding. Progesterone also impacts the functioning of the cervix and the uterine muscles during the menstrual cycle and pregnancy.

The progesterone levels during the menstrual cycle explain why progesterone blood testing is often performed on the 21st day of the menstrual cycle (sometimes known as day 21 progesterone testing). If an egg was produced during a particular menstrual cycle, the progesterone level on day 21 will be elevated as the body needs high progesterone blood levels to keep the uterine lining thick and ready for implantation. If, for whatever reason, no ovulation occurs during a particular cycle, progesterone levels will be low as there is no reason for the body to keep the uterine lining thick. Because of its important role in ovulation, this progesterone test is sometimes ordered with the FSH test and the LH test.

Because of the useful information it conveys, progesterone blood testing is frequently performed by fertility specialists working with women who wish to get pregnant. The progesterone lab test is typically ordered with other fertility lab tests like the blood pregnancy test and the AMH test during an initial or ongoing fertility workup for a more comprehensive picture of possible causes of infertility or vaginal bleeding.

Progesterone has other roles in the body. Progesterone helps maintain skin health, regulate temperature and manage the immune response. Blood progesterone levels are involved with female libido and they also potentially play a role in stabilizing blood sugar and insulin levels. Progesterone also works with other hormones such as estradiol and aldosterone to help maintain appropriate hormonal balance. In conjunction with estradiol, progesterone is involved with breast development and lactation and estradiol blood testing can be helpful for assessing these functions. Progesterone also causes sodium and fluids to be increasingly excreted from the body by reducing the effects of aldosterone.

To get a progesterone test near you, simply order online & get your blood drawn at your selected Quest Diagnostics lab. Once your progesterone lab results are ready, you will be able to download them. As can be seen on the sample progesterone lab report above, the progesterone hormone blood level will be reported as a number in ng / mL. The lab report will also provide reference ranges for progesterone levels for both women who are pregnant and those who are not as well as blood levels at different stages of pregnancy or the menstrual cycle.

Fasting is not typically required for a 21 day or standard progesterone test. One exception to this guideline is that fasting should be performed if one is simultaneously getting other blood tests which do require fasting.

As an important hormone in female fertility, progesterone testing has established itself as a useful lab test whether one is just establishing baseline levels or actively checking ovulation in a woman desiring a pregnancy.