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Progesterone Level

Fertility testing for progesterone level

A woman’s progesterone level is often measured to determine if ovulation has occurred. The ovaries produce a very small amount of progesterone until ovulation happens. During the first half of the menstrual cycle (the follicular phase), levels are low – generally less than 3 ng/mL. Once ovulation occurs, the ovary starts producing progesterone in higher amounts, and the levels rise to above 3 ng/mL. To document ovulation, progesterone can be tested any time during the second half of the menstrual cycle (the luteal phase) as part of our complete San Antonio fertility testing workup.

Traditionally, progesterone is tested about a week after ovulation occurs. If your cycle is 28 days long, the test should be performed around day 21. If you have a 35-day cycle, this hormone level should be tested around day 28.

Interpreting a progesterone level result

Blood progesterone tests are often misinterpreted. Some physicians mistakenly believe that the result should be 10-12 ng/ml or higher to prove that a patient is ovulating or “ovulating well,” and a patient might be worried if she sees that the number is “only” 5 or 6. But don’t worry!

The truth is, progesterone levels vary from hour to hour during the luteal phase. In fact, if you get tested a few times in the same day, the result will be different each time. Previous studies show variability from 4 – 40 ng/mL in the same day.

Low levels (less than 3 ng/mL) can be seen any time before ovulation, as well as immediately after ovulation as production is ramping up. At the end of the luteal phase (when people check for a blood pregnancy test), if there isn’t a growing pregnancy, the progesterone levels naturally fall, which signals your body to start the next cycle. So, some patients may notice a low level right before their period starts, which is a normal finding.

The main takeaway message is: the progesterone level absolutely and always needs to be correlated to the day of the menstrual cycle, in order to say it if it’s normal. Our physicians provide San Antonio fertility testing to help you understand your cycle and make recommendations for you to help optimize your chances at building a family.

Click here to make an appointment with Texas Fertility Center San Antonio to learn more about your progesterone and have a full fertility evaluation.