Nowadays, many patients come to the clinic and ask for a sex hormone test. Some of them just know that they need to have the test but do not know when it is appropriate, while some say that the doctor ordered them on the third day of menstruation. In my personal experience, I think there are several key time points for sex hormone test, which have different meanings. First, the third day of menstruation is to check basic endocrine secretion. At this point, we are not looking at how low the E2 is to determine whether the estrogen is insufficient, which is originally low at this stage. Rather, E2 should be less than 50ng/L at this stage. If it is higher than this value, it indicates poor ovarian reserve, which often leads to early menstruation, once in 21-25 days. FSH above 10IU/L also indicates poor ovarian reserve. At this time, progesterone is definitely low. Some doctors only check the five items of basic endocrinology without checking progesterone for this reason. At this time, both LH and FSH should be in the range of 3-7 IU/L and the values should be close to each other. The endocrine test on the third day of menstruation (withdrawal bleeding) after progesterone is definitely not allowed. It takes 20 days after progesterone use to completely eliminate its effects. Therefore, we can check the hormone level 20 days after stopping progesterone (or artificial cycle). If the patient is amenorrheic without ovulation, if the progesterone is still low, the hormone level at this time is similar to the basic endocrine, and the E2 at this time is less than 50ng/L, or even less than 20ng/L before we can say that the patient has serious estrogen deficiency. Second, ovulation check. The main purpose of this test is to check E2, LH and P. The main purpose is to see if there is a pre-ovulatory LH peak and to determine if ovulation is approaching/or has occurred, and to use ultrasound follicle monitoring to diagnose the condition and guide treatment (whether HCG injection is needed to promote ovulation and when is the best time to inject). Luteal phase examination. The best time is one week before menstruation. If the basal body temperature is taken, it is usually checked when the basal body temperature rises 6-7 days. At this time, progesterone is theoretically at its highest level in the luteal phase, up to 40nmol/L or more. If the time calculation is accurate (about 7 days after the blood draw) and the progesterone level is 15nmol/L or less at this time, the diagnosis of luteal insufficiency can be considered, personally I think it is more meaningful to check at this time for those who have repeated miscarriages (progesterone level is often low during pregnancy and miscarriage). If the progesterone level is <3nmol/L at this time, it can be determined that ovulation is not occurring. In addition, if you come here specifically to check sex hormones, it is recommended that blood be drawn around 9:00-9:30 am, and that the blood be drawn at rest after sitting in front of the laboratory for 10 minutes, so that the error fluctuations are smaller. However, clinical clinics are often not able to be bound, so they check as they come and if they find any abnormality, they will review the test next time as required.