Timing matters when testing reproductive hormones because levels naturally change throughout the menstrual cycle.

FSH, LH and estradiol (E2):
These are usually tested during the early follicular phase, on cycle day 2, 3 or 4. Cycle day 1 is the first day of full menstrual bleeding. These results may help evaluate baseline ovarian function, ovulation patterns and hormonal balance.

Progesterone:
Progesterone is usually checked approximately seven days after ovulation, when it is expected to be near its peak. This is often cycle day 21 for someone with a regular 28-day cycle—but day 21 is not appropriate for everyone.

For example:
• 28-day cycle: test around day 21
• 35-day cycle: test around day 28
• Irregular cycles: timing may require ovulation tracking or individualized instructions

Hormonal medications and fertility treatments can affect test results. Your results should be interpreted together with your cycle history, symptoms and other fertility assessments.

Speak with your healthcare provider to determine the most appropriate testing time for your cycle.