Dr. Tabatha Barber explains when to test estrogen levels: around cycle day 10-12 for the follicular peak and day 21 for the luteal peak. These timings assume ovulation has happened; without it, the hormonal pattern shifts entirely.
Around cycle day 10–12.
Around cycle day 21.
So it's really important to understand that estrogen increases in peaks 2 times of the month. So it is going to look different every day of the month. We try to check it either earlier in the phase around cycle day 10 or 12 to see that first peak. Then we want to look again during the luteal phase, during that second peak of day 21, somewhere in there, and see what those levels look like. But here's the kicker, you guys, that is for a healthy, normal cycle, that ovulation has happened. And so if ovulation isn't happening, that sends a totally different message to the brain.
