FET progesterone start

Marina.

Planned appt Friday for repeat labs and ultrasound to possibly start PIO for FET next week. Had an ultrasound today and endometrium was 8 mm. What is the goal prior to starting the progesterone? My clinic is fast tracking things before they might possibly close and I’m worried my endometrium might not be thick enough by Friday to start the PIO for FET next week. Also how many days did you do PIO before your FET? Thank you!