Hormones that vary
Through the cycle, FSH, LH and estradiol rise and fall. For the value to be compared with the reference range, the sample is taken on the day the doctor asked for, often between day 2 and day 5.
Counting the days
Day 1 is the first day of your period. From that date, the laboratory works out the day of the sample, checks that the chosen centre is open that day and books your visit.
If you miss the day
The day before, a message reminds you of the appointment. If you can't come, the same day of the next cycle is offered.