For women on a combined oral contraceptive pack, an estimate for mimicking a 28-day menstrual cycle would be Day 1 = the first day of the new pill pack (first active pill).
Rationale for this suggestion:
- In natural cycle tracking, Day 1 = first day of bleeding (a clear starting point).
- The closest analogue in a pill cycle is Day 1 of the new pack, because it marks the start of a predictable 28-day regimen.
- The placebo week isn’t physiologically meaningful for “cycle day” counting — it induces a withdrawal bleed, but it doesn’t reset ovarian hormone activity in the same way natural menstruation does.
Before collecting your sample, confirm with your ordering provider which day they recommend you collect your saliva sample.