The question, “When was the first day of your most recent period?” can crop up quite a few times in a woman’s life: At your gynecologist’s office, if you’re undergoing a medical test or procedure, when you’re family planning or when you’re getting ready to read your daily Hormone Horoscope on this website or in one of my Hormone Horoscope apps.
Pinpointing the first day of your period is key in these instances since it indicates that it’s your Day 1–which is the considered the official start of a new monthly menstrual cycle.
And while you’d think that it’s easy to figure out that day–after all, it’s the first day of your period–sometimes it can get a little tricky. That’s because menstrual bleeding isn’t always as obvious as you’d expect it to be. Sometimes it starts out with a steady flow that continues for several days. Other times, you get slight spotting–which is when you have just a few drops of blood–then nothing for an entire day or more.
When is Day 1 of your menstrual cycle?
So, does Day 1 of your monthly cycle begin–on the day you spot or the day you have a steady flow?
The answer depends on this:
If you have spotting one day, then a steady flow the next, the previous day was your Day 1. That’s because it means that estrogen dropped low enough to trigger the shedding of your uterine lining. It just took awhile for a heavier flow to begin.
However, if you have spotting one day, then nothing else for two or more days, it was likely breakthrough bleeding, which can occur in some women leading up to their period.
By the way, spotting can also happen around ovulation in the middle of your cycle as a result of the egg breaking away from the ovarian follicle, causing slight bleeding.
Once you start seeing red down below toward the end of your cycle, mark it on your calendar. If bleeding continues and gets heavier the next day, then that spotting day was Day 1 of your new menstrual cycle.
If you don’t see anything other bleeding for two or more days after spotting, then continue counting those days as a continuation of your current menstrual cycle.