When is Day 1–the first day of your period?

My Hormonology

When is Day 1–the first day of your period?



  • Confused when the first day of your period is if you have light bleeding or spotting at the start? This general rule of thumb will help you figure it out….

UPDATED OCTOBER 30, 2021 (originally published February 9, 2017)—The question, “When was the first day of your most recent period?” can crop up quite a few times in your life: At your gynecologist’s office, if you’re undergoing a medical test or procedure, when you’re family planning and when you’re getting ready to read your daily Hormone Horoscope in my Hormone Horoscope app, Female Forecaster app or my book, 28 Days: What Your Cycle Reveals About Your Moods, Health & Potential.

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 menstrual cycle.

And while you’d think that it’s easy to figure out when your Day 1 occurs–after all, it’s the first day of your period and, well, there’s blood–sometimes it can get a little tricky. That’s because menstrual bleeding isn’t always as obvious as you’d expect it to be. Sure, it can start out with a steady flow that continues for several days, making it clear that your period has definitely begun. But, other times, you could get light bleeding that pauses for a few hours before starting again. Or you can have spotting–which is when you have just a few drops of blood–then perhaps nothing for an entire day or more.

So, when is Day 1 of your menstrual cycle?

If you’re having trouble figuring out whether the light bleeding or spotting you’re experiencing means it’s your Day 1, there’s a general rule of thumb for natural cycles (meaning no hormone birth control) that can help make it clear:

If you have spotting or light bleeding one day and this bleeding occurs again the next day, the previous day was your Day 1. That’s because it means that estrogen dropped low enough the day before to trigger the shedding of your uterine lining so you have continous bleeding. It’s just taking awhile to get a heavier flow.

If you have spotting or light bleeding one day, then no bleeding at all the next day, it was likely breakthrough bleeding, which can occur in some women leading up to their period. This means it was not your Day 1. You would wait until heavier bleeding or continuous bleeding begins to count that as your Day 1.

The above rule of thumb applies to natural cycles only since hormone birth control can cause spotting and bleeding between periods.

If you have a natural cycle, you may also experience spotting or light bleeding at ovulation in the middle of your cycle. This is a result of the egg breaking away from the ovarian follicle and has nothing to do with your period.

If you have a health issue that impacts your hormones or menstrual cycle, you may experience different menstrual bleeding patterns. So, talk with your gynecologist about your specific flow.

What if you get your period at night?

If you start bleeding in the evening or overnight, it can be confusing whether to count that as your Day 1 since there are just a few hours left in that day. For the sake of simplicity, I recommend that you do count that as your Day 1. It means your estrogen reached its lowest level that day, which is a key marker to determine where you are in your menstrual cycle.

The takeaway

Once you start seeing blood toward the end of your menstrual 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 any other bleeding for two or more days after spotting, then consider those spotty days as a continuation of your current menstrual cycle.

For further clarification or to find out about other types of flow patterns, consult with your gynecologist.

👋 Copy + paste to share with a friend:

Ever have spotting or light bleeding near the time you’re supposed to get your period and wondered if that little bit of blood meant the start of a new cycle or it doesn’t officially begin until you get a heavier flow? There’s a general rule of thumb that helps you figure it out. Learn more at MyHormonology.com/when-is-the-first-day-of-your-menstrual-cycle.

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