Are the moon and the menstrual cycle connected?

Brett Buchert · March 13, 2025

It's the age old question with a complex answer. So let's get into it! 

LENGTH

With the average menstrual cycle at around 28 days (or according to a 2019 study of 600,000 users of the Natural Cycles app, 29.3 days, on average) and the lunar cycle at 29.5 days, the timing seems more than coincidental. 

RESEARCH

Yet, research studies dating back to 1937 have found inconsistent connections between the menstrual cycle and the lunar cycle. More recent studies, including one done by the Clue period tracking app in 2019 of 1.5 million users, saw no correlation between cycle phase and lunar phase. 

However, since the moon affects natural levels of light at night, and most of us spend our days and nights almost completely inside under artificial lights at all hours, I'm not really surprised by this perceived 'lack of connection' in modern population-wide research. 

Unfortunately, we don't have the data on the cycles of pre-Industrial women, or cycle research on women living without artificial light today...

So I'm not ready to draw conclusions just yet!

While we can't go back in time, we can get a glimpse of the historic menstrual-moon connection through myths and language. 

MYTHOLOGY

In mythology, many goddess across cultures and throughout history link the moon with the divine feminine, fertility, and the menstrual cycle. 

- Hecate (Greek) - A triple goddess associated with the dark moon, magic, and liminal spaces, linked to menstrual mysteries

- Artemis (Greek) / Diana (Roman) - Virgin goddess of the moon, the hunt, protector of women in childbirth

- Isis (Egypt) - Goddess of fertility, magic, and motherhood, linked to the moon and cycles of life and death

- Hathor (Egypt) Goddess of love, beauty, and fertility, associated with menstrual blood as a source of life and power.

- Coyolxauhqui (Aztec) - Mexican goddess associated with the moon and feminine cycles.

- Chang’e (Chinese mythology) – Moon goddess representing femininity, cycles, and immortality.

- Arianrhod (Welsh) moon goddess whose name means "Silver Wheel," symbolizing the cycles of life, fate, and time.

...and many others

LINGUISTICS

There's also a clue in the word "menstruation" itself which comes from the Latin menses meaning "months," which is derived from the Greek mene meaning "moon," weaving an etymological thread between the moon and the menstrual cycle. 

SPIRITUAL TRADITION

The moon is also connected to the menstrual cycle in spiritual traditions still alive today. Some modern spiritual traditions teach that syncing your cycle with the moon can enhance intuition and personal power. And some of us call our own periods our 'moon time' or ‘moon blood.’ 

Many indigenous cultures consider menstruating women to be in a heightened spiritual state, often associating them with the power of the moon. 

And in the cycle awareness world, the lunar cycle is a framework we can use for interpreting our own cycles, to understand how our energy/expression symbolically changes from menstruation (dark/new moon) to ovulation (full moon) and back. 

ORIGIN OF [WO]MAN?

And finally, in my favorite piece to the menstrual-moon puzzle, the conjunction between the moon and the menstrual cycle may have even been the catalyst for the origin of human consciousness! That might sound wild, and the theory is more than I can fully flesh out here [read 'Blood, Bread & Roses: How Menstruation Created the World' by Judy Grahn], but the general idea is that as women noticed the connection between their own cyclical bleed and the parallel cycle of the moon above them, consciousness became externalized, linked with events outside our human experiences where we could then perceive patterns and abstract concepts. This may have been the catalyst for conceptual thought, language, and time keeping! 

From all of this, it is clear to me that there absolutely is a connection between the moon and the menstrual cycle! 

Does that mean that the moon controls the menstrual cycle? Not necessarily. (But we do know that the moon affects ocean tides across millions of square miles of water on our planets, so maybe the fluids in our bodies aren't so different…)

But really, maybe it's not even about control, but simply connection. 

As the moon above us cycles and changes, so too do we cycle and change. The connection is there for sure, and it's ours to discover. 

All this said from a girl who is cycling in near perfect time with the moon this month. Coincidence?