Archive · 3 Oct 2025
Menstrual Cycles and Moon Phases: What the Science Says
Some people think women's periods sync with the moon.
The average cycle and the lunar cycle are similar lengths.
A recent study looked at women's cycles over many years.
The study found that in the past, before lots of artificial lights, women's cycles sometimes lined up with the moon.
Modern lights may mess this up.
Today, it's not a dependable rule.
Your body's internal clock is more important.
It's okay if your period doesn't match the moon.
The average menstrual cycle length is close to the lunar cycle length.
A recent study examined menstrual records over many decades.
Some women showed intermittent synchronization with lunar cycles in the past.
Artificial light can disrupt any potential synchronization.
Menstrual cycles are primarily regulated by internal hormonal systems.
- Who
- Women and researchers studying menstrual cycles
- What
- The relationship between menstrual cycles and moon phases
- When
- Study analyzed data over decades; synchronization may have existed in the past
- Where
- N/A
- Why
- To investigate if a woman's menstrual cycle is related to the moon
Historical Belief
Modern Scientific View
Synchronization
Historical Belief
Some believe women's periods should or do sync with the moon.
Modern Scientific View
Evidence is too inconsistent to suggest a dependable rule.
- Average Menstrual Cycle
- 28-29.5 days
- Lunar Cycle
- 29.5 days
- Study Focus
- Menstrual records over decades
- Key Finding
- Intermittent synchrony with lunar cycles observed in some women
- Modern Impact
- Artificial light may disrupt lunar synchronization