“In short, yes,” suggests Dr Enayat. “Progesterone is the dominant hormone in the luteal phase; by aiding progesterone synthesis and receptors, magnesium can help sustain the luteal phase.

“Magnesium can also curb prostaglandins and inflammation that trigger menstruation. Higher magnesium levels help regulate prostaglandins and inflammatory cytokines that would otherwise signal the shedding phase. This may delay the dropping progesterone needed for menses.”

Another theory is that magnesium could indirectly affect cycle length by influencing how other nutrients work.

“Excessive intake of any supplement, including magnesium, can disrupt the balance of other nutrients, some of which are also important for menstrual health,” explains Adeem Azhar, clinical pharmacist and co-founder of Core Prescribing Solutions. “For instance, high levels of magnesium can affect the absorption and balance of calcium, vitamin D and other minerals, potentially impacting hormonal health and menstrual regularity.”

Late period? Your magnesium supplement could be to blame (and it might not be a bad thing)