Sun, 03 May 2026 21:28:23 +0000

This Sneaky Flu Is Behind Your Unexplained Fatigue—It’s Period Flu, Finally Exposed Feeling perpetually drained with no clear cause? You’re not imagining it. The elusive force behind unexplained fatigue in many women may be period flu—a lesser-known but real condition that combines hormonal shifts, immune changes, and fluctuating energy patterns tied to the menstrual cycle. Finally, scientists and health experts are shining a light on this sneaky phenomenon, bringing much-needed clarity to a frustrating cycle of mystery symptoms. ## What Exactly Is Period Flu? Period flu, medically referred to as cycle-related fatigue linked to hormonal fluctuations, describes the recurring feeling of extreme exhaustion that coincides with specific phases of the menstrual cycle. Unlike typical tiredness, this fatigue often intensifies just before or during menstruation but may start days earlier, syncing with rising and falling levels of estrogen, progesterone, and other key hormones.