Water retention driven by hormones, not food: the premenstrual progesterone-estrogen shift makes the body hold sodium and water, and progesterone slows the gut - so fullness peaks before the bleed and releases as the period starts.
The on-schedule swing confirms it is hormonal. What helps: less salt that week, steady hydration, daily movement, smaller meals, less alcohol and carbonation. What to watch: bloating that stops cycling - persistent, daily, or paired with pelvic pain, early fullness, or a changing waistline over months: get checked.
What to do
Common questions
Why do I get bloated before my period?
Water, mostly - driven by hormones, not by food. In the week before the period, the progesterone-estrogen shift tells the body to retain sodium and water (the same hormone axis that swells breasts and loosens joints), and progesterone slows gut motility, so gas and constipation add a second layer of fullness. The signature that confirms it is hormonal: it rises in the days before the bleed and releases as the period starts - a weight swing of a couple of pounds that comes and goes on schedule. What genuinely helps: salt reduction in the premenstrual week (water follows salt), steady hydration (counterintuitive but retention eases when intake is consistent), moving daily (exercise moves fluid and gut contents both), smaller meals when the gut slows, and cutting alcohol and carbonated drinks that week. What to watch: bloating that no longer cycles - persistent, daily, or paired with pelvic pain, feeling full fast, or a changing waistline over months - deserves a check, since persistent (not cyclical) bloating is a different conversation. Pymander, a free AI doctor available 24/7 by text, can help you tell the two patterns apart.