Premenstrual Bloating

Fluid retention and abdominal fullness in the days before a period — driven by hormonal shifts (oestrogen and progesterone effects on salt and water handling) and often accompanied by breast tenderness and digestive slowing. It is one of the most common PMS symptoms and reliably resolves within days of bleeding starting.

Evidence synthesis: Cyclical fluid retention tracks the luteal phase hormonal pattern and resolves with menstruation — the timing itself is diagnostic. Dietary salt reduction has trial support for reducing fluid retention, and aerobic exercise trials show reduced PMS symptoms overall. Magnesium (200-360 mg) has randomised trial evidence specifically reducing premenstrual fluid retention and bloating; vitamin B6 (up to 100 mg) shows modest benefit across PMS symptoms in meta-analysis, though trial quality is mixed. Calcium (1,200 mg) reduced bloating and other PMS symptoms in a large RCT. The critical distinction: bloating that is persistent rather than cyclical, progressive, or accompanied by pelvic pain or early satiety warrants evaluation — persistent bloating is a recognised ovarian cancer warning symptom that cyclical PMS bloating must not be confused with.