Diarrhoea during your period: what to know

Chemical signals involved in menstruation can increase bowel activity, so some people pass stools more often or have looser stools during bleeding. Cramps and bowel urgency may occur together, but diarrhoea is not caused by menstruation in every case. Food poisoning, gastroenteritis and food intolerance can produce similar symptoms. Crohn's disease, coeliac disease, irritable bowel syndrome, giardiasis and hyperthyroidism may be considered when bowel symptoms occur at other times too or come with additional changes.

Sip water regularly and use an oral rehydration drink if stools are frequent. Eat small portions of foods you tolerate, and avoid alcohol, excess caffeine and known triggers until your gut settles. Note the relationship between bleeding, cramps, stool frequency, meals and medicines across several cycles. Use period products as directed and wash your hands well. Check with a pharmacist or clinician before using anti-diarrhoeal medicine, especially if you have fever, blood in stool, significant pain or could be pregnant.

Seek urgent help for severe or one-sided abdominal pain, fainting, confusion, blood or black stool, repeated vomiting, inability to drink or very little urine. Book a review if symptoms are worsening, continue after bleeding ends, repeatedly interfere with work or sleep, or occur with fever, weight loss, unusual bleeding or pain between periods. A clinician can assess both menstrual and digestive causes.

Ask whether your symptoms fit a menstrual pattern, whether your medicines could contribute, and what examination or tests would clarify the cause.