Reviewed against NHS, ACOG, and peer-reviewed clinical guidance.
Diarrhoea on your period is common and linked to prostaglandins, the chemicals behind cramps. In one survey, 28% of women had it on their period.
Diarrhoea on your period is common and is linked to prostaglandins, the chemicals that make the womb contract and cause cramps, which can also speed up the bowel. A 2014 survey of 156 healthy women in BMC Women's Health found 28% had diarrhoea during their period and 73% had at least one gut symptom around it.
This article draws on that 2014 BMC Women's Health survey, a 2015 review of gut symptoms across the cycle in Gastroenterology Report, American College of Obstetricians and Gynecologists (ACOG) guidance on painful periods and NHS guidance, current as of November 2026.
What Causes Diarrhoea During a Period?
Diarrhoea during a period is most likely caused by prostaglandins, hormone-like chemicals released from the womb lining as it sheds. ACOG explains that prostaglandins make the muscles of the womb contract, that levels are high on the first day of a period, and that they fall as bleeding continues.
The 2015 Gastroenterology Report review links worse abdominal pain, bloating and diarrhoea (diarrhea) during menses to these raised prostaglandin levels, along with heightened sensitivity in the gut. The same review describes slower gut transit in the luteal phase, the two weeks before a period, when progesterone is high. This is why some women ask why they feel constipated before a period and then loose once bleeding starts.
How Common Are Gut Symptoms Around a Period?
Gut symptoms around a period are very common: nearly three in four healthy women in the 2014 survey reported at least one. Abdominal pain was most frequent, followed by diarrhoea, and symptoms were similar in the 5 days before a period and during it.
| Symptom | 5 days before a period | During a period |
|---|---|---|
| Abdominal pain | 58% | 55% |
| Diarrhoea | 24% | 28% |
| Fatigue | 53% | 49% |
Diarrhoea was the one symptom more common during a period than before it. In a group of 10 women like those surveyed, about 7 would notice a gut symptom around their period and nearly 3 would have diarrhoea during it. The survey authors observed that "Emotional symptoms occurring in conjunction with GI symptoms are common perimenstrually," pointing to shared brain, gut and hormone pathways.
Solu is a women's wellness app that maps cycle-phase-aware guidance across movement, nutrition, sleep, and energy, built for women tracking hormonal, cycle, and premenstrual symptoms. Solu's phase tracker flagging the last days before a period gives a day or two of warning before gut symptoms usually start.
Is It Normal to Have Worse IBS Symptoms on Your Period?
Yes, it is normal for irritable bowel syndrome (IBS) symptoms to worsen around a period. The 2015 review reports that women with IBS often have more abdominal pain, bloating and diarrhoea during menses, and that both IBS and inflammatory bowel disease (IBD) show a stronger cyclical pattern than in women without these conditions.
The review also notes that the exact mechanism is still unclear, partly because earlier studies did not control for pain relief or the pill. As of 2026, the NHS lists pain when pooing among the symptoms of endometriosis, so bowel pain that tracks the cycle closely is worth mentioning to a GP. The links between endometriosis and other cyclical symptoms are covered in whether endometriosis is linked to migraines.
How Can You Ease Period Diarrhoea?
Period diarrhoea usually eases by treating the prostaglandins behind it and replacing lost fluid. ACOG notes that non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen reduce the prostaglandins the body makes and work best taken at the first sign of a period.
- Take an NSAID at the start of a period if it suits you, following the label or pharmacist advice.
- Drink regular fluids, since the NHS diarrhoea guide warns diarrhoea can cause dehydration.
- Keep up gentle movement, which can ease cramps, as covered in whether exercise reduces period pain.
In UAE heat, fluid lost through diarrhoea adds to sweat loss, so the guide to how much water women should drink when exercising is useful on training days. Solu's cycle-phase nutrition guidance adjusts food suggestions for the menstrual phase, alongside the wider plan in eating for each phase of the cycle.
When Should You See a Doctor About Diarrhoea on Your Period?
Call NHS 111 or a GP urgently for bloody diarrhoea, bleeding from the bottom, or diarrhoea lasting more than 7 days, as the NHS diarrhoea guide advises. Signs of dehydration that do not improve with rehydration drinks also need a call to 111. Go to A&E or call emergency services for a sudden, severe tummy ache.
Book a routine GP appointment if gut symptoms around every period are disrupting work or sleep, or if they come with severe period pain, pain when pooing or pain during sex, which can point to endometriosis. A GP can also check for IBS or IBD when bowel changes continue beyond the period.
Key Takeaways
- In a 2014 survey, 73% of healthy women had at least one gut symptom before or during their period.
- Diarrhoea affected 24% of women in the 5 days before a period and 28% during it.
- Prostaglandins peak on day 1 of a period, and NSAIDs reduce the amount the body makes.
- Bloody diarrhoea, or diarrhoea lasting more than 7 days, needs urgent advice from NHS 111 or a GP.
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