If you’ve noticed that your bathroom habits change during your period – maybe you’re running to the toilet more often or dealing with diarrhoea – you’re not alone. This is an incredibly common experience that affects many menstruating people.
What’s happening in your body
The main culprits behind period poops are chemicals called prostaglandins. When your period starts, your uterus releases prostaglandins to help it contract and shed its lining. Think of prostaglandins as chemical messengers that tell your uterus to squeeze and push menstrual blood out.
Here’s the catch: prostaglandins don’t just stay in your uterus. They enter your bloodstream and affect other parts of your body that have smooth muscle – including your intestines. When prostaglandins reach your colon, they cause it to contract more intensely, which speeds up the movement of stool through your digestive system. The result? More frequent bowel movements and looser stools.
Hormones, hormones, hormones!
Hormones also play a supporting role, with progesterone being the main contributor, though other hormones play a role too. After you ovulate (around the middle of your cycle), progesterone levels rise. Progesterone is known to slow down your digestive system, which is why some people feel constipated in the week or two before their period.
When your period arrives, progesterone levels drop suddenly. This abrupt change can trigger increased bowel activity, adding to the effect of the prostaglandins.
How common is this?
Very common. Research shows that about one in three people without any digestive disorders report bowel changes during menstruation. The most dramatic changes often happen right at the start of your period, when prostaglandin levels peak and progesterone levels fall.
Studies consistently find that people report looser stools and more frequent bowel movements during their period compared to other times of the month. If you experience painful periods (dysmenorrhea), you’re even more likely to notice digestive symptoms like abdominal pain, nausea and diarrhoea during menstruation. If symptoms are severe, it’s always worth checking with your GP.
What about people with IBS?
If you have irritable bowel syndrome (IBS), you may notice that your symptoms get worse during your period. This happens because the colon in people with IBS can already be more sensitive to various triggers, so the prostaglandins released during menstruation can cause an exaggerated response.
The bottom line
Period poops are a normal part of menstruation for many people. They’re caused by the same prostaglandins that give you menstrual cramps, plus the hormonal shifts that happen when your period starts. While they can be inconvenient and uncomfortable, they’re not a sign that anything is wrong with your body – it’s just your reproductive and digestive systems responding to the same chemical signals.
If your bowel symptoms during your period are severe, interfere with your daily life, or you’re concerned about them, talk to your doctor.
References
- Effects of the Menstrual Cycle on Medical Disorders. Case AM, Reid RL. Archives of Internal Medicine. 1998;158(13):1405-12. doi:10.1001/archinte.158.13.1405. [free link]
- Prostaglandin Metabolism in Relation to the Bowel Habits of Women. Arthur C, Ament ME, Song MK. Prostaglandins, Leukotrienes, and Essential Fatty Acids. 1992;46(4):257-9. doi:10.1016/0952-3278(92)90031-d. [full paper downloaded]
- Evidence for Exacerbation of Irritable Bowel Syndrome During Menses. Whitehead WE, Cheskin LJ, Heller BR, et al. Gastroenterology. 1990;98(6):1485-9. doi:10.1016/0016-5085(90)91079-l. [full paper downloaded]
- Gastrointestinal Functioning and Menstrual Cycle Phase in Emerging Young Adult Women: A Cross-Sectional Study. BMC Gastroenterology. 2023. Mendelson S, Anbukkarasu P, Cassisi JE, Zaman W. [full paper downloaded]
