If you have ever noticed your bowels behaving differently in the days before or during your period, you are in very good company. Period poos are one of the most common things women experience every month and one of the least talked about. Here is what research suggests is happening in your gut across your menstrual cycle, why there is nothing to be embarrassed about, and when it is worth getting checked.
Period poos are changes in bowel habit around your period. For some women that means more frequent or softer poos, for others urgency, constipation or bloating. In one study of healthy women, 73% reported at least one gut symptom before or during their period, and chemicals called prostaglandins are thought to play a part.
How common are period poos?
Very. In a Canadian study of 156 healthy women with no known gut or gynaecological conditions, 73% reported at least one gut symptom in the five days before or during their period [1]. Abdominal pain was the most common, reported by 58% before their period and 55% during it, followed by diarrhoea, reported by 24% before and 28% during [1]. Fatigue was common too, and women who reported low mood or anxiety around their period were more likely to have several gut symptoms at once [1].
For something that affects so many women, it rarely comes up in conversation, at school or even with friends. That silence can make normal changes feel worrying and worrying changes feel normal. Knowing your own pattern is the best way to tell the difference.
What is happening in your gut across your cycle?
Prostaglandins. Before and during your period, the lining of the womb releases prostaglandins, chemicals that make the muscle of the womb contract [2]. Prostaglandins play a role in menstrual cramps and can also influence the gastrointestinal tract, which may contribute to changes in bowel movements around your period [3].
Progesterone. Hormonal fluctuations across the menstrual cycle may influence gut movement and sensitivity, although the exact mechanisms are still being worked out [3]. After ovulation, progesterone rises, and in some research it has been associated with slower movement through the gut, which may explain why some women feel more bloated or constipated in the week before their period [3]. When progesterone drops just before bleeding starts, things may speed up again [3].
Sensitivity. Research suggests ovarian hormones may also influence how sensitive the gut is, and many women with irritable bowel syndrome report that their symptoms feel worse around their period [3]. Our guide to tracking IBS patterns goes into more detail, and gut health and hormones covers the bigger picture. If you have PCOS, our piece on PCOS and gut health may also help.
| Cycle phase | What hormones are doing | What some women notice |
|---|---|---|
| Period | Oestrogen and progesterone low, prostaglandins high [2] | More frequent or softer poos, urgency or cramping for some |
| After your period | Oestrogen rising | Some women find things feel more settled |
| Around ovulation | Oestrogen peaks, then progesterone starts to rise | Mild bloating for some |
| Week before your period | Progesterone higher [3] | Bloating or constipation for some |
Know where common ends. Period poos are common, but pain that stops you getting on with your life is not something you have to put up with.
See a GP if:
- your period pain is severe, has changed or has got worse [2]
- you get pain when pooing during your period, or diarrhoea, constipation or feeling sick that comes back every period, as these can be linked to conditions such as endometriosis [4]
- you have been bloated for 3 weeks or more, or bloating comes with weight loss or blood in your poo [5]
You deserve a proper conversation about these, not reassurance that it is just your period.
Making your cycle work for you
Track two things, not one. Note the first day of each period alongside any changes in your poo, bloating and cramps. Two or three cycles of notes, or our 30 day tracking challenge, can show whether your gut follows a pattern.
Plan around the predictable bits. If you tend to feel bloated or sluggish in the week before your period, that may be a good time to keep up fluids and fibre and build in gentle movement. A slow walk is low risk, and our piece on the sedentary gut explains why sitting still may not help. Some women find peppermint tea comforting too.
For many women, a temporary change in bowel habits around their period is simply part of their normal cycle. Understanding why these changes happen can take a lot of the worry out of them.
For your next two or three cycles, keep a simple diary: the first day of your period, plus anything you notice about your poo, bloating and cramps. Gutsi, a gut health tracker, records frequency and consistency every day in the background, which can help you notice your personal baseline and see when your patterns change. Set that next to your cycle diary and you have a much clearer picture of your month.
References
- Bernstein, M. T., Graff, L. A., Avery, L., Palatnick, C., Parnerowski, K., & Targownik, L. E. (2014). Gastrointestinal symptoms before and during menses in healthy women. BMC Women's Health, 14, 14. https://doi.org/10.1186/1472-6874-14-14
- NHS. Period pain. https://www.nhs.uk/conditions/period-pain/
- Mulak, A., Taché, Y., & Larauche, M. (2014). Sex hormones in the modulation of irritable bowel syndrome. World Journal of Gastroenterology, 20(10), 2433-2448. https://doi.org/10.3748/wjg.v20.i10.2433
- NHS. Endometriosis. https://www.nhs.uk/conditions/endometriosis/
- NHS. Bloating. https://www.nhs.uk/conditions/bloating/
Gutsi provides lifestyle and wellness insights only. It is not intended to diagnose, treat, cure or prevent any disease, and should not be used as a substitute for professional medical advice.
