Why Do I Get Diarrhea on My Period?

Day one. You’ve already made two trips to the bathroom, the cramps are rolling in, and you’re mentally rearranging your morning around where the nearest restroom is. Last month it was the opposite, a few days of nothing at all.

Why your gut joins in

The uterus and the bowel both run on smooth muscle, and the prostaglandins released around your period don’t stay in one place. Cleveland Clinic¹ says it can mean more frequent bowel movements and loose stools.

Progesterone works in the opposite direction. Cleveland Clinic¹ says it tends to promote constipation, and that this tends to arrive around ovulation or a couple of days after. The CDHF² explains that higher progesterone before your period can slow the transit of waste through the gut. So the same month can bring constipation first and diarrhea after. For more on the slow side, see constipation.

The CDHF² says symptoms peak during the menstrual phase itself, and that people with IBS are especially likely to notice, with bloating a common complaint. See IBS and dairy and bloating for the overlap.

The cramps that come with it

The Office on Women’s Health (OWH)³ calls period pain dysmenorrhea and says more than half of women who have periods get some pain around them. Our article on bad cramps covers what’s typical.

What helps

Fluids. The CDHF² says to replace what you lose, with broths, potassium-rich fruits and vegetables and oral rehydration solutions. Cleveland Clinic¹ says to stay hydrated and to go easy on coffee, which has a laxative effect.

Food. Cleveland Clinic¹ suggests plenty of fruits, vegetables and leafy greens.

An anti-inflammatory painkiller. Cleveland Clinic¹ says taking ibuprofen before your period may prevent prostaglandin release. OWH³ says over-the-counter NSAIDs such as ibuprofen, naproxen or aspirin relieve most period pain. Check with your clinician or pharmacist that an NSAID is safe for you.

Hormonal birth control. Cleveland Clinic¹ says oral contraceptives can make periods less frequent, which makes this happen less often, though it doesn’t fix the problem. That’s a conversation for your own clinician.

The play

Try this: a bowel-and-cycle log

For two or three cycles, write down the first day of your period alongside each day’s bowel habits, constipated, normal or loose, plus cramps and bloating.

The CDHF² suggests tracking bowel movements next to your cycle dates to see the pattern.

A pattern that tracks your cycle is useful to see. Loose stools all month, or trouble that doesn’t follow the calendar, is worth taking to your appointment.

When to get checked

Cleveland Clinic¹ says to see a doctor for severe cramping or blood in your stool. The CDHF² says life-impacting pain during periods, bowel movements or urination can point to endometriosis. OWH³ says to talk with a doctor or nurse if over-the-counter medicine doesn’t help or pain interferes with daily activities, and lists blood clots larger than a quarter among the signs to mention. Our articles on endometriosis and heavy periods cover those.

Book an appointment if any of these fit:

• Blood in your stool
• Pain with bowel movements or with peeing during your period
• Cramps that medicine doesn’t touch, or that keep you from work or school
• Clots larger than a quarter
• Symptoms that have changed or gotten worse over time

A loose stool or two on day one is your uterus and bowel working off the same signal. Pain that sends you to bed is a separate question, and it has answers.