Bloating Before Your Period, and in Perimenopause: What Studies Show

Some months your waistband tightens on a schedule that has nothing to do with dinner. Research backs up the pattern.

How common it is

A Canadian survey asked 156 healthy women with no gut or gynecological diagnosis about symptoms around their periods.¹

Symptom	5 days before period	During period
Bloating	62%1	51%1
Belly pain	58%1	55%1
Diarrhea	24%1	28%1

Bloating was the most common gut symptom overall.¹ Women who also reported low mood had more bloating during their period: 82% versus 52%.¹ The women reported from memory, at one clinic.¹

If you have IBS

In 29 women with IBS, belly pain and bloating were worse during the period than at most other points in the cycle, and the gut became more sensitive to stretching then too.² The same team had found no such change in healthy women.² So with IBS, the same amount of gas may simply feel like more during your period.

Why it happens, and what it has to do with perimenopause

A review of 18 papers found that gut symptoms, including bloating, tend to flare before and during periods and in perimenopause, times when estrogen and progesterone are falling or low.³ The authors suggest that hormone withdrawal may play a part, and say it still needs confirming.³ We found no study that tracked bloating across perimenopause directly.

What to do with the pattern

1. Log cycle day next to your bloating for two cycles, with day 1 as the first day of your period, even if cycles are irregular.
2. Circle your three worst bloating days each month and see whether they cluster before day 1.
3. If they cluster, time any change you try across a full cycle before judging it.
4. If they don’t, the calendar probably isn’t the main driver. See why your stomach gets bigger through the day and why you have so much gas.

Monthly bloating with painful periods is worth raising with a gynecologist; see what endometriosis is. New, frequent bloating after 50 is a different situation: see new bloating after 50.

Try: “I’m 47 and I bloat badly for about five days before each period, and my periods are getting irregular. Could this be hormonal, and is there anything worth checking?”

Bloated by Dinner covers this in Chapter 6, “Pregnant by Dinner,” in a section called “Before Your Period.” Its Belly Clock has a column for cycle day, so a monthly pattern stands out even when your cycle is irregular. See the book.