Bloating on your period? Here’s what your hormones have to do with it

Bloating. 

We ALL experience it now and then. If we’re being totally honest, most of us have some sort of belly bloat daily (...food baby, we’re looking at you).

But food baby fullness is only one of the many things that cause our tummies to tighten. For those of us who menstruate, we might notice that our bloating curiously crops up just before (or during) our periods each month.

Cyclical bloating is any bloating we experience as a result of hormonal (and bodily) changes, during our menstrual cycles.

In fact, cyclical bloating is SO common that it’s even #trending on TikTok... (check out the pre-period bloated belly time-lapses if you’re wondering ‘what does period bloating look like’...).

Comedic TikTok trends aside, bloating can be a seriously uncomfortable, painful, and sometimes upsetting experience—especially if our swollen stomachs are impacting our self-esteem. 

But, as always, we believe the first best step to tackling any symptom (if that’s something you want to do) is understanding it. So, let’s uncover exactly what is bloating and what have our menstrual cycles got to do with it? 

What causes bloating?

There’s definitely a mythical misconception that non-cyclical bloating (bloating not linked to our cycle) is simply a sign of a satisfied stomach.

However, constipation, food intolerances and trapped air can all contribute to tightness in our tummies. This is important because it shows that many other things can cause your bloat to balloon, such as:

• Fluid Retention: when your body holds onto more water than usual. This can happen if you are dehydrated or have eaten too much salt (1–3).
  
  

• Constipation: if your bowels are full and you haven’t been able to empty them, they might press on your stomach causing your tummy to stick out (4).
  
  

• Trapped Air: eating in a hurry, drinking a lot of fizzy drinks, or chewing gum, can all increase the amount of gas in your belly (4).
  
  

• Stress: when we are stressed, our body produces more cortisol (our stress hormone). Cortisol can disturb our digestion (5) and cause tummy cramping (4). Both of these may lead to bloating.
  
  

• Irritable Bowel Syndrome (IBS): a common gut condition swamped with symptoms like diarrhea, constipation, bloating and belly cramps (6). The cause of IBS is still not certain but stress, our genes, and sensitivities to certain foods can all influence its symptoms (6).

So, it really is tricky to completely steer clear of bloating when so many things can cause it to pop up out of the blue. It just goes to show that everyone and anyone can suffer from a swollen stomach from time to time.  

And you may now be thinking, ‘this is all good to know but my digestion is smooth, I’m not too stressed and I carry a water bottle with me everywhere I go—so why do I feel bloated on my period?’

And the answer is—our hormones (duh).

How do our hormones affect bloating?

Whether you’re a monthly menstruator or not—everyone bloats. But people with cycles experience bloating more than those without (7) (unsurprisingly because bloating pre-period is a top PMS symptom that many owners of uteri share) (2,3).

In fact, a bloated belly in your late luteal phase is often a sign, or a physical cue,  that your bleed is due (9) (kinda like your womb’s way of saying, ‘let’s get shreddy’). 

In a predictable pattern, just as you start cramping and your head starts hurting, bloating is another pre-period party pooper. 

It’s fluctuations in our female sex hormones, estrogen and progesterone, throughout our cycles, that disturb our digestion and trigger bloating (8,9). There’s often crossover between the causes, but here are some of the changes that varying estrogen and progesterone levels around our bleeds may bring about to cause bloating:

Constipation

Higher levels of progesterone before our periods may cause constipation (9). 

As well as progesterone’s important role in maintaining our womb walls, when its levels are high (before our bleeds) this can reduce the contractions of muscles in the linings of our stomachs and intestines (11). 

These muscles are really important for moving things along, so when they contract less frequently this can slow the rate that food leaves our stomachs and delay the emptying of our bowels (12). 

And if we’re stalled up with stools, our bowels can push against our stomach muscles, causing some painful bloating (13). 

Then when progesterone plummets, these muscles increase their contractions causing our womb lining to shed (hello period) but also helping to empty the contents of our stomachs and restore some healthy bowel movements once again! This means our bloating should subside a couple of days after we start bleeding (8).

Increased Appetite

Together with progesterone, higher levels of our stress hormone (cortisol) in the late luteal phase of our cycles (14,15) may be part of the reason why we feel more anxious and experience funny food cravings tied with a surge in our appetites before our monthly bleeds (4,14–16). 

Our increased appetite is like mother nature’s reminder to eat more in preparation for possible pregnancy (or period) and any bloating that comes with curious cravings and food baby fullness is warmly welcomed for what our wombs are about to go through next.

Familiar with fight and flight? Well congrats cortisol, your period preparation is mighty fine.

Fluid Retention

Oh and higher levels of our progesterone and cortisol not only increase our appetites, but they also cause our body to hold onto more water than usual (known as fluid retention) (8,17). 

Similarly, our pre-period estrogen peak has a similar effect in filling us with fluid too (8). Then, when these hormone levels fall (providing we are not pregnant) they trigger the beginning of our bleed and any premenstrual fluid retention we may have had, should subside. 

But how do these hormones cause fluid retention to happen?

High levels of progesterone, estrogen, and cortisol around our periods can increase our cravings for salty snacks and this may lead to more salt in our blood (16,18). Water then moves out of our tissues and into the blood to balance out the salt in our circulation (17). It is this increased fluid outside of our tissues that might provide us with some pre-period puffiness.

So, with all these factors coming into play, bloating on (and around) your period may seem hard to handle but we believe there are a few ways to alleviate some of the swollen stomach symptoms you may be suffering with.

So essentially, if you’re wondering ‘is bloating a sign of my period’, then yep, you’ve hit the nail on the head hunny.

What can help my bloating?

• Slowing down when your eating and drinking:
  Eating and drinking slower will reduce how much air you swallow. Try to stick to foods you know work with you, if you notice you're getting particularly poppy after certain foods, they probably don't agree with you.

• Holding back on bubbly beverages:
  If you consider yourself a fizzy drink fanatic, limiting your consumption of bubbles could help to alleviate some of your belly bloating (20).

• Exercising regularly:
  This may be more difficult in the week leading up to your period (when you feel more like a duvet day than exploring the great outdoors) but going for a stroll, or getting out and about at least once a day, could really help get things moving down there and alleviate some of your discomfort (21).

• Staying sensible with salt:
  Being more aware of your salty snack cravings before your bleed may help to reduce how much salt you eat and ease some of the fluid retention you're feeling (3). 

How can Tuune help?

Want to know if your bloating is being brought on by your hormones? We can help track when your bloating balloons (and when it subsides) to figure out if your pre-period progesterone and elevated estrogen have anything to do with it.

And if your bloating appears to be cyclical, taking birth control pills continuously (with no hormone-free break) may help (21). Studies have shown that taking birth control pills this way can smooth and stabilize the peaks in your progesterone and estrogen that lead to pre-period bloating (21). 

But because we’re all wonderfully unique (and so our hormones are too) we won’t all experience similar improvements in our swollen stomach symptoms on the same pill. 

By monitoring your symptoms throughout your cycle, and tracking how they change on birth control types you have previously tried, your pre-period puffiness may not have to be a PMS problem. There may be a way to keep your bloating at bay like finding the right birth control for you.

Written by

Hannah Durrant (she/her)

Hannah is a Biomedical Content Writer at Tuune, with a BSc in Biomedical Sciences from University College London. She is passionate about bringing together the scientific community and the general public by disseminating modern science via digestible, engaging and thought-provoking content.

Medically reviewed by

Dr. Arushee Prasad, GP, MBBS (she/her)

Dr Arushee Prasad is a GP for NHS England with an MBBS in Medicine and Surgery, and an MRCGP from the Royal College of General Practitioners. Passionate about digital health and algorithmic medicine, Arushee was previously an Algorithmic Medical Doctor for Docly.