Introduction
It seems like no matter what you eat, your stomach feels full and stretched, maybe even swollen, even if you’ve barely eaten. If you’re asking “why am I always bloated,” you’ve probably already blamed gas and started cutting foods.
But it turns out multiple causes could be contributing to your bloating, and discovering yours requires some careful consideration. Below, I’ve listed out seven overarching causes, along with a four-step checklist that can help you determine what’s causing your bloat.
Bloating vs. Distension: What’s the Difference?
A lot of people think of a bloated stomach and picture a belly that’s physically larger. But that’s not necessarily the case. A 2025 European consensus statement on bloating defines it as a “sensation of abdominal fullness and discomfort, which may or may not be accompanied by distension.” Abdominal distension is the term for an actual visible swell of your belly. You don’t have to see visible swelling in order to experience bloating. People often describe bloating as fullness, pressure, tightness, or “being inflamed.”
Bloating and distension don’t always appear together. In one study, women with IBS wore a sensor around their waist for 24 hours. Only about half of those who felt bloated actually had measurable swelling. That could mean that bloating and distension have two different causes.
Is It Normal to Be Bloated Every Day?
Occasional bloating is common and can happen to anyone. Nearly 1 in 5 adults worldwide say they’re bloated at least once a week, and women are about twice as likely as men to report it.
When bloating is your main problem, doctors call it functional bloating. It shows up at least one day a week for the last 3 months, started at least 6 months ago, and can’t be better explained by another gut disorder like IBS or chronic constipation.
If you experience bloating every day, that’s well past the line. It’s common, but it isn’t something that you have to accept as normal. Because IBS and constipation can show up in similar ways, your self-check should begin by ruling those out.
Common Causes of Bloating
Gas can play a part in bloating.
Gas enters your GI tract when you swallow air, or it can be freed up from food as it’s digested, diffused in from the blood, or produced by the microbiome. It exits in the opposite ways: burping, passing gas, diffusion into the blood, or being consumed by the microbiome.
But gas isn’t always the entire story. Bloating can come from seven main causes, and many people have more than one:
- Food your body doesn’t fully absorb
- Gut bacteria making extra gas
- Swallowed air
- A slow gut
- A sensitive gut
- A belly and diaphragm out of sync
- Hormonal fluctuations
1. Food your body doesn’t fully absorb
When we eat foods, they meet proteins in our gut called enzymes. These enzymes break foods down into their core parts so the nutrients can be absorbed. Some people have enzyme deficiencies, meaning they can’t fully break down some carbs. When these carbs go undigested, water gets drawn towards them, which builds up pressure in the gut. When they reach the colon, they’re fermented by the microbiome, which creates gas.
This is what happens in food intolerances, like lactose intolerance. Sugar alcohols like sorbitol, found in many sugar-free products, can do the same. So can fructans, a carb found in wheat.
The simplest way to test for a food intolerance is to cut the food for 2 weeks. If your symptoms get better, that’s a sign you may not tolerate that food well.
Some medical conditions can cause the same problem. Crohn’s disease, celiac disease, and pancreatic exocrine insufficiency (when the pancreas doesn’t make enough digestive enzymes) can all keep carbs from being absorbed. Celiac disease and inflammatory bowel disease (IBD) also inflame the gut lining, which can add to bloating on its own.
2. Gut bacteria making extra gas
It’s possible your gut microbiome produces too much gas, even on a normal food intake. The European consensus points to “dysbiosis,” which just refers to a microbiome that’s altered from normal. An altered microbiome might produce gases in different, excessive amounts. It’s hard to pin down this cause for certain, though, since no one has defined what a normal microbiome looks like.
Perhaps the most notorious version of this is SIBO, small intestinal bacterial overgrowth. It means there are too many bacteria in the small intestine, which normally has relatively few. SIBO is more likely in people who’ve had bowel surgery, have a motility disorder (a gut that moves too slowly), or have taken acid-reducing medication long term. These can let bacteria build up in the small intestine. In those people, bloating is common. But does SIBO explain everyday bloating in people without these risk factors? That’s one of the most disputed questions in gut health, and it’s still unproven.
3. Swallowed air
Rushing through a meal, chewing gum, using straws, and fizzy drinks are commonly blamed for swallowing extra air. It’s possible this extra air adds to the pressure you feel.
4. A slow gut
Your gut is a muscular tube that contracts to keep its contents moving. When the gut moves its contents slowly (known as “altered motility”), gas and stool can build up instead of clearing, which adds pressure and bloating. Over 90% of people with chronic constipation report bloating. And, people whose colon moves stool more slowly tend to visibly swell more.
Constipation comes in two main types, and they can overlap:
- A slow colon. Stool moves through too slowly, so you go less often and it comes out hard and lumpy.
- An emptying problem. Stool reaches the end of the tract, but doesn’t fully come out. A common reason for this is that the pelvic floor muscles tighten instead of relax when you push, so the bowels don’t fully empty. Fiber and laxatives often don’t help this type, because the problem is with muscle coordination, not stool. This type should be treated with pelvic-floor therapy.
In one study, 64% of people who had severe bloating that didn’t improve after 2 weeks of dietary advice failed a test that measured how well they could push stool out from their rectum. This suggests that for some people, bloating may have less to do with diet and more to do with how well their bowels empty.
A slow gut can also be caused by other conditions. An underactive thyroid (hypothyroidism) can slow down your gut and digestion, which can lead to a buildup of contents within the gut. Diabetes can damage nerves, including the vagus nerve, which helps control how your gut contracts and digests. These two are the most common hormone-related conditions linked to bloating.
5. A sensitive gut
Sometimes, gas isn’t the entire story.
In one study that CT-scanned people while they were bloated, only about 1 in 4 had more gas than normal.
Another study had people with and without IBS drink the same amount of a fermentable carb, which gut bacteria turn into gas. The two groups made about the same amount of gas, but the IBS group reported feeling it a lot more.
So why would the two groups have two entirely different experiences? The answer could be visceral hypersensitivity.
Normally, pain receptors in your gut look out for threats. If these pain receptors become excited enough, they send signals to your brain, which is when you feel pain. In visceral hypersensitivity, these pain receptors activate even when nothing is wrong. So what causes these signals to get out of balance? There are two main possibilities:
- Immune activity in the gut wall could sensitize your pain receptors to react to things that normally don’t hurt.
- How your brain reads the signals. Work-related or social stress, anxiety, or depression can heavily affect how the brain and spinal cord process gut signals, so your brain may read normal signals as painful. Diabetes can change this processing too.
6. A belly and diaphragm out of sync
Normally, when you eat food and your gut fills up, the diaphragm (the dome-shaped muscle under your lungs) relaxes upward to make room. At the same time, your abdominal wall (your abs) will tighten up. In people who visibly swell and feel bloated, the opposite occurs: the diaphragm contracts and pushes down on your belly, and your abs relax so your belly gets pushed out.
Researchers call this abdomino-phrenic dyssynergia: a belly and diaphragm out of sync.
In one small study, researchers scanned people’s bellies during a bad bloating episode. In people with a severe motility disorder, the belly really filled up. But in people with functional bloating, the volume barely changed. Their diaphragm dropped down and pushed their belly out.
No one knows why this happens, but it could have to do with how your nervous system reacts to signals from a sensitive gut. Early research suggests that this reflex can be retrained over time.
7. Hormonal fluctuations
For women, shifts in sex hormones are worth considering. Hormones shift during the menstrual cycle, pregnancy, and menopause, and with conditions like endometriosis or polyendocrine metabolic ovarian syndrome (PMOS, formerly called PCOS).
Changes in estrogen and progesterone may slow your gut, change your microbiome, and increase water retention, all of which can aggravate bloating. In one study that followed almost 300 midlife women, bloating got worse during the transition to menopause.
Bloating before your period is common in healthy women and usually not cause for alarm. But if it gets worse before and during your period month after month, it may point to endometriosis.
In one study, women with endometriosis had much worse abdominal pain, constipation, and bloating than women without it. They also said their gut symptoms affected their lives more.
If your bloating comes with signs like painful periods, pain during sex, painful bowel movements, excess hair growth, irregular or missed periods, or trouble getting pregnant, it could be worth asking a qualified medical professional about endometriosis or PMOS.
Why Do You Get Bloated After Eating?
If your bloating comes with meals, at night, or with foul-smelling gas, it’s likely that the gas is being made in your gut rather than swallowed.
Fried, fatty foods and large meals are known to be triggers. Fat can slow down your gut, make it more sensitive, and keep gas from moving through.
A big jump in fiber intake can contribute as well. Fiber reaches your colon undigested and gets fermented by your gut bacteria, producing gas. It’s recommended to increase your fiber intake slowly, adding about 5g a day each week.
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How to Find the Cause of Your Bloating
Going through the clues one at a time can help you narrow down the likely causes and know what to bring up with your doctor.
Step 1: Check for Warning Signs
See a doctor before you test anything at home if your bloating comes with any of these signs:
- New anemia
- Pain that wakes you up at night
- Unintentional weight loss
- Bloody stools
- Fever
- Vomiting
- Pale, greasy stools
- A family history of bowel or ovarian cancer
- Symptoms that are new or getting worse
These are signs that something else may be contributing to your symptoms. A qualified medical professional can examine you and rule out anything serious.
Step 2: Check for IBS and Constipation
Doctors rule these two out before calling bloating “functional,” because the label can change which treatment they try. See if either fits you:
- IBS: belly pain at least one day a week for the last 3 months, plus at least two of these:
- The pain changes when you have a bowel movement
- The pain comes with a change in how often you go
- The pain comes with a change in how your stool looks
- Chronic constipation: for the last 3 months, at least two of these:
- Straining most times you go
- Hard or lumpy stools
- Feeling like you haven’t fully emptied
- Feeling blocked
- Needing to press on your belly or use your fingers to go
- Fewer than 3 bowel movements a week
If one fits, the clues below may still apply.
Step 3: Match Your Clues
- Bloating follows specific foods: dairy, sugar-free sweets, wheat
- It may point to food you don’t fully absorb, like lactose, sugar alcohols, or fructans. Cut them for 2 weeks and see if your symptoms respond.
- Bloating comes with frequent loose stools, or IBD runs in your family
- May be due to inflammation of the gut lining, which could be related to celiac disease or IBD.
- Bloating comes with meals, at night, or with foul-smelling gas, or it got worse after you added fiber
- Gas is being made in your gut. Large, high-fat meals or adding too much fiber at once can be triggers.
- You’ve had bowel surgery, have a motility disorder, or take acid reducers long term
- These are risk factors for SIBO.
- Bloating comes with lots of belching or burping
- It may be due to swallowed air from eating fast, chewing gum, or fizzy drinks.
- Your bloating is worse when you’re constipated, or you deal with straining or feelings of blockage
- You may have a slow gut or an emptying problem.
- There could be potential contributions from diabetes or an underactive thyroid.
- You feel full or tight but your waist doesn’t change size
- Your bloating could be related to a sensitive gut.
- Bloating comes with stress or tension
- Your brain may be turning up or changing signals from your gut.
- Your belly visibly swells during the day and then goes back down
- Your belly and diaphragm are out of sync.
- Less often, a slow gut.
- Bloating follows your cycle, started around perimenopause, or comes with pelvic pain
- Your bloating could be related to hormone shifts, endometriosis, or PMOS if you have other hormone-related symptoms.
Step 4: Get Tested for What You Can’t Notice
Some causes only show up on tests. A workup may include blood tests for anemia and inflammation (CBC, CRP), celiac (tTG-IgA), thyroid (TSH), and blood sugar (HbA1c), plus a stool test that helps tell IBD from IBS (fecal calprotectin). If your bloating comes with indigestion, upper-belly pain, or feeling full fast, a test for H. pylori (a stomach bacterium) may be helpful. These tests can rule other conditions out, but they can’t diagnose bloating itself.
If nothing above fits and your tests come back normal, that’s called functional bloating. Oftentimes it’s related to a sensitive gut.
Are At-Home Bloating Tests Worth It?
When trying to discover the source of your bloating, it’s common to look for tests that can help explain it. Many people turn to at-home tests: breath tests for SIBO or malabsorption, microbiome tests, and food sensitivity tests.
SIBO breath tests
You drink a sugar like glucose or lactulose, and the test measures the gas you breathe out. The idea is that if gas rises within 90 minutes, bacteria must be fermenting the sugar early in the small intestine. However, there are no agreed-upon cut-offs for what counts as a positive result. And in many healthy people, lactulose can reach the colon in less than 90 minutes, so an “early” rise in gas might not indicate SIBO at all. In one study of 40 healthy adults, the lactulose test came back positive in 60%. The European consensus also states that hydrogen breath tests aren’t accurate enough to diagnose it. Up to 80% of people with IBS test “positive,” and many get prescribed antibiotics they may not need. A lactose breath test is more useful, but it shows whether you absorb lactose, not whether it’s causing your symptoms.
Microbiome tests
These tests can’t give you a clear diagnosis or treatment plan, since their testing methods differ greatly from one another. In one study, the exact same stool sample sent to seven companies came back different on each test. The difference was as much as it would have been if seven different samples were sent to seven different companies. Since results are inconsistent, the dietary and supplement advice they come with can also be inaccurate. That can lead people to make health changes they don’t need and buy supplements that won’t actually target the root cause of their symptoms.
Food sensitivity tests
Most measure IgG, an antibody your immune system makes after it’s been exposed to a food. It’s a sign of exposure, and it doesn’t mean that the food is harming you. In a study of 28,292 adults with no symptoms, more than half tested positive to an IgG test anyway.
Conclusion
So, why are you always bloated? For most people, it isn’t simply too much gas. Bloating can be caused by a number of different things. It can be from a sensitive gut, or a gut that isn’t fully clearing itself. It can be due to food your body doesn’t fully absorb, or it can be related to a medical condition. Often, several causes are blended together.
Use the four steps above to narrow down your likely causes, and take note of everything you notice. Before paying for a test, know what it can and can’t tell you. If your bloating is new and sudden, happens most days, or comes with any of the warning signs, you don’t have to wait to receive the help you need.