Bloating is one of the most common digestive complaints, reported by 10-30% of adults. While occasional bloating after a large meal or certain foods is normal, chronic or severe bloating that doesn’t respond to dietary changes often signals something more than just “eating too much” or “gas.”

The digestive system is influenced by hormones, immune function, the gut microbiome, and overall metabolic health. Conditions like celiac disease, thyroid dysfunction, ovarian problems, and small intestinal bacterial overgrowth can cause persistent bloating. Blood tests can help identify many of these underlying causes, pointing the way toward effective treatment rather than endless dietary restriction.

This article explores what’s actually happening when you feel bloated and what blood tests can reveal about chronic abdominal distension.

Understanding Bloating

Bloating refers to the subjective sensation of abdominal fullness, pressure, or tightness — a feeling that your belly is swollen or “too full.” It’s one of the most common digestive complaints, reported by 15-30% of the general population and up to 90% of people with irritable bowel syndrome (IBS).

Bloating is often — but not always — accompanied by visible abdominal distension (the belly actually getting larger and measurably increasing in girth). These two symptoms can occur together or independently, and distinguishing between them helps guide diagnosis and treatment.

Bloating versus distension:

Bloating is the feeling — the subjective sensation of being too full, swollen, pressurized, or tight in the abdomen. It’s what you experience and report. Bloating can be present even without any measurable changes in abdominal size.

Distension is the physical finding — an actual, objective increase in abdominal girth that can be measured with a tape measure. The abdomen visibly protrudes more than usual. Studies using abdominal imaging have confirmed that some people have significant distension (several centimeters of expansion) by evening compared to morning.

Many people experience both — they feel bloated and their abdomen measurably expands (often worse in the evening than morning). But the patterns can differ:

• Bloating without significant distension: Often relates to visceral hypersensitivity — the gut nerves are extra-sensitive to normal amounts of gas, fluid, or intestinal distension. The gut-brain communication is amplified, so normal sensations are perceived as uncomfortable or painful. This pattern is common in irritable bowel syndrome (IBS) and functional dyspepsia.
• Distension without much bloating sensation: May indicate actual accumulation of material in the abdomen — fluid (ascites), fat, masses, or significant gas accumulation. Some people develop substantial distension without perceiving it as particularly uncomfortable until it becomes severe.
• Both bloating sensation and visible distension: Can indicate excess gas production (from bacterial fermentation, food intolerances, or SIBO), slowed gut transit (from hypothyroidism, diabetes, or medications), fluid retention, or conditions affecting both sensation and actual gut contents.

What causes the sensation of bloating:

Multiple mechanisms contribute to bloating, often in combination:

• Excess gas production: Gut bacteria ferment dietary carbohydrates, producing hydrogen, carbon dioxide, methane, and other gases. Excess gas can result from:
  • Consuming fermentable carbohydrates (FODMAPs, fiber, certain sugars)
  • Small intestinal bacterial overgrowth (SIBO), where bacteria are present in high numbers in the small intestine
  • Malabsorption (as in celiac disease or lactose intolerance), where unabsorbed nutrients reach the colon and are fermented
  • Altered gut microbiome composition
• Impaired gas transit and evacuation: Even with normal gas production, if gas doesn’t move through and out of the gut efficiently, it accumulates. People with IBS often have impaired gas transit — the gas that’s produced doesn’t move through as quickly as it should.
• Swallowed air (aerophagia): Eating quickly, talking while eating, chewing gum, drinking through straws, and drinking carbonated beverages all increase swallowed air. Anxiety can also lead to excessive air swallowing.
• Fluid retention: Hormonal fluctuations (particularly around menstruation and menopause), heart failure, liver disease (ascites), and kidney disease can all cause fluid accumulation in the abdomen or throughout the body.
• Slowed gut motility: When food moves slowly through the digestive tract, it has more time to ferment and produce gas. Additionally, slow transit allows more water absorption, contributing to constipation and distension. Conditions causing slow motility include hypothyroidism, diabetes (diabetic gastroparesis), certain medications (opioids, anticholinergics), and neurological conditions.
• Abnormal gut-brain interaction (visceral hypersensitivity): In functional GI disorders like IBS, the gut nerves are hypersensitive — normal amounts of gas, stool, or distension that wouldn’t bother most people are perceived as uncomfortable, painful, or intolerable. This is a real physiological phenomenon, not “just in your head.”
• Abnormal diaphragm and abdominal wall muscle function: Research has shown that some people with bloating have abnormal relaxation of the diaphragm and contraction of abdominal wall muscles after eating, essentially “pushing out” the abdomen. This can occur even without excessive gas.
• Malabsorption: When nutrients aren’t properly absorbed in the small intestine (as in celiac disease, pancreatic insufficiency, or after certain surgeries), unabsorbed material reaches the colon where bacteria ferment it, producing gas and drawing in fluid.
• Dysbiosis: An imbalance in the gut microbiome — too many of certain bacteria, too few of others — can lead to excess gas production, altered gut motility, and increased intestinal permeability.
• Physical obstruction or pseudo-obstruction: Anything physically blocking normal flow through the intestines (strictures, adhesions, tumors) or functional obstruction (intestinal pseudo-obstruction) can cause backup, distension, and bloating.

Patterns that suggest different causes:

Bloating that worsens throughout the day — minimal in the morning, progressively worse as the day goes on, and improving overnight — is very common. This pattern often relates to eating patterns (cumulative effect of meals), gas accumulation, posture (upright during the day allows gravity effects), and normal circadian variation in gut function. May be functional (IBS) or related to slow transit, food intolerances, or SIBO.

Bloating after specific foods — predictably worsening after consuming certain foods — suggests food intolerance (lactose, fructose, FODMAPs, gluten) or conditions like celiac disease. Keeping a food and symptom diary can help identify patterns.

Bloating with diarrhea — loose, frequent stools along with bloating — may indicate celiac disease, inflammatory bowel disease (IBD), infection, or SIBO. The combination suggests malabsorption or inflammation.

Bloating with constipation — infrequent or difficult bowel movements along with bloating — often indicates slow transit, inadequate fiber and fluid, hypothyroidism, medication effects, or IBS-C (constipation-predominant IBS). Stool backing up in the colon causes distension.

Bloating that’s relatively constant — doesn’t fluctuate much with meals, time of day, or bowel movements — is more concerning and may indicate ascites (fluid accumulation), a mass, ovarian pathology, or other structural problem. This pattern warrants prompt evaluation.

Bloating with weight loss is an alarm symptom that requires prompt evaluation. The combination may indicate malignancy, malabsorption (celiac disease, pancreatic insufficiency), or inflammatory conditions.

Bloating with early satiety — feeling full very quickly after starting to eat — suggests gastroparesis (delayed stomach emptying), a gastric outlet obstruction, or an upper abdominal mass.

When bloating suggests an internal cause:

Occasional bloating after eating too much, consuming gas-producing foods (beans, cruciferous vegetables, onions), drinking carbonated beverages, or around menstruation is completely normal and doesn’t require investigation. Bloating suggesting an underlying condition:

• Persists despite reasonable dietary modifications (eliminating common triggers like dairy, wheat, and high-FODMAP foods)
• Is severe enough to affect quality of life, daily activities, or what you’re willing to eat
• Is accompanied by other concerning symptoms (unintentional weight loss, blood in stool, persistent diarrhea, fever, severe pain)
• Represents a significant change from your baseline — you never used to bloat this way
• Is progressive — steadily getting worse over weeks to months
• Is associated with new, severe, or worsening abdominal pain
• Doesn’t respond to over-the-counter remedies that previously helped
• Is accompanied by symptoms suggesting specific conditions (hypothyroid symptoms, signs of liver disease, gynecological symptoms)

Warning signs requiring prompt evaluation:

These “red flag” symptoms warrant prompt medical evaluation:

• Unintentional weight loss (losing weight without trying)
• Blood in stool (visible red blood or black tarry stools)
• Severe or progressively worsening abdominal pain
• Persistent vomiting, especially if unable to keep down fluids
• Fever accompanying GI symptoms
• New bloating after age 50 without clear dietary explanation
• Family history of GI cancers (colon, stomach, pancreatic) or ovarian cancer
• Signs of ascites (rapid abdominal expansion, fluid wave on examination, shifting dullness)
• Jaundice (yellowing of skin or eyes)
• Palpable abdominal mass
• Signs of bowel obstruction (severe pain, vomiting, inability to pass gas or stool)

Celiac Disease: The Hidden Cause

Celiac disease is an autoimmune condition triggered by gluten (a protein found in wheat, barley, and rye) that damages the small intestinal lining. It affects approximately 1% of the population worldwide — roughly 1 in 100 people — but the majority of cases remain undiagnosed. Many people with celiac disease don’t know they have it, and bloating is one of its most common presenting symptoms.

Celiac disease is dramatically underdiagnosed because its symptoms are often attributed to other conditions (particularly IBS), because it can present subtly or atypically, and because many healthcare providers don’t think to test for it. Studies suggest that for every person diagnosed with celiac disease, there are 5-10 people who have it but don’t know it.

How celiac disease causes bloating:

• Malabsorption from villous atrophy: In celiac disease, the immune response to gluten damages and eventually destroys the finger-like projections (villi) that line the small intestine and are responsible for nutrient absorption. This “villous atrophy” dramatically reduces the intestine’s absorptive surface area. When carbohydrates, fats, and other nutrients aren’t absorbed in the small intestine, they pass into the colon, where bacteria ferment them, producing hydrogen, carbon dioxide, methane, and other gases.
• Intestinal inflammation: The immune reaction causes significant inflammation in the gut wall. This inflammation disrupts normal gut motility and function, contributing to bloating and other symptoms.
• Increased intestinal permeability (“leaky gut”): Celiac disease damages the tight junctions between intestinal cells, increasing intestinal permeability. This allows partially digested food particles and bacterial products to interact with the immune system, perpetuating inflammation.
• Altered gut microbiome: Celiac disease is associated with significant changes in the composition of gut bacteria (dysbiosis). This altered microbiome may contribute to excess gas production and abnormal fermentation patterns.
• Secondary lactose intolerance: Lactase, the enzyme that digests lactose (milk sugar), is produced in the tips of the intestinal villi. When villi are damaged, lactase production decreases dramatically, causing secondary lactose intolerance. This adds another source of bloating when dairy is consumed, and many people with undiagnosed celiac disease notice they can’t tolerate dairy (not realizing the underlying cause is celiac damage to the villi, not primary lactose intolerance).
• Pancreatic insufficiency: Some people with celiac disease develop secondary pancreatic insufficiency, further impairing digestion and contributing to malabsorption.

Characteristics of celiac-related bloating:

• Typically worsens after eating gluten-containing foods, though the connection isn’t always obvious because symptoms can be delayed by hours or even days
• Often accompanied by diarrhea — loose, pale, foul-smelling stools that may float (from fat malabsorption) — though constipation can also occur
• Frequently associated with excessive flatulence
• May have associated fatigue (often profound), which may relate to anemia, malnutrition, or the inflammatory process itself
• Can be accompanied by weight loss or difficulty maintaining weight, though not everyone with celiac disease loses weight — some are normal weight or even overweight
• Can be the only obvious GI symptom — “silent” or atypical celiac may present primarily with anemia, osteoporosis, neuropathy, or infertility without prominent GI complaints
• May have been present for years or even decades, attributed to IBS, “sensitive stomach,” or just “how I am”
• Often runs in families — if you have a first-degree relative with celiac disease, your risk is about 10%

Other celiac symptoms:

Celiac disease is a systemic condition that can affect virtually any organ system, not just the gut. Look for:

• Diarrhea, constipation, or alternating bowel habits
• Fatigue and low energy — often one of the most debilitating symptoms
• Iron deficiency anemia — often refractory to oral iron supplements because iron isn’t being absorbed
• Other nutritional deficiencies (B12, folate, vitamin D, calcium, zinc)
• Weight loss or difficulty gaining weight (though not universal)
• Bone pain, osteopenia, or osteoporosis from calcium and vitamin D malabsorption
• Dermatitis herpetiformis — an intensely itchy, blistering skin rash, usually on elbows, knees, and buttocks; this is celiac disease of the skin
• Mouth ulcers (aphthous stomatitis)
• Dental enamel defects
• Joint pain (arthralgia)
• Neurological symptoms — peripheral neuropathy (numbness, tingling), ataxia (balance and coordination problems), headaches
• Reproductive issues — infertility, recurrent miscarriage, delayed puberty
• Depression, anxiety, irritability
• Elevated liver enzymes (transaminases) of unexplained cause

Many people with celiac disease have been diagnosed with IBS for years before the correct diagnosis is made. Studies show an average delay of 6-10 years from symptom onset to celiac diagnosis. If you have chronic bloating, especially with any of the other suggestive symptoms listed above, celiac testing is essential — it’s a simple blood test that can be life-changing if positive.

Who should be tested for celiac disease:

• Anyone with chronic unexplained bloating, especially with diarrhea
• Anyone with IBS symptoms (celiac disease should be ruled out in all IBS diagnoses)
• Unexplained iron deficiency anemia, especially if refractory to treatment
• Unexplained osteoporosis or low bone density
• First-degree relatives of people with celiac disease
• Type 1 diabetes (increased celiac risk)
• Autoimmune thyroid disease (associated condition)
• Down syndrome, Turner syndrome, Williams syndrome (increased risk)
• Unexplained elevated liver enzymes
• Unexplained neurological symptoms
• Unexplained infertility or recurrent miscarriage

What to test:

tTG-IgA (Tissue Transglutaminase IgA) is the primary screening test for celiac disease, with sensitivity and specificity above 95% in most studies. Elevated levels strongly suggest celiac disease and should lead to small intestinal biopsy for confirmation.

Total IgA should be checked simultaneously because approximately 2-3% of people with celiac disease have selective IgA deficiency. In IgA deficiency, the tTG-IgA will be falsely negative because the person can’t make IgA antibodies. If total IgA is low, IgG-based tests must be used instead.

If IgA is deficient, tTG-IgG and DGP-IgG (Deamidated Gliadin Peptide IgG) are alternative tests.

Critically important: You must be eating gluten regularly (at least a few servings daily for several weeks) for celiac blood tests to be accurate. If you’ve already gone gluten-free — as many people with GI symptoms try — the antibody levels will drop and the test will be falsely negative. If you’ve already eliminated gluten, discuss with your healthcare provider about a “gluten challenge” (reintroducing gluten before testing) or genetic testing as an alternative approach.

Thyroid Dysfunction

Both hypothyroidism and hyperthyroidism can cause bloating, though through different mechanisms. Thyroid disorders are common and often underdiagnosed, making thyroid testing worthwhile in anyone with persistent GI symptoms.

Hypothyroidism and bloating:

Hypothyroidism (underactive thyroid) slows metabolism throughout the body, including the digestive system:

• Slowed gut motility: Low thyroid hormone reduces the strength and frequency of intestinal contractions. Food moves slowly, allowing more time for bacterial fermentation and gas production.
• Constipation: Slow transit leads to constipation, and constipation itself causes bloating as stool accumulates.
• Reduced gastric emptying: Food stays in the stomach longer, contributing to fullness and early satiety.
• Fluid retention: Hypothyroidism can cause a type of swelling called myxedema, where mucopolysaccharides accumulate in tissues, though this more commonly affects the face and extremities.
• Altered gut microbiome: Thyroid function affects the composition of gut bacteria.

Characteristics of hypothyroid-related bloating:

• Develops gradually as thyroid function declines
• Associated with constipation (a hallmark of hypothyroidism)
• Slow onset — may have been building for months or years
• Doesn’t clearly relate to specific foods
• Accompanied by other hypothyroid symptoms

Other hypothyroidism symptoms:

• Fatigue and low energy
• Constipation
• Weight gain
• Feeling cold
• Dry skin and hair
• Brain fog
• Depression
• Muscle weakness

Hyperthyroidism and GI symptoms:

Hyperthyroidism (overactive thyroid) speeds up metabolism and gut motility, more commonly causing diarrhea than bloating. However, some people experience bloating along with frequent bowel movements.

What to test:

TSH is the primary screening test for thyroid dysfunction.

Free T4 and Free T3 measure thyroid hormone levels.

TPO antibodies identify autoimmune thyroid disease (Hashimoto’s thyroiditis).

Small Intestinal Bacterial Overgrowth (SIBO)

SIBO occurs when excessive bacteria colonize the small intestine, where bacterial populations should normally be relatively low (unlike the colon, which is teeming with bacteria). When bacteria are present in abnormal numbers in the small intestine, they ferment carbohydrates that would normally be absorbed higher in the gut, producing hydrogen, methane, and other gases that cause significant bloating.

SIBO is increasingly recognized as a common cause of chronic bloating and other IBS-like symptoms. Some studies suggest that a significant proportion of people diagnosed with IBS may actually have SIBO as the underlying cause.

How SIBO causes bloating:

• Bacterial fermentation in the wrong place: When bacteria normally confined to the colon colonize the small intestine, they ferment carbohydrates before those nutrients can be absorbed. This produces large amounts of hydrogen and other gases in the upper gut, causing distension and bloating.
• Methane production: Some bacteria (archaea, specifically) produce methane rather than hydrogen. Methane has a distinct effect — it slows gut transit, leading to constipation along with bloating. People with methane-predominant SIBO often have constipation rather than diarrhea.
• Malabsorption: Bacterial overgrowth can damage the small intestinal lining (villous blunting) and compete with the host for nutrients, causing malabsorption. Unabsorbed nutrients are then fermented, producing more gas.
• Bile acid deconjugation: Bacteria can deconjugate bile acids, impairing fat absorption and causing fatty diarrhea.
• Intestinal inflammation: Bacterial overgrowth triggers an inflammatory response that further disrupts gut function.

Risk factors for SIBO:

SIBO doesn’t usually occur in healthy guts — certain conditions predispose to bacterial overgrowth:

• Low stomach acid: Stomach acid kills many bacteria before they reach the small intestine. Conditions or medications that reduce stomach acid — aging, atrophic gastritis, pernicious anemia, chronic use of proton pump inhibitors (PPIs) — increase SIBO risk.
• Slow gut motility: Normal gut motility includes “housekeeping” waves (the migrating motor complex) that sweep bacteria out of the small intestine between meals. Conditions that slow motility — diabetes (gastroparesis and diabetic enteropathy), hypothyroidism, scleroderma, opioid use, post-surgical states — allow bacteria to accumulate.
• Structural abnormalities: Strictures (from Crohn’s disease, radiation, or surgery), adhesions, small bowel diverticula, or blind loops from surgery can create stagnant areas where bacteria proliferate.
• Ileocecal valve dysfunction: The valve between the small intestine and colon normally prevents backflow of bacteria from the colon. If this valve is compromised (removed, incompetent, or diseased), colonic bacteria can reflux into the small intestine.
• Immune deficiency: Immunoglobulin deficiencies and other immune problems reduce the body’s ability to control bacterial populations.
• Chronic pancreatitis: Impaired pancreatic function affects digestion and gut ecology.
• Previous GI surgery: Surgeries affecting the stomach, small intestine, or ileocecal valve can predispose to SIBO.

Characteristics of SIBO-related bloating:

• Often begins relatively soon after eating (within 30-90 minutes), as bacteria in the upper gut quickly ferment the arriving food
• May worsen with specific carbohydrates — simple sugars, starches, and fermentable fiber can be particularly problematic
• Can be accompanied by diarrhea (hydrogen-predominant SIBO), constipation (methane-predominant SIBO), or alternating patterns
• Often associated with excessive gas and flatulence
• May have nutritional deficiencies despite adequate diet — B12 deficiency is particularly associated with SIBO (bacteria consume B12)
• Symptoms may partially respond to antibiotics (temporarily), then return
• Often overlaps with or is mistaken for IBS

Testing for SIBO:

SIBO is typically diagnosed with breath testing rather than blood tests. After ingesting a test sugar (glucose or lactulose), you breathe into collection tubes at timed intervals. If bacteria are present in the small intestine, they ferment the sugar and produce hydrogen and/or methane, which is absorbed into the blood and exhaled in the breath.

However, blood tests have important roles in SIBO evaluation:

Vitamin B12 — bacteria consume B12, and deficiency is common in SIBO. Low B12 in someone with bloating and risk factors for SIBO supports the diagnosis.

Ferritin and iron — iron deficiency can occur from malabsorption or bacterial competition.

Vitamin D — fat-soluble vitamin deficiency may occur due to impaired fat absorption.

Folate — interestingly, folate may be normal or even elevated in SIBO because bacteria can produce folate.

Albumin and total protein — may be low if protein malabsorption is significant.

Food Intolerances

Food intolerances — different from food allergies — are a major cause of bloating. They occur when the body has difficulty digesting certain components of food, leading to fermentation and gas production.

Lactose intolerance:

Lactose intolerance is the inability to digest lactose, the sugar in milk and dairy products. It affects about 65-70% of the world’s adult population (though prevalence varies greatly by ethnicity).

• Lactose reaches the colon undigested, where bacteria ferment it, producing gas
• Symptoms typically occur 30 minutes to 2 hours after consuming dairy
• Bloating, gas, cramping, and diarrhea are common
• Can be primary (genetic decline in lactase enzyme) or secondary (from intestinal damage, as in celiac disease)

Fructose malabsorption:

Some people have limited ability to absorb fructose (fruit sugar), especially when consumed in excess of glucose.

• High-fructose foods include apples, pears, honey, high-fructose corn syrup
• Symptoms similar to lactose intolerance
• More common than often recognized

FODMAPs:

FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are a group of short-chain carbohydrates that are poorly absorbed and rapidly fermented by gut bacteria.

• Found in many healthy foods: wheat, onions, garlic, legumes, certain fruits
• A low-FODMAP diet can significantly reduce bloating in susceptible individuals
• Often helpful in IBS

Blood tests don’t directly diagnose food intolerances (breath tests and elimination diets are used), but they can rule out conditions that cause similar symptoms.

Ovarian Conditions

In women, persistent bloating that doesn’t respond to dietary changes should prompt consideration of ovarian pathology. The ovaries are located in the pelvis, and ovarian masses or conditions can cause abdominal distension and a sensation of bloating.

Ovarian cancer:

Ovarian cancer is often called the “silent killer” because early symptoms are vague and easily attributed to other causes. Persistent bloating is actually one of the most common early symptoms.

Warning signs that should prompt evaluation:

• Bloating that’s persistent (present most days) rather than intermittent
• Feeling full quickly when eating (early satiety)
• Pelvic or abdominal pain
• Urinary symptoms (urgency, frequency)
• Changes in bowel habits
• Unintentional weight loss

These symptoms, especially when new and persistent, warrant evaluation with pelvic examination and imaging.

Ovarian cysts:

Ovarian cysts are fluid-filled sacs that are common and usually benign. Large cysts can cause bloating, pelvic pressure, and discomfort.

What to test:

CA-125 is a tumor marker that can be elevated in ovarian cancer. However, it’s not a good screening test because it can be elevated in many benign conditions and normal in early ovarian cancer. It’s most useful in conjunction with imaging and clinical evaluation.

If ovarian pathology is suspected, imaging (transvaginal ultrasound) is more informative than blood tests alone.

Liver Disease

The liver plays crucial roles in digestion and metabolism. Liver disease can cause bloating through several mechanisms, most notably the development of ascites (fluid accumulation in the abdomen).

How liver disease causes bloating:

• Ascites: In advanced liver disease (cirrhosis), increased pressure in the portal venous system and reduced albumin production lead to fluid accumulation in the abdominal cavity. This causes progressive abdominal distension.
• Impaired digestion: The liver produces bile needed for fat digestion. Liver disease can impair bile production and flow, leading to malabsorption and bloating.
• Altered gut microbiome: Liver disease is associated with bacterial overgrowth and dysbiosis.

Signs of liver-related bloating:

• Progressive distension that doesn’t fluctuate much with meals
• Fluid wave on examination
• Leg swelling (edema)
• Jaundice (yellowing of skin and eyes)
• Spider angiomas (small red blood vessel clusters)
• History of heavy alcohol use, hepatitis, or known liver disease

What to test:

ALT and AST — liver enzymes indicating liver cell damage.

Albumin — low albumin indicates reduced liver synthetic function and contributes to ascites.

Bilirubin — elevated in liver disease, causing jaundice.

GGT and ALP — elevated in cholestatic liver disease.

PT/INR — prolonged clotting time indicates impaired liver function.

Heart Failure

Heart failure can cause abdominal bloating through fluid retention. When the heart can’t pump efficiently, fluid backs up in the venous system, leading to swelling in the legs and sometimes ascites.

Characteristics:

• Bloating associated with leg swelling
• Shortness of breath, especially when lying flat or with exertion
• Weight gain from fluid retention
• Fatigue
• Known heart disease or risk factors

What to test:

BNP or NT-proBNP — elevated in heart failure.

Diabetes

Diabetes can cause bloating through its effects on gut motility. Diabetic autonomic neuropathy — nerve damage affecting the digestive system — slows gastric emptying (gastroparesis) and intestinal transit.

How diabetes causes bloating:

• Gastroparesis: Delayed stomach emptying causes food to sit in the stomach longer, producing fullness, bloating, and nausea.
• Slowed intestinal transit: Slow movement through the intestines allows more time for fermentation.
• Altered gut microbiome: Diabetes is associated with changes in gut bacteria.

What to test:

Fasting glucose and HbA1c

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) — Crohn’s disease and ulcerative colitis — causes inflammation in the digestive tract that can lead to bloating along with other symptoms.

Characteristics:

• Bloating often accompanied by diarrhea (often bloody in ulcerative colitis)
• Abdominal pain and cramping
• Fatigue
• Weight loss
• May have extraintestinal manifestations (joint pain, skin problems, eye inflammation)

What to test:

CRP (C-Reactive Protein) and ESR — markers of inflammation.

CBC — may show anemia, elevated white blood cells, or elevated platelets.

Albumin — may be low in active disease.

Stool tests (fecal calprotectin) and endoscopy are needed for definitive diagnosis.

The Testing Strategy for Bloating

When bloating is chronic, severe, or accompanied by other symptoms, blood tests can help identify underlying causes.

Core tests for unexplained bloating:

Celiac screening:

• tTG-IgA
• Total IgA

Thyroid function:

• TSH

Inflammatory markers:

• CRP
• CBC

Liver function:

• ALT
• AST
• Albumin

Metabolic:

• Glucose

Additional tests based on clinical picture:

• If IBD suspected: CRP, ESR, albumin, stool calprotectin
• If heart failure suspected: BNP
• If ovarian pathology suspected in women: CA-125 (with imaging)
• If SIBO suspected: B12, iron studies (with breath test)
• If nutritional deficiencies suspected: B12, folate, iron, vitamin D

What to Do With the Results

If celiac disease is found:

A strict gluten-free diet is the treatment. Bloating typically improves significantly within weeks to months of eliminating gluten. The intestinal lining heals, absorption normalizes, and symptoms resolve. Working with a dietitian experienced in celiac disease helps ensure complete gluten elimination.

If hypothyroidism is found:

Thyroid hormone replacement typically improves GI symptoms including bloating as metabolism normalizes and gut motility increases. Constipation often improves first, with bloating following.

If liver disease is found:

Management depends on the cause and severity. Ascites from cirrhosis requires sodium restriction, diuretics, and treatment of the underlying liver disease. In severe cases, procedures to remove fluid (paracentesis) may be needed.

If inflammatory markers are elevated:

Further evaluation for inflammatory conditions (IBD, infections, autoimmune conditions) is warranted, typically including imaging and possibly endoscopy.

When Tests Are Normal

Normal blood tests rule out many serious causes but don’t mean nothing is wrong. Consider:

• Irritable bowel syndrome (IBS): A functional GI disorder diagnosed clinically when structural and inflammatory causes are ruled out. Blood tests are normal by definition. IBS is common, affecting 10-15% of adults, and bloating is a cardinal symptom. Management includes dietary modification (low-FODMAP diet), stress reduction, and sometimes medications.
• Food intolerances: Lactose, fructose, and other carbohydrate intolerances cause bloating but aren’t detected by standard blood tests. Elimination diets or breath tests can identify these.
• SIBO: Requires breath testing, not blood tests, for diagnosis. If clinical suspicion is high, breath testing is warranted even with normal blood work.
• Eating habits: Eating too quickly, not chewing thoroughly, talking while eating, or consuming carbonated beverages increases swallowed air. Large meals stretch the stomach and slow emptying.
• Gut-brain connection: Stress, anxiety, and depression can significantly affect gut function and perception. The gut-brain axis is bidirectional — emotional stress affects the gut, and gut symptoms affect mood.
• Medication effects: Many medications can cause bloating, including certain pain relievers, antibiotics, and supplements.

Lifestyle Approaches

While investigating underlying causes, these evidence-based strategies can help manage bloating:

Eating habits:

• Eat slowly and chew thoroughly: Rapid eating increases swallowed air and reduces mechanical digestion, leaving more work for the gut. Aim for at least 20 minutes per meal, putting your fork down between bites.
• Don’t talk while chewing: Talking during meals increases air swallowing.
• Eat smaller, more frequent meals: Large meals stretch the stomach and slow emptying. Smaller portions may cause less bloating.
• Avoid carbonated beverages: The gas in carbonated drinks — whether soda, sparkling water, or beer — goes directly into your GI tract.
• Avoid drinking through straws: Straws increase air swallowing.
• Limit chewing gum and hard candy: Both increase swallowed air, and sugar-free varieties often contain sugar alcohols (sorbitol, mannitol, xylitol) that are notorious bloating culprits.

Dietary modifications:

• Keep a food and symptom diary: Track what you eat and your symptoms to identify personal trigger foods. Patterns often emerge that aren’t obvious otherwise.
• Consider a low-FODMAP diet: Under guidance from a dietitian, a low-FODMAP diet eliminates fermentable carbohydrates and can significantly reduce bloating in many people, especially those with IBS. The diet involves elimination, reintroduction, and personalization phases.
• Identify and limit trigger foods: Common bloating triggers include beans, lentils, onions, garlic, wheat, dairy, cruciferous vegetables (broccoli, cabbage, Brussels sprouts), artificial sweeteners, and high-fructose foods.
• Don’t automatically eliminate all fiber: While some fermentable fibers cause bloating, fiber is important for gut health. Find a level and type that works for you.

Physical activity and posture:

• Stay physically active: Exercise promotes gut motility and can help move gas through the intestines. Even a short walk after meals can help.
• Avoid lying down immediately after eating: Staying upright for 2-3 hours after meals helps digestion and gas movement.
• Practice good posture: Slouching compresses the abdomen and may worsen the sensation of bloating.

Mind-body approaches:

• Manage stress: The gut-brain connection is powerful — stress, anxiety, and emotional distress significantly affect gut function. Chronic stress can alter gut motility, increase visceral sensitivity, and worsen bloating. Stress reduction techniques, mindfulness, yoga, and cognitive behavioral therapy can all help gut symptoms.
• Address anxiety and depression: These conditions are bidirectionally linked with gut problems. Treating mood disorders often improves gut symptoms, and improving gut health can help mood.
• Get adequate sleep: Poor sleep affects gut function and increases sensitivity to gut sensations.

Other approaches:

• Probiotics: May help some people, though evidence is mixed and benefits are strain-specific. Consider a 4-6 week trial of a high-quality probiotic to assess your personal response.
• Peppermint oil: Enteric-coated peppermint oil capsules may help with bloating and IBS symptoms through smooth muscle relaxation.
• Simethicone: An over-the-counter anti-foaming agent that may help some people by making gas easier to pass, though evidence is limited.
• Digestive enzymes: May help if specific enzyme deficiencies exist (lactase for lactose intolerance, for example).
• Avoid tight clothing: Tight waistbands can worsen the sensation of bloating and may affect gut function.

The Bottom Line

Chronic bloating is more than just a nuisance — it affects quality of life, can limit what you’re willing to eat and wear, and may signal an underlying condition that deserves attention. While occasional bloating after large meals or certain foods is completely normal, persistent bloating that doesn’t respond to reasonable dietary changes warrants investigation.

Celiac disease is a particularly important cause of bloating to identify because it’s common (affecting 1% of the population), dramatically underdiagnosed (most people with celiac don’t know they have it), and treatment with a gluten-free diet is highly effective. Anyone with chronic bloating — especially with diarrhea, fatigue, anemia, or other suggestive symptoms — should have celiac testing. A simple blood test could be life-changing.

Thyroid dysfunction, particularly hypothyroidism, is another common and easily treated cause of bloating. Hypothyroidism slows everything, including gut motility, leading to bloating and constipation. A TSH test can identify this.

Small intestinal bacterial overgrowth (SIBO) is increasingly recognized as a cause of chronic bloating, especially in people with risk factors like low stomach acid, slow gut motility, or previous GI surgery. While breath testing is needed for definitive diagnosis, blood tests can identify predisposing conditions and nutritional consequences.

In women, persistent bloating that doesn’t fluctuate with meals or dietary changes should prompt consideration of ovarian pathology. Ovarian cancer often presents with vague symptoms including bloating — it’s important not to dismiss these symptoms.

Food intolerances — lactose, fructose, and other FODMAPs — are common causes of bloating that can be identified through elimination diets and managed with dietary modification. Many people find significant relief with a low-FODMAP diet.

Blood tests can help in multiple ways:

• Identify celiac disease with tTG-IgA testing
• Detect thyroid dysfunction with TSH
• Rule out inflammatory conditions with CRP and CBC
• Assess for liver disease with liver enzymes and albumin
• Identify nutritional deficiencies that suggest malabsorption
• In women over 40 with persistent symptoms, CA-125 may be considered (with appropriate clinical context)

If blood tests are normal, functional conditions like IBS and food intolerances become more likely. These are real conditions that cause real symptoms — they’re just not detected by blood tests. Management focuses on dietary modification (low-FODMAP diet, avoiding triggers), stress reduction, gut-directed therapies, and sometimes medications.

Don’t accept chronic bloating as “just how your body is” or something you have to live with. With proper evaluation, many causes of bloating are identifiable and treatable. Finding the underlying cause — rather than just avoiding more and more foods — can resolve symptoms that dietary restriction alone couldn’t address.

---

Key Takeaways

• Chronic bloating often has an identifiable, treatable cause — don’t accept it as normal
• Celiac disease is a common and dramatically underdiagnosed cause — testing with tTG-IgA is simple and can be transformative if positive; most people with celiac don’t know they have it
• Hypothyroidism slows gut motility causing bloating and constipation — a simple TSH test can identify this treatable condition
• SIBO causes bloating through bacterial fermentation in the small intestine — diagnosed with breath testing; blood tests identify predisposing conditions and consequences
• Food intolerances (lactose, fructose, FODMAPs) are common causes that respond well to targeted dietary modification
• In women, persistent bloating warrants consideration of ovarian pathology — ovarian cancer often presents with vague symptoms including bloating
• Liver disease and heart failure can cause abdominal distension through fluid accumulation (ascites)
• IBS is a diagnosis of exclusion when blood tests and structural evaluations are normal — it’s a real condition with real treatments
• The gut-brain connection is powerful — stress, anxiety, and emotions significantly affect gut function and perception
• Key blood tests include tTG-IgA for celiac, TSH for thyroid, and inflammatory markers — these identify or rule out important causes