Overview.
Chronic bloating is one of the most common GI complaints, reported by 10-30% of adults. While often attributed to diet or stress, persistent bloating can signal treatable conditions: celiac disease, H. pylori infection, small intestinal bacterial overgrowth (SIBO), lactose intolerance, or early inflammatory bowel disease. A targeted lab workup identifies or excludes these causes without the need for upfront endoscopy in most cases.
Bloating is the subjective sensation of abdominal fullness, pressure, or distension. It may or may not be accompanied by visible abdominal distension. Functional bloating (no organic cause) is common, but chronic bloating warrants investigation when it persists >4 weeks, is progressive, or is accompanied by alarm features.
Prevalence: 10-30% of adults report recurrent bloating. It is the most common functional GI symptom reported to GPs. Women report bloating roughly 2x more often than men. Approximately 50% of patients with chronic bloating have an identifiable cause on targeted investigation.
What to test.
First-line tests
- Complete Blood Count — Screens for anaemia (iron deficiency from celiac disease, GI blood loss, or malabsorption) and elevated white cells (infection or inflammation).
- tTG-IgA + Total IgA — Celiac disease causes chronic bloating in >60% of patients. tTG-IgA is the best single screening test. Total IgA must be checked to rule out IgA deficiency (causes false negative tTG-IgA).
- TSH — Hypothyroidism slows gut motility, causing constipation and bloating. Simple to screen and easy to treat.
- CMP (Liver & Metabolic Panel) — Elevated ALT/AST may indicate liver disease (MASLD). Electrolyte abnormalities and glucose screening. Albumin for nutritional status.
Second-line tests
- Fecal Calprotectin (stool test) — Distinguishes inflammatory bowel disease from functional bloating/IBS with high accuracy. Normal calprotectin (<50 μg/g) effectively rules out significant intestinal inflammation.
- H. pylori Stool Antigen — H. pylori causes upper GI bloating, dyspepsia, and early satiety. Stool antigen is more accurate than serology for active infection.
- CRP — Elevated CRP suggests an inflammatory cause. Normal CRP with normal calprotectin supports a functional (non-inflammatory) diagnosis.
- Ferritin — Unexplained iron deficiency with bloating raises suspicion for celiac disease, IBD, or occult GI blood loss.
Specialized tests
- Hydrogen/Methane Breath Test — Tests for SIBO (small intestinal bacterial overgrowth) and specific carbohydrate intolerances (lactose, fructose). Consider if first/second-line tests are normal and bloating persists.
- Fasting Insulin / HOMA-IR — Insulin resistance is associated with SIBO and altered gut motility. Consider if metabolic syndrome features are present.
Common causes.
- Celiac Disease — Chronic bloating with diarrhoea, iron deficiency, fatigue; may have no classic GI symptoms
- H. pylori Infection — Upper abdominal bloating, early satiety, epigastric burning, nausea
- Hypothyroidism — Bloating with constipation, fatigue, weight gain, cold intolerance
Diagnostic patterns.
- Positive tTG-IgA + iron deficiency + chronic bloating — likely Celiac disease. Next step: Gastroenterology referral for duodenal biopsy; begin gluten-free diet after confirmation
- Normal tTG-IgA + normal calprotectin + normal CRP + chronic bloating — likely Functional bloating / IBS. Next step: Dietary modification (low-FODMAP trial), consider SIBO breath test if persistent
- Elevated calprotectin (>250 μg/g) + chronic diarrhoea + bloating — likely Inflammatory bowel disease. Next step: Gastroenterology referral for colonoscopy
- Positive H. pylori stool antigen + upper abdominal bloating — likely H. pylori gastritis. Next step: Eradication therapy; test of cure 4+ weeks after treatment
- Elevated TSH + constipation-predominant bloating + fatigue — likely Hypothyroidism. Next step: Full thyroid panel; levothyroxine if confirmed
Lifestyle.
Non-medical causes
- Eating too quickly or swallowing air (aerophagia)
- High-FODMAP diet (fermentable carbohydrates)
- Carbonated beverages
- Artificial sweeteners (sorbitol, xylitol, erythritol)
- Inadequate fibre (or sudden fibre increase)
- Sedentary lifestyle (reduced gut motility)
- Stress and anxiety (gut-brain axis dysfunction)
- Menstrual cycle hormonal changes (progesterone slows motility)
Considerations
- Low-FODMAP elimination diet for 4-6 weeks as a diagnostic and therapeutic trial
- Regular physical activity improves gut motility and reduces bloating
- Eat slowly and chew thoroughly
- Limit carbonated drinks and sugar alcohols
- Consider a food diary to identify trigger foods
- Stress management — the gut-brain axis significantly affects GI motility and sensation
FAQs.
What blood tests should I ask for if I'm always bloated?
Start with: tTG-IgA + total IgA (celiac screen), CBC (anaemia), CMP (liver function), TSH (thyroid). If these are normal, add fecal calprotectin (stool test for inflammation) and H. pylori stool antigen. This panel covers the most common treatable causes.
Is bloating ever serious?
Usually not — functional bloating is the most common cause. But bloating with weight loss, rectal bleeding, new onset after age 50, family history of GI cancer, or progressive worsening warrants prompt medical evaluation to rule out malignancy, IBD, or other organic causes.
Should I try a low-FODMAP diet before getting tested?
It's reasonable to try dietary modification for mild, intermittent bloating. But if bloating is persistent (>4 weeks), associated with alarm features, or you have risk factors for celiac disease or IBD, get tested first. A gluten-free diet before celiac testing causes false negatives.
My bloating is worse before my period — is that normal?
Yes. Progesterone rises in the luteal phase and slows gut motility, causing premenstrual bloating and constipation in many women. If it's mild and cyclical, it's typically hormonal. If severe or persistent throughout the cycle, investigate further.