The Root Cause Bloating Guide: Tests, Patterns, and What to Ask Your Doctor
How to Use This Guide
This guide is a companion to the Root Cause Rx episode: Why Am I Always Bloated?
By the end of that episode, at least one root cause pattern probably resonated with you. Use this guide to go deeper on that specific pattern — what it looks like, how to test for it, and exactly what to ask your doctor or functional medicine practitioner.
Don't try to investigate everything at once. Identify your pattern. Start there.
PATTERN 1 — Low Stomach Acid
What it feels like: You feel overly full after normal sized meals. Protein feels especially heavy and hard to digest. You burp repeatedly after eating. Bloating starts early, within thirty minutes of a meal.
Why it happens: Stomach acid is the ignition of your entire digestive system. When it's low, food sits longer than it should, fermentation starts earlier than it should, and the rest of your digestive cascade never fully activates.
Common drivers: Chronic stress, age, long term use of antacids or proton pump inhibitors, H. pylori infection, nutrient deficiencies particularly zinc and B vitamins.
What to test:
Heidelberg pH capsule test — the gold standard for measuring stomach acid directly. Not widely available through conventional medicine but offered by many functional medicine practitioners.
Betaine HCl challenge — a functional self-test. Work with a practitioner to do this properly.
H. pylori breath test or stool antigen test — H. pylori bacteria directly suppresses stomach acid production and is extremely common. This should be ruled out first.
Serum pepsinogen I and II — can indicate stomach acid insufficiency and gastric lining health.
Full nutrient panel including zinc and B12 — both are required for adequate acid production and are commonly depleted.
What to ask your doctor:"I'm experiencing symptoms consistent with low stomach acid — early fullness, heavy digestion after protein, frequent burping. Can we rule out H. pylori and assess my gastric acid function? I'd also like to check zinc and B12 levels."
One thing to do today: Slow down at meals. Sit down, remove distractions, and give your nervous system time to activate digestion before food arrives. Stomach acid production is directly tied to parasympathetic state.
PATTERN 2 — Sluggish Bile Flow
What it feels like: Fatty foods make you feel worse, heavy, uncomfortable, mildly nauseated, about forty five minutes to an hour after eating. You feel pressure or fullness under your right rib cage. You may have been told to avoid fat without being told why.
Why it happens: Bile is produced by the liver, stored in the gallbladder, and released when you eat fat. When bile flow is sluggish, fat doesn't get broken down properly, it sits longer, and because bile is also a motility signal, your overall digestive movement slows down too.
Common drivers: Low fat diet, chronic dehydration, hormonal shifts particularly in women, gut microbiome imbalance, sluggish liver function, previous gallbladder removal.
What to test:
HIDA scan with ejection fraction — measures how well the gallbladder contracts and releases bile. This is the most direct assessment of gallbladder function. Standard ultrasound misses functional problems, make sure to ask specifically for ejection fraction.
Liver function panel — ALT, AST, GGT, alkaline phosphatase. GGT is particularly sensitive to bile flow issues.
Comprehensive stool analysis — can reveal fat malabsorption and bile acid insufficiency.
Organic acids test — can identify impaired fat metabolism and liver detoxification capacity.
Hormonal panel — particularly relevant for women experiencing cyclical digestive symptoms.
What to ask your doctor:"I consistently feel worse after fatty meals with pressure under my right rib cage. I'd like to assess gallbladder function with a HIDA scan including ejection fraction, not just an ultrasound. I'd also like to look at liver function including GGT."
One thing to do today: Stop avoiding fat. Your gallbladder needs fat in your diet to get the signal to contract and release bile. Add small amounts of healthy fat back into every meal and support bile production with bitter foods, arugula, dandelion greens, lemon water before meals.
PATTERN 3 — Small Intestinal Bacterial Overgrowth (SIBO)
What it feels like: You bloat within thirty to ninety minutes of eating, especially after fiber, onions, garlic, legumes, and carbohydrates. Healthy foods make you feel worse. You may have been told you have IBS. Probiotics may have made your symptoms worse rather than better.
Why it happens: Bacteria that belong in the large intestine have migrated upstream into the small intestine, where they ferment food too early, producing gas in a space not designed to handle it. The foods that feed these bacteria most, fiber and fermentable carbohydrates, become your worst triggers.
Common drivers: Sluggish gut motility, low stomach acid, previous gut infections or food poisoning, antibiotic use, chronic stress, structural issues in the gut.
What to test:
Lactulose or glucose breath test — the standard SIBO test. Measures hydrogen and methane gas produced by bacteria in the small intestine after consuming a sugar solution. Non-invasive, can often be done at home with a kit. Make sure the test measures both hydrogen and methane — methane dominant SIBO is often missed when only hydrogen is measured.
Trio-Smart breath test — the most comprehensive breath test available, measuring hydrogen, methane, and hydrogen sulfide. Hydrogen sulfide SIBO is frequently missed on standard tests.
Comprehensive stool analysis — assesses bacterial balance in the large intestine and identifies dysbiosis patterns.
Organic acids test — can identify bacterial and fungal metabolites that suggest overgrowth.
What to ask your doctor:"My symptoms fit a SIBO pattern, I bloat rapidly after fiber and fermentable foods and I feel worse eating healthy. I'd like to do a lactulose breath test measuring both hydrogen and methane. Can we also discuss what might be driving the overgrowth so we're not just treating it without addressing the root cause?"
One thing to do today: Stop snacking. Create true gaps between meals — three to four hours minimum. Your Migrating Motor Complex runs between meals and clears bacteria from the small intestine. Constant eating prevents it from doing its job.
PATTERN 4 — Sluggish Gut Motility
What it feels like: Food feels like it parks and doesn't move. Bowel movements are infrequent or feel incomplete. Your bloating builds meal by meal across the day, each meal adding to what the previous one left behind. By evening you're carrying the compounded weight of everything you ate since morning.
Why it happens: Your gut has a built-in cleaning cycle called the Migrating Motor Complex that runs between meals, moves food forward, and clears bacteria. When this slows down, food lingers, bacteria linger, fermentation increases, and the conditions for SIBO develop.
Common drivers: Chronic stress, hypothyroidism, certain medications particularly opioids and some sleep aids, previous gut infections that damaged the nerves controlling motility, eating too frequently, magnesium deficiency.
What to test:
Whole gut transit time study — measures how long it takes food to move through your entire digestive tract. A simple at-home version involves eating a known amount of sesame seeds or corn and tracking when they appear in stool.
Sitz marker study or SmartPill motility capsule — more precise clinical assessments of where transit is slowing down.
Full thyroid panel — TSH alone is not sufficient. Request free T3, free T4, reverse T3, and thyroid antibodies. Hypothyroidism is one of the most common and most missed drivers of sluggish motility and is frequently undertreated when only TSH is measured.
Serum magnesium — standard serum magnesium misses intracellular deficiency. Ask for RBC magnesium for a more accurate picture.
SIBO breath test — given the direct connection between motility and bacterial overgrowth, these two patterns should be investigated together.
What to ask your doctor:"I have symptoms of sluggish gut motility, food feels like it sits, bloating builds across the day, bowel movements feel incomplete. I'd like a full thyroid panel including free T3 and reverse T3, an RBC magnesium level, and I'd like to discuss motility testing options."
One thing to do today: Add magnesium glycinate or magnesium citrate before bed. Magnesium supports smooth muscle function in the gut and is one of the most commonly deficient nutrients in people with sluggish motility. Start with a low dose and adjust based on response.
PATTERN 5 — Nervous System Dysregulation
What it feels like: Your symptoms are noticeably worse on stressful days. You eat quickly and distracted. Mondays are harder than Sundays. Travel weeks are always your worst gut weeks. You feel like you never fully relax, and your gut never fully settles.
Why it happens: Digestion is a parasympathetic function. Your body can only digest well when it feels safe. Chronic sympathetic activation, the low grade stress most of us carry, suppresses stomach acid, slows motility, alters the microbiome, and increases gut sensitivity over time.
Common drivers: Chronic psychological stress, poor sleep, blood sugar instability, unresolved trauma, over-exercise, under-recovery, high caffeine intake, screens and overstimulation.
What to test:
DUTCH Complete test — measures cortisol and cortisone at multiple points across the day, giving you a full picture of your HPA axis rhythm. A single cortisol blood draw only captures one moment and misses the full pattern. The DUTCH also measures sex hormones, melatonin metabolites, and key nutrient markers.
Four point salivary cortisol test — a more accessible alternative to the DUTCH that measures cortisol rhythm across morning, midday, afternoon, and evening.
Heart rate variability — not a lab test but a measurable biomarker of nervous system state. Trackable through wearables like Oura Ring, Garmin, or Apple Watch. Low HRV consistently correlates with digestive dysfunction and sympathetic dominance.
Organic acids test — can identify neurotransmitter metabolites that reflect chronic stress burden on the nervous system.
What to ask your doctor:"I believe chronic stress is affecting my digestive function. I'd like to assess my cortisol rhythm with a DUTCH test or four point salivary cortisol rather than a single blood draw. I'd also like to discuss HPA axis support as part of my treatment plan."
One thing to do today: Before your next meal, put the phone down, sit down, and take three slow breaths. Give your body sixty seconds to shift into parasympathetic mode before food arrives. This is not a permanent fix. But it is real physiology and it matters more than most people think.
PATTERN 6 — Blood Sugar Instability
What it feels like: You experience energy crashes one to two hours after meals. You get cravings for sugar or caffeine in the afternoon. You feel irritable when you haven't eaten. Your bloating tends to be worst later in the day. You may feel best when you skip breakfast but crash hard by mid morning.
Why it happens: Blood sugar spikes and crashes trigger cortisol responses. Each cortisol surge activates the sympathetic nervous system, which downregulates digestion, slowing motility, reducing stomach acid, and increasing gut sensitivity. For people with frequent blood sugar instability, this is happening multiple times a day.
Common drivers: High carbohydrate meals without adequate protein and fat, skipping meals, chronic stress, poor sleep, insulin resistance, sedentary lifestyle.
What to test:
Fasting glucose and fasting insulin together — fasting glucose alone misses early insulin resistance. Calculate HOMA-IR using both values. A HOMA-IR above 1.5 suggests developing insulin resistance even when fasting glucose appears normal.
Hemoglobin A1c — reflects average blood sugar over the past ninety days. Optimal functional range is below 5.4, lower than the conventional normal cutoff.
Continuous glucose monitor — two weeks of CGM data will show you exactly which meals spike and crash your blood sugar, when your worst fluctuations occur, and how your blood sugar responds to stress and sleep. More informative than any single lab value. Available without a prescription through companies like Levels or Nutrisense.
Fasting triglycerides and HDL ratio — an underused marker of metabolic health and insulin sensitivity.
What to ask your doctor:"I'd like to assess my blood sugar stability beyond just fasting glucose. Can we run fasting insulin alongside glucose so we can calculate HOMA-IR? I'd also like hemoglobin A1c and a lipid panel with triglycerides."
One thing to do today: Add protein to breakfast. Today. Eating protein within an hour of waking stabilizes your blood sugar curve for the entire day. Never eat carbohydrates alone — always anchor them with protein and fat. This single change reduces the cortisol spikes hitting your gut before lunch.
PATTERN 7 — Compromised Gut Lining
What it feels like: Everything seems to bother you. Your reactions feel random and unpredictable — you eat something fine on Tuesday and react to the same thing on Wednesday. The list of foods that bother you keeps growing. You have bloating plus discomfort — not just distension but actual aching or pain. You feel like your body has turned against you for no reason.
Why it happens: The gut lining is one cell thick and separates your gut contents from your bloodstream. When it becomes inflamed and compromised — through chronic stress, bacterial overgrowth, undigested food particles, medications, alcohol, or any combination of the above — it becomes hypersensitive. Normal digestion feels like an attack. Normal gas feels like pain.
Common drivers: Chronic stress, SIBO or dysbiosis, NSAIDs and alcohol, low stomach acid allowing undigested food particles to reach the lining, food sensitivities creating ongoing immune activation, nutrient deficiencies particularly zinc and vitamin D.
What to test:
Lactulose mannitol intestinal permeability test — directly measures how permeable your gut lining is by tracking how much of each sugar crosses into the bloodstream.
Zonulin — a protein that regulates tight junctions in the gut lining. Elevated zonulin in stool or blood indicates increased intestinal permeability.
Comprehensive stool analysis — the single most informative test for someone in the reactive everything phase. Assesses bacterial balance, inflammation markers including calprotectin and secretory IgA, digestive enzyme sufficiency, fungal overgrowth, and immune activation all in one test. GI-MAP and Genova GI Effects are two widely used options.
Serum zinc and vitamin D — both are critical for gut lining integrity and are commonly deficient in people with compromised barriers.
Food sensitivity panel — IgG food sensitivity testing is controversial but can be useful as a temporary roadmap when someone is reacting to many foods. Best used as a short term guide while addressing root causes rather than a permanent elimination list.
What to ask your doctor:"I'm in a phase where everything seems to bother me and my reactions are unpredictable. I'd like to assess gut lining integrity with a permeability test and a comprehensive stool analysis. I'd also like to check zinc and vitamin D levels."
One thing to do today: Remove the three biggest gut lining disruptors immediately, alcohol, ibuprofen and other NSAIDs, and chronic sleep deprivation. Then add one gut lining support nutrient, collagen powder in your morning coffee or bone broth daily. Simple. Consistent. Start there.
A Note on Working With a Practitioner
Most of the tests listed in this guide are not standard on a conventional medicine panel. Many require a functional medicine practitioner to order, interpret, and build a treatment plan around.
If you're ready to work with someone who thinks in root causes rather than symptom management, look for a practitioner certified through the Institute for Functional Medicine (IFM) or trained in functional and integrative medicine.
The goal is never to collect test results. The goal is to identify your specific pattern, understand the mechanism driving it, and address that mechanism directly.
That's Root Cause Medicine. And that's what actually moves the needle.
This guide is for educational purposes and is not intended as medical advice. Always work with a qualified healthcare provider before beginning any testing or treatment protocol.