What is IBS (irritable bowel syndrome)?

IBS is a long-lasting condition in which the gut and the brain-gut signaling that controls it work abnormally, causing recurring belly pain linked to bowel movements and changes in stool: diarrhea, constipation or both. The bowel looks normal on tests, and IBS does not damage the intestine or lead to cancer. It is common, affecting roughly 4% to 12% of adults depending on how it is defined, and is more common in women and in people under 50.

What are the symptoms of IBS?

The core symptom is belly pain that is related to bowel movements, often easing or changing after going, together with a change in how often you go or what the stool looks like. Many people also have bloating, a feeling that the bowel has not fully emptied, and whitish mucus in the stool. Symptoms often come and go over years, and women with IBS often have more symptoms during their periods.

How do you test for irritable bowel syndrome?

There is no single test that shows IBS. A clinician diagnoses it from the symptom pattern (the Rome IV criteria) plus a history and exam, and uses a few targeted tests to rule out look-alikes: a blood count for anemia, celiac antibodies (tTG-IgA with total IgA), and, when diarrhea is a feature, CRP and fecal calprotectin or lactoferrin to look for inflammatory bowel disease. A colonoscopy is reserved for people with warning signs or who are due for colon cancer screening.

IBS vs IBD: how do the symptoms differ?

Both can cause belly pain and diarrhea, which is why they get confused. Inflammatory bowel disease (Crohn's disease and ulcerative colitis) inflames and damages the bowel, so it is more likely to bring blood in the stool, weight loss, fever, night-time diarrhea and anemia, and it raises fecal calprotectin and CRP. IBS causes no inflammation or damage, so those markers stay normal. The tests, not the symptoms alone, separate them.

Is a fecal calprotectin of 100 high?

On a common scale (under 50 µg/g normal, 50 to 120 borderline, above 120 abnormal), a calprotectin of 100 µg/g is borderline. It may reflect mild inflammation, or a medicine such as an NSAID painkiller, aspirin or an acid-reducing proton pump inhibitor. Labs often suggest repeating a borderline result in 4 to 6 weeks; your clinician reads it with your symptoms and any red flags.

What is the best treatment for IBS?

There is no single best treatment; it depends on the main symptom and subtype. Guideline-backed first steps include soluble fiber such as psyllium, regular exercise, a limited trial of the low FODMAP diet with a dietitian, and peppermint oil for pain. Gut-directed psychological therapies, such as cognitive behavioral therapy and gut-directed hypnotherapy, are a guideline-suggested option. Prescription medicines for IBS with constipation or diarrhea, and low-dose tricyclic antidepressants for pain, are options a clinician may discuss.

Does the low FODMAP diet work for IBS?

The ACG recommends a limited trial of a low FODMAP diet to improve overall IBS symptoms, though it rates the quality of evidence as very low. FODMAPs are fermentable carbohydrates found in foods such as wheat, onions, some fruits and dairy. The diet is done in three steps, with a short strict phase of 2 to 6 weeks, a reintroduction phase to find personal triggers, and a longer-term personalized diet, ideally guided by a dietitian.

Do probiotics help IBS?

The evidence is weak and mixed. The ACG suggests against probiotics for overall IBS symptoms, and the AGA recommends their use for IBS only in the context of a clinical trial, because studies used many different strains and gave inconsistent results. Some people still try them; it is a reasonable question to discuss with your clinician, including the cost.

Can IBS turn into something more serious?

No. NIDDK states that IBS can be painful but does not lead to other health problems or damage the digestive tract. What matters is making sure the diagnosis is right: new warning signs such as blood in the stool, weight loss, anemia or night-time symptoms are a reason to be re-checked rather than a sign that IBS has changed.

IBS (irritable bowel syndrome): symptoms

Quick answer

Irritable bowel syndrome (IBS) is a common, long-lasting disorder of gut-brain interaction, meaning the gut and the nerves that control it work abnormally while the bowel itself looks healthy; it causes recurring belly pain linked to bowel movements, with diarrhea, constipation or both. ¹⁴ It is diagnosed from the Rome IV criteria, belly pain on at least 1 day a week over the last 3 months tied to two of three bowel changes, rather than from a test result. ³ The ACG recommends a positive diagnosis from that pattern instead of testing everything first, with a few targeted labs, such as celiac antibodies and, when diarrhea is present, fecal calprotectin (a stool marker of gut inflammation) and C-reactive protein (CRP), to rule out celiac disease and inflammatory bowel disease; red-flag features, not normal results, decide who needs a colonoscopy. ¹²

The distinctions

01
IBS is diagnosed by its pattern, not by everything coming back normal
The ACG suggests a positive diagnostic strategy: when the Rome IV symptom pattern is present and there are no warning signs, IBS can be diagnosed directly, with a few targeted tests, rather than after ruling out every possible disease. Normal results do not prove IBS on their own, and an abnormal result does not fit IBS; they answer different questions.
02
The tests are there to rule out look-alikes
Celiac antibodies, a blood count, CRP and fecal calprotectin look for celiac disease, anemia and inflammatory bowel disease, the conditions that most often mimic IBS. IBS does not cause inflammation or damage the intestine, so a high calprotectin or a low hemoglobin points away from IBS and toward further tests.
03
Red flags decide colonoscopy, not symptom severity
Severe IBS pain alone is not a reason for colonoscopy in a younger adult. Blood in the stool, weight loss, anemia, symptoms waking you at night, fever, a family history of colon cancer or inflammatory bowel disease, or new symptoms later in life are what move someone toward a scope.

Irritable bowel syndrome (IBS) is a common, long-term condition that causes repeated belly pain tied to bowel movements, along with diarrhea, constipation or both. ⁴⁵ It is now classed as a disorder of gut-brain interaction: the bowel looks normal on tests, but the way it moves and the way its nerves sense pain are out of tune. ¹⁵ IBS can be painful and disruptive, but it does not damage the intestine or lead to other diseases. ⁵ It is diagnosed from a symptom pattern called the Rome IV criteria, backed by a few targeted tests that rule out celiac disease and inflammatory bowel disease. ¹³ What to do next: track your symptoms for a few weeks (pain days, stool type, triggers, anything that wakes you at night) and bring that record to your clinician, along with any warning signs listed below.

What changes the way you see an IBS diagnosis

01Under the stricter Rome IV criteria, about 4.1% of adults in an online survey of 33 countries had IBS; under the older Rome III criteria the figure was 10.1%. ¹⁰
02A normal colonoscopy is not required to diagnose IBS in an adult under 45 without warning signs; the ACG recommends against routine colonoscopy in that group. ²
03For IBS with diarrhea, a fecal calprotectin under 50 µg/g makes active bowel inflammation unlikely on common lab scales. ¹²
04The ACG recommends against routine stool tests for infections and against food allergy or sensitivity testing unless symptoms clearly point to a food allergy. ²
05Treatment is matched to the main symptom: soluble fiber, low FODMAP, peppermint oil, gut-directed therapy and prescription options each have different strengths of evidence. ²

Symptoms of IBS

IBS symptoms usually come and go over months or years, often flaring with stress, certain foods or the menstrual cycle. The left column lists the typical pattern; the right column lists features that do not fit IBS and need a clinician's look. Associations only: these lists cannot diagnose IBS or rule anything out. ⁵⁶

Typical of IBS

Belly pain or cramping that is related to bowel movements
Diarrhea, constipation, or swings between the two
Bloating and a swollen-feeling belly
A feeling that the bowel has not fully emptied
Whitish mucus in the stool
Worse symptoms around periods

Do not fit IBS: get checked

Blood in the stool, or black, tarry stools
Unintentional weight loss
Diarrhea or pain that wakes you from sleep
Fever, or anemia on a blood test
New symptoms starting later in life
A family history of colon cancer, inflammatory bowel disease or celiac disease

Get care the same day Seek same-day care for heavy or ongoing rectal bleeding, black or tarry stools, severe belly pain that does not ease, a swollen hard belly with vomiting, fever with bloody diarrhea, or signs of dehydration such as very little urine, dizziness or confusion. These are not IBS symptoms and need prompt assessment.

Symptom pattern from NIDDK and warning signs from NIDDK and the ACG 2021 guideline ²⁵⁶. Associations only, never a way to diagnose yourself.

What is IBS, and who gets it?

IBS is defined by symptoms, not by a visible abnormality. NIDDK describes it as "a group of symptoms that occur together, including repeated pain in your abdomen" and changes in bowel movements. ⁴ The British Society of Gastroenterology reclassified it in 2021 as a disorder of gut-brain interaction rather than a functional gastrointestinal disorder, reflecting research on how the gut, its nerves and the brain signal to each other. ⁹

4.1%Adults meeting the Rome IV criteria for IBS in the Rome Foundation's 33-country online survey1.5% in household interviews; older, looser criteria gave about 10%. Sperber et al., Gastroenterology 2021 ¹⁰

How common IBS is depends on the definition. NIDDK cites studies suggesting about 12% of people in the United States have IBS, using older, broader criteria. ⁴ Women are up to twice as likely as men to develop it, and people under 50 more likely than those over 50. ⁴ People with IBS often have other conditions too: chronic pain conditions such as fibromyalgia, reflux or indigestion, and anxiety or depression. ⁴

No single cause has been found, and the mix differs between people. NIDDK lists problems with gut-brain interaction that change how the gut moves and senses pain, stressful or difficult early life events, anxiety and depression, bacterial infections of the digestive tract, small intestinal bacterial overgrowth (SIBO), food intolerances or sensitivities, and genes. ⁵ An IBS that begins after a bout of food poisoning or gastroenteritis is a recognized pattern, one reason a clinician will ask how symptoms started.

01Diagnosis and tests

How IBS is diagnosed: the Rome IV criteria

Clinicians diagnose IBS from the Rome IV criteria, published by the Rome Foundation. The core requirement is quoted here word for word, because each part matters: "Recurrent abdominal pain on average at least 1 day/week in the last 3 months," associated with two or more of three features. ³

Rome IV requirement	What it means in plain words
Recurrent belly pain, on average at least 1 day a week in the last 3 months ³	Bloating or discomfort alone is not enough; pain is required
Pain related to defecation ³	The pain changes, often eases, around bowel movements
Pain linked to a change in stool frequency ³	Going more or less often when the pain is present
Pain linked to a change in stool form ³	Looser or harder stools when the pain is present
Two or more of the three features above ³	One link to bowel habits is not enough
Criteria met for the last 3 months, with symptoms starting at least 6 months before diagnosis ³	A long-running pattern, not a recent change; NIDDK notes doctors may diagnose earlier in some cases ⁶

The ACG's first IBS guideline, published in 2021, makes this pattern the center of diagnosis. It states: "We suggest that a positive diagnostic strategy as compared to a diagnostic strategy of exclusion be used to improve time to initiating appropriate therapy." ¹ In practice, a clinician who sees the Rome IV pattern, finds no warning signs on history and exam, and gets normal results on a few targeted tests can diagnose IBS and start treatment, without a long chain of scans and scopes. NIDDK puts it plainly: "In most cases, doctors don't use tests to diagnose IBS." ⁶

The IBS subtypes: IBS-C, IBS-D and IBS-M

IBS is split into subtypes by the stool pattern on days when bowel movements are abnormal, and the ACG suggests that getting the subtype right improves treatment, because many therapies only help one subtype. ² NIDDK defines the subtypes by which stool types make up more than a quarter of abnormal bowel movements. ⁴ Some searches ask about "IBS-A," an older name for alternating IBS, which now falls under IBS-M.

Subtype	Stool pattern on abnormal days	Treatments aimed at it
IBS-C (constipation)	Hard or lumpy stools in more than a quarter of abnormal bowel movements ⁴	Soluble fiber, laxatives, prescription secretagogues ²⁷
IBS-D (diarrhea)	Loose or watery stools in more than a quarter of abnormal bowel movements ⁴	Loperamide, rifaximin, eluxadoline, alosetron ⁷¹⁴
IBS-M (mixed)	Both hard or lumpy and loose or watery stools, each in more than a quarter ⁴	Treatment follows whichever symptom is leading at the time
IBS-U (unclassified)	Meets IBS criteria but fits none of the patterns above	Treated by main symptom

The tests that rule out other causes

The few tests that matter in IBS are there to rule out the conditions that mimic it, chiefly celiac disease and inflammatory bowel disease (IBD), the umbrella term for Crohn's disease and ulcerative colitis. The ACG recommends celiac blood tests for people with IBS and diarrhea symptoms, and suggests checking fecal calprotectin (or fecal lactoferrin) and C-reactive protein in suspected IBS with diarrhea to rule out IBD. ² The British Society of Gastroenterology adds a complete blood count and CRP or ESR to the first-line primary care workup. ⁹

Marker	What it shows	Typical cutoff	First-line or add-on
Fecal calprotectin	Inflammation in the bowel wall; normal in IBS ¹¹	Under 50 µg/g normal; above 120 abnormal ¹²	First-line with diarrhea ²
Fecal lactoferrin	Another stool marker of bowel inflammation	Lab-specific; negative or positive	Alternative to calprotectin ²
CRP (C-reactive protein)	Inflammation anywhere in the body	Above the lab's range	First-line with diarrhea ²
ESR (sedimentation rate)	A slower, broader inflammation marker	Above the lab's range	Alternative to CRP ⁹
tTG-IgA with total IgA	Celiac disease; total IgA checks the test can be trusted	Lab-specific positive cutoff	First-line with diarrhea ²
Hemoglobin and MCV	Anemia, a warning sign that does not fit IBS ⁶	Below the lab's range	First-line ⁹
Ferritin	Iron stores; low iron points to blood loss or celiac disease	Below the lab's range	Add-on when anemia or low iron
TSH	Thyroid problems, which can also change bowel habits	Outside the lab's range	Not in the routine IBS workup in the ACG or BSG guidance; checked when other symptoms point to the thyroid ²⁹
FIT (fecal immunochemical test)	Hidden blood in the stool	Positive or negative	Colorectal screening; not an IBS test

Then read the results together. The inflammation markers guide explains CRP and ESR, and the CBC guide the blood count.

Pattern	What it usually means
Rome IV symptoms, normal blood count, CRP, celiac tests and calprotectin, no warning signs	Fits IBS; a positive diagnosis can be made ¹²
Calprotectin above 120 µg/g, or a raised CRP	Active inflammation; IBD, infection or another cause needs looking into, often by colonoscopy ¹¹¹²
Calprotectin 50 to 120 µg/g	Borderline; may be mild inflammation or a medicine effect; often repeated in 4 to 6 weeks ¹²
Positive tTG-IgA	Celiac disease is likely; see the celiac disease page
Low hemoglobin or ferritin	Anemia or iron deficiency; a warning sign that needs a cause found ⁶
Abnormal TSH	A thyroid problem may be contributing to bowel changes; the clinician looks into it before settling on IBS
Positive FIT	Hidden blood; colonoscopy is the usual next step

Tests the ACG recommends against in typical IBS

Routine stool testing for infections (enteric pathogens) in everyone with IBS. ²
Routine colonoscopy in people with IBS symptoms younger than 45 without warning signs; age-appropriate colon cancer screening still applies. ²
Food allergy and food sensitivity tests, unless there are reproducible symptoms that suggest a true food allergy. ²
The British Society of Gastroenterology also advises against routine testing for small intestinal bacterial overgrowth or pancreatic insufficiency when symptoms are typical of IBS. ⁹

Consumer gut microbiome tests are not part of the guideline workup for IBS, and no microbiome pattern diagnoses it. If you already have such a report, the gut microbiome test guide explains what the diversity scores and bacterial names can and cannot tell you.

Fecal calprotectin under 50, 50 to 120, or over 120: what the number means

Fecal calprotectin is a protein released by white blood cells in an inflamed bowel, measured in a small stool sample. MedlinePlus explains that its main use is telling IBD apart from IBS, because "only IBD involves inflammation." ¹¹ Cutoffs vary by lab, so check the range on your report; the bands below come from one hospital laboratory handbook. ¹²

Where an example fecal calprotectin of 80 µg/g fallsµg/g

80 µg/gborderline · example value; same as 80 mcg/g or mg/kg

Normal0–50Borderline50–120Abnormal120–300

A calprotectin of 80 µg/g is borderline: it may reflect mild inflammation, or a medicine such as an NSAID, aspirin or a proton pump inhibitor. A repeat in 4 to 6 weeks is a common next step, sooner if warning signs are present; your clinician decides.

Illustrative example. Bands from the University of Iowa pathology handbook: under 50.0 normal, 50.0 to 120 borderline, above 120 suggestive of active inflammation, with repeat testing in 4 to 6 weeks suggested for borderline results. ¹² Your lab's printed range applies to your result.

Calprotectin under 50 µg/g: not suggestive of active bowel inflammation, which fits IBS when the symptom pattern matches. ¹² MedlinePlus notes false negatives can occur, mostly in children. ¹¹
Calprotectin 50 to 120 µg/g: borderline. NSAID painkillers, aspirin and proton pump inhibitors can push results into this band. ¹²
Calprotectin above 120 µg/g: suggests active inflammation. IBD is one cause; infections such as C. diff, celiac disease and colorectal cancer are others, so a clinician usually arranges further tests. ¹¹¹²
Calprotectin in the hundreds or higher: very high levels are mainly linked to IBD and some gut infections. ¹¹

IBS vs IBD and other look-alikes

IBS or IBD: inflammation markers tell them apart

IBSGut-brain disorder, no inflammation

Irritable bowel syndrome

What happens in the bowelAltered movement and pain signaling; the bowel looks normal

Fecal calprotectinNormal (under 50 µg/g on common scales)

CRP and blood countNormal

Blood in stool, weight loss, feverNot features of IBS

ColonoscopyNormal; not routine under 45 without warning signs

Long-term damageNone

IBD✓ Inflammatory disease that needs a specialist

Crohn's disease or ulcerative colitis

What happens in the bowelImmune inflammation that damages the bowel wall

Fecal calprotectinUsually raised, often well above 120 µg/g

CRP and blood countCRP often raised; anemia common

Blood in stool, weight loss, feverCommon

ColonoscopyShows inflammation and ulcers; biopsies confirm

Long-term damageYes, without treatment

MedlinePlus: calprotectin mainly helps distinguish IBD from IBS, because only IBD involves inflammation ¹¹. The ACG suggests calprotectin or lactoferrin plus CRP to rule out IBD in suspected IBS with diarrhea, and recommends against routine colonoscopy under 45 without warning signs ². The IBD card is marked because a positive inflammation result moves the workup toward it.

Look-alike	What overlaps with IBS	The test that tells them apart
Celiac disease	Bloating, diarrhea, pain	tTG-IgA with total IgA, while eating gluten ²
Inflammatory bowel disease	Pain, diarrhea	Fecal calprotectin, CRP, colonoscopy ²¹¹
Microscopic colitis	Watery diarrhea, often in women over 50	Colonoscopy with biopsies, even if the bowel looks normal ⁹
Bile acid diarrhea	Diarrhea, often at night or after gallbladder removal	Specialist bile acid testing ⁹
Lactose intolerance or SIBO	Bloating, gas, loose stools	Hydrogen breath test ⁶
Hyperthyroidism	Frequent loose stools, weight loss	TSH and free T4, when other thyroid symptoms are present; not part of the routine IBS workup
Hypothyroidism	Constipation, tiredness	TSH, when other thyroid symptoms are present; not part of the routine IBS workup
Iron deficiency and anemia	Tiredness alongside gut symptoms	Blood count and ferritin; anemia is a warning sign ⁶
Colorectal cancer	Change in bowel habit	FIT, colonoscopy; age and red flags guide it ²

02Treatment

IBS treatment: what helps, and how strong the evidence is

IBS treatment is matched to the main symptom and subtype, and most people try a few approaches before finding what works. The ACG guideline graded 16 treatment questions using GRADE, a standard system that rates both how firmly a guideline recommends something and how good the evidence is. ¹ The grades below translate those ratings into Strong, Moderate, Limited or Not supported.

Approach	What the evidence shows	Strength	Cautions
Soluble fiber (psyllium, also called ispaghula)	ACG suggests soluble, but not insoluble, fiber for overall symptoms (moderate-quality evidence); BSG lists it first-line with exercise ²⁹	Moderate	Increase gradually to limit gas; insoluble wheat bran is not recommended ⁹
Regular exercise	First-line in the BSG guideline; NIDDK lists physical activity, stress management and sleep ⁷⁹	Limited	Few side effects
Low FODMAP diet, limited trial	ACG recommends a limited trial for overall symptoms; evidence quality rated very low ²	Limited	Best with a dietitian; strict phase is short; not a lifelong diet ¹³
Peppermint oil	ACG suggests it for overall symptoms (low-quality evidence); NIDDK lists coated capsules for pain ²⁷	Limited	Can worsen heartburn; ask about interactions
Gut-directed psychotherapy (CBT, gut-directed hypnotherapy)	ACG suggests it for overall symptoms; evidence quality rated very low ¹²	Limited	Access varies; works alongside other treatments
Tricyclic antidepressants, low dose (prescription)	ACG recommends them for overall symptoms (strong, moderate-quality evidence); they act on gut pain nerves ²	Strong	Prescription; side effects such as dry mouth and constipation; the clinician decides
Prescription options for IBS-C (linaclotide, plecanatide, lubiprostone)	ACG recommends guanylate cyclase and chloride channel activators ¹²	Strong	Diarrhea is the common side effect; the clinician decides. Tegaserod, also in the 2021 ACG guideline, was withdrawn from the US market in 2022
Prescription options for IBS-D (rifaximin, eluxadoline, alosetron)	ACG recommends rifaximin; the AGA gives conditional recommendations for all three ¹¹⁴	Moderate	Alosetron is restricted to women with severe symptoms ²⁷
Loperamide for diarrhea	AGA conditional recommendation, very low certainty; BSG lists it ⁹¹⁴	Limited	Helps stool frequency more than pain
Antispasmodics	ACG recommends against them for overall symptoms; AGA conditional for, low certainty ²¹⁴	Limited	May help cramping for some
Probiotics	ACG suggests against for overall symptoms; AGA: only in clinical trials, a knowledge gap ²⁸	Not supported	Cost; products vary widely
SSRIs (a type of antidepressant)	AGA conditional recommendation against for IBS-D, low certainty ¹⁴	Not supported	May still be used for anxiety or depression
Fecal transplant	ACG recommends against for IBS ²	Not supported	Not an IBS treatment outside research

Prescription medicines in the table are named so you recognize them; whether any fits you, and which, is a decision for your clinician, who weighs your subtype, other conditions and side effects. Do not start, stop or combine prescription medicines without them.

The low FODMAP diet for IBS in three steps

FODMAPs are fermentable oligosaccharides, disaccharides, monosaccharides and polyols: short-chain carbohydrates that some people absorb poorly, so gut bacteria ferment them into gas and they draw water into the bowel. ¹ They are found in foods such as wheat, onions, garlic, beans, some fruits and milk. The diet is a short test, not a permanent way of eating, and Monash University, which developed it, advises doing it with a dietitian. ¹³

1Step 1: low FODMAPSwap high-FODMAP foods for low-FODMAP ones for 2 to 6 weeks, under a dietitian's guidance. If symptoms do not improve, the diet is unlikely to be the answer. ¹³
2Step 2: reintroductionBring FODMAP groups back one at a time to see which trigger symptoms; this takes most people around 6 to 8 weeks. ¹³
3Step 3: personalizationSettle on a longer-term diet that includes everything you tolerate and limits only your own triggers. ¹³

A strict low FODMAP diet cuts out many high-fiber foods, so staying in step 1 for months risks a narrow diet. People with a history of eating disorders, or who are already losing weight, should raise that with their clinician before starting any restrictive diet. Cutting out wheat before celiac testing can also make celiac blood tests falsely negative, so celiac testing comes first, as the celiac disease page explains.

Probiotics and magnesium: where the supplement guides fit

Probiotics are the supplement most often tried for IBS, and the evidence is the weakest. The AGA states: "In symptomatic children and adults with irritable bowel syndrome, we recommend the use of probiotics only in the context of a clinical trial," because the trials used many different strains and gave inconsistent results. ⁸ The probiotics guide covers which uses do have evidence and how products differ. Magnesium also comes up in searches about IBS with constipation, because some over-the-counter laxatives contain magnesium. NIDDK lists laxatives in general among the options for IBS-C ⁷, but none of the IBS guidelines cited on this page grades magnesium as an IBS treatment, and the ACG suggests against another common laxative, polyethylene glycol, for overall IBS-C symptoms. ² The magnesium guide covers the forms and the main caution: people with kidney disease can build up magnesium to unsafe levels, so any magnesium product is a conversation with a clinician first.

We suggest that a positive diagnostic strategy as compared to a diagnostic strategy of exclusion be used to improve time to initiating appropriate therapy.

Lacy and colleagues, ACG clinical guideline: management of irritable bowel syndrome, 2021

Monitoring and when to retest

Once IBS is diagnosed, routine repeat testing is not needed while the pattern stays the same, because IBS does not damage the bowel. ⁵ Retesting has a purpose when something changes. See why a trend beats a single reading for how to read a repeat result.

What gets rechecked	When	Why
Fecal calprotectin	In 4 to 6 weeks after a borderline result ¹²	Separates a passing rise from ongoing inflammation
Hemoglobin and ferritin	If tiredness, paleness or new symptoms appear	Anemia is a warning sign that does not fit IBS ⁶
tTG-IgA	If diarrhea symptoms persist and celiac testing was never done, or was done while gluten-free	Celiac disease is a common look-alike ²
CRP	With new diarrhea, fever or night symptoms	Points to inflammation rather than IBS ²
Colorectal cancer screening (FIT or colonoscopy)	From the standard screening age, or earlier with red flags	IBS does not remove the need for routine screening ²⁹
Symptom diary	Before and after each treatment trial	Shows whether a change helped; most trials need several weeks

Questions to ask your clinician

Do my symptoms meet the Rome IV criteria, and which subtype am I: IBS-C, IBS-D or IBS-M?
Have celiac disease and inflammatory bowel disease been ruled out? Was my total IgA checked with the celiac test?
Should we check fecal calprotectin and CRP, given my diarrhea?
Do any of my symptoms count as warning signs that mean I need a colonoscopy?
Is a low FODMAP trial a good fit, and can you refer me to a dietitian?
Would soluble fiber, peppermint oil or gut-directed therapy suit my main symptom?
Which prescription options exist for my subtype, and what are their side effects?
When should I be screened for colorectal cancer?

For more depth, the gut hub gathers the digestive markers, the inflammation hub covers CRP and related tests, and the celiac disease page covers the antibody test in full.

This page is general education, not medical advice or a diagnosis. The clinician who knows your history and full results is the right person to interpret your tests and decide on treatment with you.

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Markers to check

FCFecal Calprotectin tTG-IgATissue Transglutaminase IgA IgAImmunoglobulin A CPC-Reactive Protein HEMHemoglobin FERFerritin FLFecal Lactoferrin ESRErythrocyte Sedimentation Rate TSHThyroid Stimulating Hormone FITFecal Occult Blood Test MCVMean Corpuscular Volume

What can help

Educational only: LifeFrom explains lab results and does not diagnose or treat IBS. Heavy rectal bleeding, black stools, severe belly pain or signs of dehydration need same-day care, and weight loss, anemia, fever or night-time symptoms need a prompt appointment. Find the cause with a clinician before starting anything, including supplements or a restrictive diet.

Probiotics Magnesium

Citations

Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.

IBS (irritable bowel syndrome): symptoms, the tests that rule out other causes, and what helps