Can Celiac Disease Be Misdiagnosed as IBS? Why Up to 83% of Cases Go Undetected

Celiac disease can absolutely be misdiagnosed as IBS, and it happens far more often than most patients or clinicians expect. An estimated 83% of the roughly 3 million Americans with celiac disease have not been correctly diagnosed. Many of them have been told they have irritable bowel syndrome. The reasons are systemic: celiac screening is not always included in the IBS workup, the condition presents atypically in most adults, and the growing popularity of the 'gluten sensitivity' label can inadvertently steer patients away from definitive testing. The consequences of this delay are not just years of unnecessary symptoms. They include preventable complications like osteoporosis, infertility, and increased lymphoma risk.

Why does celiac misdiagnosis happen so often?

The root of the problem is that IBS is a diagnosis of exclusion, but the exclusion process is often incomplete. The Rome IV criteria for IBS are symptom-based: recurrent abdominal pain associated with defecation, changes in stool frequency, or changes in stool form. Meeting these criteria does not require any specific blood work or imaging. Some clinicians assign the IBS label based on symptom patterns alone, without ordering the tests that would identify conditions like celiac disease.

A 2001 study by Green and colleagues in the Archives of Internal Medicine surveyed over 1,000 celiac patients and found that 32% had been previously diagnosed with IBS. The average time from symptom onset to celiac diagnosis was 11 years. Patients saw an average of 5 physicians before receiving the correct diagnosis. These numbers have improved somewhat as awareness has grown, but a 2014 study by Fuchs and colleagues still documented a mean diagnostic delay of 5 to 12 years across European countries, suggesting the problem is far from solved.

What does atypical celiac disease look like?

The textbook picture of celiac disease is a thin patient with chronic diarrhea, malabsorption, and failure to thrive. This classical presentation does exist, particularly in children, but it represents the minority of adult celiac diagnoses. Fasano and Catassi (2001) described the 'celiac iceberg' in which the visible tip (classical symptoms) accounts for a small fraction of total cases, while the larger submerged portion includes atypical, silent, and latent celiac disease.

Atypical celiac disease can present with constipation rather than diarrhea, normal or even elevated body weight, isolated iron deficiency anemia without obvious GI symptoms, unexplained liver enzyme elevations, neurological symptoms like peripheral neuropathy or ataxia, or reproductive problems including infertility and recurrent miscarriage. Because these presentations do not match the expected profile, celiac testing may not be ordered. A patient with constipation-predominant symptoms and normal weight is more likely to be diagnosed with IBS-C than to receive a tTG-IgA test.

What is seronegative celiac disease, and why does it complicate diagnosis?

Seronegative celiac disease refers to cases where the tTG-IgA blood test is negative but duodenal biopsy reveals villous atrophy consistent with celiac disease. Estimates suggest this accounts for 6 to 22% of celiac diagnoses, depending on the study population and how rigorously other causes of villous atrophy are excluded (Aziz et al., 2017). In these patients, the standard screening blood test provides false reassurance.

Seronegative celiac can occur for several reasons. Some patients have selective IgA deficiency, which renders all IgA-based tests unreliable. Others may have lower-grade mucosal damage that generates antibody levels below the test threshold. In some cases, patients have already reduced their gluten intake before testing, suppressing antibody production without being on a fully gluten-free diet. This is why total serum IgA should always be measured alongside tTG-IgA, and why clinical suspicion should not be abandoned solely on the basis of a negative blood test.

What are the consequences of delayed celiac diagnosis?

Delayed diagnosis of celiac disease is not just an inconvenience. It carries measurable health consequences that accumulate over time. A landmark study by Ventura and colleagues (1999) found that the prevalence of autoimmune conditions in celiac patients increased as a function of disease duration. Patients diagnosed before age 2 had an autoimmune disease prevalence of roughly 5%, while those diagnosed after age 20 had a prevalence of 34%. While this study has limitations and the causal direction is debated, it suggests that prolonged untreated celiac disease increases autoimmune risk.

The 'gluten sensitivity' trap: how a label can delay proper testing

The growing awareness of gluten-related symptoms has had an unintended consequence. Some patients who notice improvement after reducing gluten assume they are 'gluten sensitive' and adopt a gluten-free or gluten-reduced diet without ever being tested for celiac disease. Once gluten is removed, antibody levels drop and intestinal damage begins to heal, making subsequent testing unreliable. These patients may carry the label of non-celiac gluten sensitivity for years or decades when they actually have celiac disease.

The same problem can occur when clinicians suggest a trial gluten-free diet as a diagnostic or therapeutic strategy before ordering celiac serology. While well-intentioned, this approach can make definitive diagnosis impossible without a prolonged gluten challenge, which many patients are understandably reluctant to undergo after experiencing symptom improvement. The clinical guideline is clear: test first, then trial dietary changes. A single blood draw while the patient is still eating gluten is all it takes to start the process.

Who should be screened, and what should you ask your doctor?

If you have been diagnosed with IBS and have never been screened for celiac disease, the conversation with your doctor is straightforward. You are asking for a tTG-IgA blood test and a total serum IgA level. Both can be drawn at the same time, and results are typically available within a few days. The only prerequisite is that you must be eating gluten regularly when the blood is drawn.

If your doctor is reluctant to order celiac testing because your symptoms look like IBS, it is reasonable to explain that the American College of Gastroenterology recommends serological testing for celiac disease in all patients with IBS-D symptoms (Rubio-Tapia et al., 2013). Even in IBS-C and IBS-M patients, many experts argue that the low cost and high accuracy of tTG-IgA make screening worthwhile given the consequences of a missed diagnosis.