What Are the Symptoms of Undiagnosed Celiac Disease?

Undiagnosed celiac disease can produce a remarkably wide range of symptoms, and many of them have nothing to do with the gut. While chronic diarrhea, bloating, and abdominal pain are the textbook signs, only about a third of adults diagnosed with celiac disease actually present with those classic digestive complaints.¹ The rest show up with persistent fatigue, unexplained anemia, thinning bones, skin rashes, fertility problems, or neurological changes that no one initially connects to a food intolerance. That gap between what people expect celiac disease to look like and what it actually looks like is a major reason the condition goes undiagnosed for years.

The Classic Digestive Picture

The symptoms most people associate with celiac disease are the gastrointestinal ones. Chronic or intermittent diarrhea, abdominal pain, bloating, and unintended weight loss form the “classical” presentation. In one large cohort study in the Netherlands, diarrhea was reported by about 37% of patients at diagnosis, abdominal pain by about 33%, and weight loss by roughly 32%.¹ A separate Canadian study found that abdominal pain and bloating were the most commonly reported symptoms at diagnosis, affecting about 85% of patients, with diarrhea following at roughly 72%.² These numbers vary depending on how the question is asked and when in the diagnostic process symptoms are assessed, but the overall picture is consistent: digestive symptoms are common but far from universal.

The underlying problem is damage to the lining of the small intestine. Gluten triggers an immune reaction that flattens the tiny finger-like projections (villi) responsible for absorbing nutrients. That damage impairs absorptive function, which can lead to loose stools, gas, and the cramping and distension that make daily life miserable.³ But the severity of intestinal damage does not always correlate neatly with the severity of gut symptoms, which is why so many people slip through the diagnostic net.

Atypical Gut Symptoms That Get Overlooked

Celiac disease does not always mean diarrhea. Some people experience the opposite: chronic constipation was reported by about 10% of patients in the Dutch cohort study, and acid reflux by about 12%.¹ These are symptoms more commonly associated with irritable bowel syndrome or gastroesophageal reflux disease, and that resemblance creates a well-documented diagnostic trap. A large study found that 16% of people eventually diagnosed with celiac disease had previously received an IBS diagnosis, compared to about 5% of matched controls. When the researchers looked at IBS-related treatments rather than just diagnostic codes, the numbers were even more striking: 28% of celiac patients appeared to have been treated for IBS before their celiac diagnosis.⁴ In adults, celiac disease is sometimes discovered incidentally during an endoscopy performed for reflux symptoms.⁵

The IBS misdiagnosis pattern is not just a brief detour. That same study found a clear excess of IBS diagnoses stretching back a full decade before celiac disease was finally identified.⁴ If you have been told you have IBS but the standard advice has not helped, celiac disease is worth ruling out with a blood test.

Persistent Fatigue and Brain Fog

Extreme tiredness is one of the most commonly reported symptoms at diagnosis, affecting roughly three-quarters of patients in one study.² Fatigue was also reported by about 35% of patients in the Dutch cohort.¹ This is more than ordinary tiredness; people describe a bone-deep exhaustion that sleep does not fix, likely driven by a combination of nutrient malabsorption, chronic inflammation, and anemia.

Many people with celiac disease also describe cognitive difficulties commonly called “brain fog.” The most frequent descriptions include difficulty focusing, difficulty thinking clearly, and trouble finding the right words during conversation.⁶ These cognitive symptoms can be disabling in work and social settings, and they are easy to attribute to stress, poor sleep, or aging rather than an underlying autoimmune condition.

Iron Deficiency Anemia as the Only Clue

Anemia was present in roughly 68% of patients at the time of celiac diagnosis in one Canadian study.² What makes this especially tricky is that iron deficiency and anemia can be the presenting feature of celiac disease even when there is no diarrhea or weight loss at all.⁷ Iron is primarily absorbed in the upper part of the small intestine, which is exactly where celiac disease does the most damage. Someone might visit their doctor for fatigue or shortness of breath, get a blood test showing low iron, take iron supplements that do not bring levels up because the absorption problem persists, and go through that cycle for years before anyone considers testing for celiac disease.

If iron supplementation is not raising your levels, or if anemia keeps returning without an obvious cause like heavy menstrual bleeding, celiac disease should be on the list of possibilities.

Skin and Mouth Signs

Dermatitis herpetiformis is a blistering, intensely itchy skin rash that appears on the elbows, knees, buttocks, and scalp. It is considered a direct cutaneous manifestation of celiac disease and shares the same genetic background, gluten-dependent intestinal damage, and antibody response. Researchers now regard it as a late manifestation of subclinical celiac disease, meaning the gut damage has been present for some time before the rash appears.⁸ Many people with dermatitis herpetiformis have minimal or no gut symptoms, so the rash itself may be the first recognizable sign of the disease.

Inside the mouth, celiac disease leaves its own marks. Dental enamel defects, which appear as pitting, grooving, or discoloration of the teeth, are a common finding in children with celiac disease. These defects develop because celiac disease disrupts the normal formation of enamel during the years when permanent teeth are being built. Recurrent mouth ulcers (aphthous stomatitis) are also common.⁹ These oral findings can serve as early noninvasive clues to undiagnosed celiac disease, and dentists are sometimes the first to spot them. Systematic review evidence suggests that recognizing these enamel patterns may signal celiac disease even when gastrointestinal symptoms are absent.¹⁰

Bone Loss and Fractures

Osteoporosis is a relatively frequent atypical presentation of celiac disease, especially in adults, and undiagnosed celiac disease can be the underlying cause of osteoporosis and related fractures.¹¹ In some cases, bone loss is the sole presenting feature, with no gut symptoms at all.¹² The mechanism involves two factors working together: the damaged intestine absorbs less calcium and vitamin D, and chronic inflammation simultaneously accelerates bone breakdown.¹³

If you have been diagnosed with low bone density at a younger age than expected, or you have had a fracture from relatively minor trauma, it is worth asking whether celiac disease could be the root cause. Treatment with a gluten-free diet, by allowing the intestine to heal, can improve calcium absorption and slow or partially reverse bone loss.

Neurological and Psychiatric Symptoms

Celiac disease can affect the nervous system in ways that seem entirely unrelated to the gut. The range of neurological manifestations includes peripheral neuropathy (tingling, numbness, or pain in the hands and feet), cerebellar ataxia (problems with balance and coordination), epilepsy, chronic headaches, and cognitive impairment.¹⁴ Depression is also reported at higher rates. These neurological presentations are rare in children but may affect as many as 36% of adult patients.¹⁵

The mechanisms are not fully mapped out. Some of the neurological damage appears to stem from nutrient deficiencies that develop over time as malabsorption worsens, particularly B vitamins and vitamin E. There is also growing evidence for a direct neuroinflammatory process driven by the immune response itself. For someone who develops unexplained neuropathy or balance problems, celiac disease is not the first thing most neurologists will think to test for, which contributes to the diagnostic delay.

Fertility and Pregnancy Complications

Undiagnosed celiac disease has been linked to impaired fertility and adverse pregnancy outcomes, likely through a combination of immune-mediated mechanisms and nutrient deficiency.¹⁶ A meta-analysis quantified this more precisely: the odds of having undiagnosed celiac disease were about five times higher in women with unexplained infertility and about six times higher in women experiencing recurrent miscarriage, compared to the general population. For intrauterine growth restriction, the odds were nearly nine times higher.¹⁷

Delayed puberty and absent menstrual periods (amenorrhea) are also recognized presentations, particularly in adolescents.¹⁸ The reproductive effects are not limited to women; there is evidence of reduced fertility in men with untreated celiac disease as well, though the research base is smaller. The encouraging part is that many of these reproductive problems improve or resolve after starting a strict gluten-free diet, once the intestine heals and nutrient status normalizes.

Unexplained Liver Enzyme Elevation

An unexpected finding on routine blood work can sometimes be the thread that unravels a celiac diagnosis. Mildly elevated liver enzymes, with no other identifiable liver disease, have been found in up to 9% of patients with unexplained aminotransferase elevations.¹⁹ This pattern, sometimes called “celiac hepatitis,” is the most common form of liver involvement in celiac disease. The elevations tend to be mild and nonspecific, and in most patients they return to normal after starting a gluten-free diet.²⁰ If your liver enzymes are persistently elevated and the usual causes (alcohol, viral hepatitis, fatty liver disease) have been excluded, celiac testing is a reasonable next step.

How Children Present Differently

Children with celiac disease can show a somewhat different symptom profile than adults. While chronic diarrhea and abdominal distension are common in young children, growth failure, short stature, and failure to thrive may be the most prominent signs.¹⁸ Children under age three with celiac disease are more likely to present with significant growth disturbance, and those with more severe intestinal damage tend to have worse growth impairment.²¹

Older children may instead present with poor growth as their sole clinical feature, without the vomiting and diarrhea more typical of younger kids. These children tend to have milder intestinal changes on biopsy and higher hemoglobin levels, making the diagnosis less obvious.²¹ Pediatric guidelines recommend testing for celiac disease when children have unexplained chronic constipation, recurrent mouth ulcers, delayed puberty, or unexplained iron deficiency anemia, not just digestive complaints.¹⁸

“Silent” Celiac Disease and Screening

Some people have confirmed celiac disease on blood tests and intestinal biopsy yet report no obvious symptoms. This is called silent celiac disease.²² But that label can be misleading. Research has found that screening-detected celiac disease is rarely truly silent; rather, the symptoms are present but unrecognized by the patient or their doctor.²³ People who have lived with vague fatigue, mild bloating, or intermittent discomfort for years may have normalized those feelings, only recognizing them as symptoms after a gluten-free diet makes them feel genuinely well for the first time.

Screening is particularly important for first-degree relatives of someone with celiac disease. Studies show that roughly 5% to 10% of first-degree relatives have serologic and biopsy evidence of celiac disease, and these cases cluster in about a quarter of affected families.²⁴ Not all of those detected through screening are asymptomatic; many have symptoms they had not attributed to celiac disease.

Long-Term Risks of Staying Undiagnosed

Beyond the day-to-day burden of symptoms, leaving celiac disease untreated carries more serious long-term consequences. Ongoing intestinal inflammation and malabsorption can lead to progressively worsening osteoporosis and bone fractures.²⁵ There is also an established association with certain cancers. Celiac disease is linked to an elevated risk of intestinal lymphoma, particularly a rare and aggressive form called enteropathy-associated T-cell lymphoma, as well as adenocarcinoma of the small intestine, pharynx, and esophagus.²⁶

The magnitude of the lymphoma risk has been studied in population-level data. One study found the odds of non-Hodgkin lymphoma at any site were about three times higher in people with celiac disease, while the odds for gut lymphoma specifically were roughly 17 times higher, and for T-cell lymphoma about 19 times higher.²⁷ These are relative risks, and the absolute risk of these cancers remains low because they are rare to begin with. But early diagnosis and treatment with a gluten-free diet are considered important for reducing this risk.²⁸

When to Push for Testing

One of the most frustrating aspects of celiac disease is that its symptoms overlap with so many other conditions. Fatigue could be anything. Bloating could be anything. Anemia, brain fog, tingling hands, a skin rash, a run of miscarriages, mildly abnormal blood work: each of these has a long list of possible explanations, and celiac disease is rarely at the top. The average diagnostic delay in adults has historically been measured in years, not months.

The good news is that the initial screening test is a simple blood draw. The standard test looks for antibodies against tissue transglutaminase (anti-tTG IgA), and it is highly accurate when the person has been eating gluten regularly. If you have a combination of the symptoms discussed here, especially if you have a first-degree relative with celiac disease, type 1 diabetes, or another autoimmune condition, asking your doctor for this blood test is a reasonable first step. The one critical detail is that you need to be eating gluten at the time of testing; going gluten-free before the test can produce a falsely negative result, which is one of the most common avoidable mistakes in celiac testing.