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The Most Common Signs of Gluten Intolerance

Erica Dermer

Medically reviewed by

Stefano Guandalini, MD


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Gluten seems to be the newest nutritional villain found on every menu, but does it deserve to be? Gluten-free diets are more popular than ever, even for those that are not diagnosed with celiac disease. Is there a real reason to avoid gluten or is it just another passing fad diet? 

Surveys have shown anywhere from 2% to up to 20% of people avoid (all or some) gluten without a celiac disease diagnosis. And if you have done an internet search in the past few years, it’s no mystery why. Gluten has been negatively linked to just about every health concern - from cognition to skin issues. While gluten may seem like a new topic of discussion, celiac disease has been around for hundreds of years. Even non-celiac gluten sensitivity (or gluten intolerance) was originally described in the 1980’s. Research has shown that both those getting diagnosed with celiac disease, and those without celiac disease, but still on a gluten-free diet have increased over the years. 

But what’s the real issue with gluten? Does everyone really have a problem eating gluten or is it just hype? What is gluten intolerance or gluten sensitivity? Let’s find out more about this mysterious condition! 

How do you diagnose gluten intolerance? 

If you think that you experience symptoms after eating something containing gluten like pizza, pasta, bread, or even beer, you could be gluten intolerant. But first, it’s important to rule out diseases and conditions that can be easier to diagnose, like celiac disease. 

First rule out celiac disease

Celiac disease is a common autoimmune disorder that affects about 1 in 100 people. Those with celiac disease suffer from digestive issues and body-wide symptoms, much like those with gluten sensitivity. However, celiac disease is a common disease with a set diagnostic standard in place - a positive blood test screener, followed by a positive upper endoscopy and biopsy. It’s important to keep eating gluten during this blood test and until the endoscopy is performed to properly diagnose celiac. If you go on a gluten-free diet too early, you won’t get accurate results!

If you are negative for the celiac disease screening blood test and the intestinal biopsy, you may still have a problem with gluten-containing foods! If you are sure that gluten-containing foods are the culprit to your sensitive belly, then keep investigating!

Next, rule out other gastrointestinal conditions. 

After you exclude celiac disease, you’ll also need to exclude other conditions that may be the cause of the issue. Rule out an IgE wheat allergy, and exclude wheat-induced non-IgE mediated food allergies like FPIES, EOE (although they may overlap). You will also need to be aware of any recent red-flag symptoms like weight loss, bleeding from the rectum, anemia, fever, etc. that may indicate an infection or inflammatory bowel disease (IBD). While this list may seem overwhelming, a gastroenterologist can help you distinguish what you’re going through with other similar issues! Once these are all taken into consideration, and there are no other answers, an intolerance to gluten (or possibly - see below - to wheat) can be diagnosed . 

Is there a test for gluten sensitivity? 

Unfortunately, current research has not found a specific biomarker for a sensitivity to gluten. You can’t go to your doctor’s office and order a blood test to find out if you’re sensitive to gluten, because there isn’t one yet. And considering that under the term of “gluten sensitivity” there may well be different entities (see below) it is unlikely that any specific test would be valid for all. Thus, currently, gastroenterologists work on a diagnosis of exclusion, as previously mentioned. That is largely based on the patient’s subjective symptoms.

What causes gluten intolerance? 

While an exact answer isn’t known, researchers have an idea on what might cause this sensitivity, or what part of wheat (it may or it may not be gluten!) is triggering a reaction in those with this sensitivity. Because of this, you might also hear the phrase non-celiac wheat sensitivity - as some researchers believe the wheat and its protein may be an issue, not the gluten itself. 

In fact, there are other components of wheat that are likely culprits for this entity, that should be properly called “Non-celiac wheat sensitivity”.

Amylase Trypsin Inhibitors (or ATIs) are specific proteins found in wheat (and separate from gluten) that researchers think might trigger a reaction. 

FODMAP (present in milk and in a variety of plants and cereals, including wheat and rye). FODMAPs are fermentable sugars found in some specific foods that not being fully degraded during their flow through the digestive system, draw water into the gut, and are fermented by bacteria. For some people, this fermentation causes pain, gas, and bloating. Some researchers have indeed shown that FODMAPs - specifically the fructans and those fermentable sugars found in wheat  - might be the cause of GI upset. 

Additionally, it must be acknowledged that research has also shown that in many cases, patients who believe to have non-celiac wheat sensitivity when challenged under close scrutiny in double-blind, placebo controlled studies, fail to show reaction to hidden gluten and even may react to the innocuous placebo. Thus, this disorder may also be, in a portion of patients, a functional disorder, now better defined “disorders of brain-gut interaction.

Common signs of an issue with gluten

Chances are, you don’t have a silent problem with gluten - if you have an issue, your body will tell you! But those signs might be different for everyone, from GI symptoms like gas and bloating to brain fog and headaches. How can all of these be related to just one type of food? Gluten can affect your entire body, especially if you have celiac disease. But those with other gluten-related disorders like gluten intolerance can also feel its effects. 

Excess gas/bloating

Feel like a balloon after eating gluten? Abdominal pain, bloating, and distention, as well as excess gas, have all been reported in both non-celiac gluten sensitivity and IBS. 

If you’ve already been diagnosed with celiac disease, an episode of gas or bloating - while not necessarily due to a gluten exposure - may mean you’ve been exposed to gluten through cross contamination or accidental exposure. If you've tried to stop bloating at home with no success, it’s important to have regular follow up with your gastroenterologist if you continue to experience bloating or gas after you’ve been on a strict gluten-free diet. 

A change in bowel habits: diarrhea, and constipation

New diarrhea, constipation, or just an overall change in bowel habits, are common symptoms of celiac disease or gluten intolerance. But a change in consistency of your poop, or frequency of your bathroom habits are a pretty common occurrence for many digestive diseases. These bathroom issues happen with autoimmune diseases like IBD, irritable bowel syndrome, food sensitivities and food allergies, and even food poisoning. 

While it may seem strange to look into the toilet bowl after you go to the bathroom, it’s important for your overall health! You should regularly check if your poop is unusual and if anything changes over time. 

  • Is it runny like water or hard like rabbit pellets? 
  • Does it occur with pain - and is the pain better after you go to the bathroom? 
  • Is it like this all the time, or is this a new occurrence? 
  • Does it happen after you eat something particular? Are you going to the bathroom more often than usual or less often? 

If it’s overwhelming to remember, consider keeping a journal of your bathroom habits, along with a food diary. It may be helpful for your gastroenterologist to know! 

Brain fog

For those with celiac disease, neurological and psychiatric symptoms are common. In fact, it can sometimes be the only symptom that indicates celiac disease! Studies show that “brain fog” is a common occurrence for those with both celiac disease and those self-diagnosed with gluten sensitivity. While brain fog may feel scary at the time, thankfully, there seems to be no risk for cognitive decline in people who eat gluten (specifically women) long-term, without celiac disease. 

Neurological issues: Headaches, migraines, and neuropathy

We know that those with celiac disease can experience inflammation in the nerves on a gluten-containing diet. Gluten can even cause ataxia (difficulty with walking and loss of balance) and neuropathy (tingling or loss of sensation in the nerves). However, those without celiac disease often complain about nerve issues as well. 

Severe headaches or migraines might be something more - caused by gluten. While this has been demonstrated in celiac disease, more studies need to be done to find what causes headaches in those with gluten sensitivity. 

Mental health and gluten

Are you not yourself when you’ve had gluten? You’re not the only one. Gluten can trigger an immune response that is linked to neurological and psychiatric symptoms. It has been linked to depression, anxiety, and psychosis. One study found that even short term (3 days) gluten ingestion can cause feelings of depression, even without a change to GI symptoms! 

Fatigue and tiredness

Are you exhausted after a meal containing gluten? What if you accidentally had a bite of regular pizza when you’ve been gluten free? If the thought of that makes you want to curl into a ball under a cozy blanket, you might be experiencing a reaction to gluten. Research studies have shown that reintroduction of gluten after a gluten-free diet causes fatigue (a whole body tiredness that can’t be fixed by sleep). And tiredness (or feeling sleepy and exhausted) was one of the top self-reported symptoms of those with gluten sensitivity. This might be due to the low-grade inflammation that can be present in those with gluten issues! 

For those with celiac disease, fatigue and tiredness are common symptoms of being glutened, as well as  frequent symptoms that were resolved after going on a gluten-free diet. This could be because your body is unable to properly absorb vitamins, minerals and nutrients that are necessary for feeling your best. Another reason for fatigue could be anemia, often found in undiagnosed celiac disease patients. 

Autoimmune disorders

It’s common to have another autoimmune disorder if you already have one - like the increased chance of diabetes or thyroid disease once you have celiac. In fact, several autoimmune diseases leave you more likely to have celiac disease, which is why a family history should be part of every celiac disease screening process. 

But research has shown that those with gluten intolerance, or non-celiac gluten sensitivity, might also have an association with autoimmune disorders, along with a history of food allergies in childhood. More research is needed to understand this relationship. 

Joint pain

Those with gluten sensitivity may suffer from fibromyalgia or fibromyalgia-like syndromes, and have joint and muscle pain. While there have been some studies showing that those with sensitivity had improvement of joint pain on a gluten-free diet, specifically back pain, the evidence is still considered weak. Joint pain should always be evaluated by a physician to rule out other issues like arthritis or other inflammatory conditions. 

Skin rash

When it comes to gluten, the skin is not spared from its effects. For those with celiac disease, some suffer from an itchy, scaly rash called dermatitis herpetiformis. This can turn into blisters that appear on the buttocks, knees, back, elbows, scalp, and even under armpits. This rash is an outward presentation of celiac disease, and can be the only symptom that alerts a doctor (even a dermatologist) to a celiac disease diagnosis. Thankfully DH typically goes away when gluten is removed from the diet. However, prescription medications are often necessary. 

For those with gluten sensitivity, the skin may still be involved. Rashes, eczema, and even something like psoriasis are often cited as skin issues when eating gluten, or when gluten is reintroduced back into the diet. 

Gynecologic Issues

There’s an established connection between untreated celiac disease and reproductive health. Ongoing fertility issues, miscarriages and low birth weight could be a sign of celiac disease. Those with gluten sensitivity may suffer more from issues in their reproductive health, including issues with menstrual symptoms, recurrent vaginitis, cystitis, and possibly endometriosis. While it may seem strange to mention your reproductive health to your GI, or your diet to your OBGYN, these issues might be related! 

How do you treat gluten sensitivity? 

The basic treatment plan for someone who is sensitive to gluten is to completely remove gluten from the diet. Once you start to feel better, and you’ve been tested negative for celiac disease, you can add back in small amounts of gluten to your diet. Experiment to see if you can tolerate small amounts of gluten with a more liberal diet. This adds back in key nutrients and can help the stress and financial burden of a strict gluten-free diet. 

If you still have symptoms after removing gluten from your diet, try a low FODMAP diet, with the assistance of a dietitian. If symptoms still persist, even after a low-FODMAP and gluten-free diet, please see your gastroenterologist for further exploration. 

If you meet the criteria for IBS also, you can consider specific probiotics or a prescription antibiotic specifically for IBS-D with the help of your gastroenterology team. 


Yes, gluten can cause very real problems! Symptoms like brain fog, tiredness, bathroom issues, and even mental health issues can stem from gluten. And if you have an issue with gluten, you’re not alone. Those with celiac disease need to avoid gluten for the rest of their lives, or can be at risk for much more serious health problems. Those who have ruled out celiac disease and a wheat allergy who have issues digesting gluten are considered to be sensitive to gluten, or gluten intolerant. While the issue may stem from separate proteins or carbohydrates found in wheat - a gluten-free diet is usually the answer. Remember, it’s important to consult with professionals like a dietitian or physician, as going gluten-free without guidance may result in nutrient deficiencies and a less-diverse gut microbiota!

Updated on
January 28, 2022
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