If you’re a Survivor super fan, as a few of us at NiaHealth might be . . . you will remember that Survivor Season 2 led to a life-changing medical diagnosis for one of the contestants. The story goes that Elisabeth (then Filarski) had suffered for years with stomach cramps, low energy, gastrointestinal issues, and other symptoms. She received multiple diagnosis and recommendations but nothing really helped.
Then came weeks in the Australian Outback, where she lived almost entirely on rice and fish - a naturally gluten-free diet. Under those brutal conditions, her symptoms disappeared. She felt better starving in the wilderness than she ever had while eating normally at home.
That realization eventually led to a diagnosis of celiac disease and helped bring more attention to this often misunderstood condition. This has stuck with me, as I was diagnosed with suspected celiac disease the year before (another story for another blog).
People commonly refer to celiac disease as a “gluten allergy.” It isn’t. That distinction matters, because it helps explain the symptoms, the long-term consequences of not treating it, and the tests used to diagnose it.
In celiac disease, gluten does not cause a quick allergic reaction. Instead, it triggers your immune system to attack the lining of your own small intestine. The damage builds over time, which is part of why it can go undiagnosed for years.
The critical thing to understand is this: your body begins producing antibodies against tTG, an enzyme found throughout the body, including the gut lining. This is what makes celiac disease autoimmune, and it’s also why we can measure those antibodies with a blood test.
In a healthy intestine, the villi are tall, finger-like projections that create lots of surface area for absorbing nutrients. In celiac disease, those villi become flattened, inflamed, and much less able to absorb nutrients properly.
Why Symptoms Are So Different From Person to Person?
This is one of the biggest reasons celiac disease gets missed. There is no single “look” to it.
Some people have classic symptoms such as chronic diarrhea, weight loss, bloating, abdominal pain, fatigue, or nutrient deficiencies like low iron, B12, folate, or vitamin D. That is considered the classic picture of celiac, but in reality, celiac disease can show up in many different ways.
One of the most interesting variations I’ve seen in practice is weight loss vs. weight gain.
Weight loss is what most people expect, and it makes sense. When the villi are damaged enough to cause major malabsorption, calories and nutrients simply pass through instead of being properly absorbed.
But weight gain can also happen in undiagnosed celiac disease. Many patients have patchy or milder villous damage, enough to trigger inflammation and symptoms, but not enough to cause severe malabsorption. Some people also eat more to compensate for vague discomfort, and inflammation may affect metabolism and appetite in complex ways.
A normal or higher body weight does not rule out celiac disease.
This wide range of presentations is exactly why celiac disease is so often misdiagnosed as IBS, fibromyalgia, chronic fatigue, anxiety, or simply “stress.”
The Blood Test: tTG-IgA (and Why Total IgA Matters)
The tissue transglutaminase IgA antibody test, or tTG-IgA, is the main screening blood test for celiac disease. It looks for antibodies your body makes against its own tTG enzyme, a marker of the autoimmune reaction seen in celiac disease.
The first thing to know is that for this test to be accurate, the person must be eating gluten. If they are not eating gluten, the body may not be reacting to it, and the test could come back falsely negative.
When someone is eating gluten, tTG-IgA is an excellent test. But it should not be ordered by itself. A total serum IgA should always be checked at the same time.
Test 1: tTG-IgA
Detects antibodies against tissue transglutaminase. This is the main celiac screening test.
Total Serum IgA
Checks whether your body makes enough IgA antibodies for the tTG-IgA test to be reliable.
About 2–3% of people with celiac disease are also IgA-deficient, meaning their bodies do not make enough total IgA. In those people, the tTG-IgA test may come back falsely negative — not because they do not have celiac disease, but because they cannot make enough of the antibody being measured.
Without checking the total IgA level, you may never realize the screening test was unreliable.
If someone is found to be IgA-deficient, the lab usually switches to IgG-based tests instead, such as the deamidated gliadin peptide (DGP) IgG test, which does not depend on IgA production.
The Genetic Test: HLA-DQ2 and HLA-DQ8
HLA-DQ2 and HLA-DQ8 are two genetic markers related to celiac disease. They are not talked about or used as often as tTG-IgA, but they can still be very helpful.
These genes help present modified gluten-related peptides to immune cells, which can trigger the autoimmune response seen in celiac disease.
If neither HLA-DQ2 nor HLA-DQ8 is present, celiac disease is very unlikely. If either one is present, it means celiac disease is possible, but it does not confirm that a person has it.
So this genetic test is most useful for ruling celiac disease out, not confirming it.
It can be especially helpful when the diagnosis is uncertain, when someone has already gone gluten-free before testing (making other tests less reliable), or for screening first-degree family members who may be at higher risk.
When Is a Scope and Biopsy Needed?
An upper endoscopy (EGD) with duodenal biopsies has traditionally been considered the gold standard for confirming celiac disease.
During the procedure, a gastroenterologist takes small tissue samples from the lining of the duodenum, which is the first part of the small intestine. A pathologist then examines those samples under a microscope, looking for inflammation and changes to the villi that are typical of celiac disease.
In adults, most gastroenterology guidelines still recommend biopsy for confirmation in most cases, although this is an evolving area. Notably, recent European guidelines (2025) now conditionally support a no-biopsy diagnosis for adults under 45 whose tTG-IgA levels are very high (≥10 times the upper limit of normal). This approach is still being evaluated more broadly, and practices may vary.
For accurate results, the patient must be actively eating gluten when tested — both for blood work and for biopsy. Going gluten-free before testing can make results appear normal and make diagnosis much more difficult.
Why Eating Gluten-Free Actually Matters Once Diagnosed
This is not a lifestyle preference or a wellness trend. For someone with confirmed celiac disease, a strict gluten-free diet is medical treatment, and currently, it is the only treatment.
That is why saying “a little bit won’t hurt” can be genuinely dangerous for someone with celiac disease. Even tiny amounts of gluten can trigger the immune response, and intestinal damage can happen even when the person feels no symptoms at all. This damage increases the risk of certain cancers, bone loss, infertility, nerve damage, and poor nutrient absorption.
Strictly following a gluten-free diet is not just about feeling better in the moment. It is about preventing serious, long-term harm
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