Positive coeliac blood test? Please don't go gluten free (just yet)

So, you've had a positive coeliac blood test, been referred for a gastroscopy, and now you're on a waiting list that feels like it stretches into next year (and it might!). Meanwhile, you're bloated, brain fogged and wondering why on earth you'd keep eating the thing that might be making you feel this way!

I feel you. I've lived with coeliac disease and IBS myself, and I know how tempting it is to secretly ditch the bread and see if you feel better. But going gluten free before your testing is complete is one of the most common (and most frustrating) detours that my colleagues and I see in clinic.

So here's the short version: keep eating gluten until a specialist has confirmed your diagnosis. Here's why, and how to make it a bit more bearable.

Why gluten needs to stay in the picture

Coeliac testing looks for your body's reaction to gluten:

- the blood test measures antibodies your immune system makes in response to gluten

- the biopsy taken during your gastroscopy looks for damage to the lining of your small intestine (the tiny finger-like villi).

Once you remove gluten, both start to settle down. Antibody levels drop and the gut lining begins to heal, which can leave you with a false negative or "inconclusive" result even though you may, in fact, have coeliac disease.

A positive blood test isn't a diagnosis (yet)

A positive blood test on its own isn't enough to diagnose coeliac disease. It's possible to have a positive blood test and not actually have coeliac disease, which is why a gastroenterologist confirms the diagnosis, usually with small bowel biopsies.

That said, the diagnostic pathway is recently changing. Some children with very high antibody levels can already be diagnosed without a biopsy, and in 2025 the European Society for the Study of Coeliac Disease (ESsCD) updated its adult guidelines to allow a no-biopsy diagnosis for some adults too. This only applies to adults under 45 years, whose antibody levels are at least 10 times the upper limit of normal, confirmed on a second blood test, and who have no "red flag" symptoms. In Australia, a biopsy is still the standard for most adults. Either way, it's your specialist's call, and it still relies on gluten staying in the diet at the time of testing.

"But I feel so much better off gluten"

Feeling better without gluten doesn't confirm coeliac disease. Wheat is high in FODMAPs (fermentable, short chain carbohydrates), which commonly trigger bloating and abdominal pain in people with IBS. Coeliac Australia specifically advises against "trialling" a gluten free diet to see what happens, because symptom improvement isn't diagnostic.

The same goes for symptoms outside the gut, like fatigue, brain fog, headaches or achy joints. These are real and common in coeliac disease, but they’re just as common in people with IBS, non-coeliac wheat sensitivity, iron deficiency, poor sleep or stress. Going gluten free also tends to change a lot more than gluten. Many people end up cooking more and eating less ultra-processed foods, which can make anyone feel better. And our expectations play a bigger role than you might think. In blinded studies, people who believed they’d eaten gluten reported more brain fog, fatigue and headaches, whether or not they actually had. That doesn’t mean your symptoms are “all in your head”. It means that feeling better after removing foods containing gluten, does not tell you why you feel better. Which is why proper testing is so important.

Why getting a clear answer is worth it

Coeliac disease is an autoimmune condition, not just a food preference or ‘intolerance’. A confirmed diagnosis means:

- knowing you need a strict, lifelong gluten free diet, not just "cutting back" or having gluten "when you feel like it"

- coordinated health care follow-up, such as repeat bloods and monitoring of nutrient levels and bone health. A formal diagnosis can also give you access to Medicare rebates for certain tests, and to allied health support (hello, dietitian!) through a GP Chronic Condition Management Plan

- your family members knowing they should be tested too

- no lingering "do I actually have it?" doubt years down the track, which can make it very hard to stay motivated with strict gluten free eating.

If you go gluten free first and later want answers, the only way back is a gluten challenge: deliberately eating gluten again for weeks, usually while feeling rotten. Much wiser to just keep going now and get it done.

How much gluten do I need to eat?

If you're still eating your usual diet (including gluten), keep eating it as normal. Don't start cutting back "a little".

If you've already significantly reduced or removed gluten, it's very important to return to a gluten containing diet for at least six weeks before your blood test or biopsy. There is limited firm consensus about the exact amount of gluten needed, and duration of time necessary for the gluten challenge to warrant an accurate diagnosis. The 2025 ESsCD guidelines recommend a minimum of 3g of gluten a day for six weeks, with higher doses or longer durations (if tolerated) resulting in better accuracy of test results. Coeliac Australia suggests aiming for about 10g a day. In practice, that's roughly four slices of wheat bread, 4 Weet-Bix, or 2 cups of cooked wheat pasta each day. For children, the dose can be halved (about 5 g). Check the right amount for you with your doctor.

According to Coeliac Australia, each of these contains roughly the same amount of gluten as one slice of wheat bread (about 2 - 2.5g gluten):

- 1 Weet-Bix or ½ cup wheat-based cereal (i.e. Sultana Bran, Just Right, Weeties)

- ½ cup cooked wheat pasta

- ½ English muffin or ½ large bread roll

- 4 to 5 crispbreads (e.g. Vita-Weats)

- 8 to 10 crackers (e.g. water crackers or Jatz)

- 2 small sweet biscuits (e.g. Scotch Finger).

It is important to use wheat-based foods as barley, rye and oats aren't recommended for a gluten challenge. Beer and products with "may contains" statements will not provide enough gluten for a challenge either.

For children, a gluten challenge is generally discouraged under age 5 and during the pubertal growth spurt, so talk to your child's doctor or paediatric gastroenterologist about the options.

Making it more bearable

- Start slowly and build up over several days rather than jumping straight to the full daily amount.

- Distribute the gluten food across the day instead of all within the same meal or snack.

- Try lower-FODMAP gluten-containing options, because FODMAPs, rather than gluten itself, are often behind the worst of the symptoms.

- Vital wheat gluten flour is a handy FODMAP reduced option. Most of the starch and carbohydrate in the wheat (including the FODMAPs) is washed away during processing, leaving mostly concentrated gluten protein. About 12g of flour (roughly 9 to 10 g of gluten) a day can be added into a smoothie or yoghurt. Because it's so concentrated, start with a smaller amount and split it across the day.

Often, symptoms are worse at the beginning and can ease within a few days. If you're really struggling, talk to your doctor, rather than just quietly stopping.

Already gluten free and DREADING the gluten challenge?

Ask your GP about a coeliac gene test (HLA-DQ2/DQ8). It's a blood test or cheek swab, and you don't need to be eating gluten for it to be accurate. A negative result means coeliac disease is very unlikely, which could save you a gluten challenge altogether. A positive result cannot diagnose coeliac disease (these genes are common in the general population), so further testing is still needed, and gluten must remain in the diet prior to further testing.

The bottom line

Keep eating gluten until your specialist has confirmed your diagnosis, even if your blood test was positive and even if the wait feels endless. It's a few difficult weeks for a clear answer you'll have for life.

If you're waiting for testing and need help planning a gluten challenge you can actually tolerate, or you've just been diagnosed and don't know where to start, I'd love to help. I'm an Accredited Practising Dietitian who's been there myself, and I see clients Australia-wide via telehealth. Book a consult here.

This post is general information only and isn't a substitute for advice from your own doctor or specialist.

References

- Al-Toma A et al. European Society for the Study of Coeliac Disease 2025 updated guidelines on the diagnosis and management of coeliac disease in adults. Part 1: Diagnostic approach. United European Gastroenterol J 2025;13(10):1855-1886. doi.org/10.1002/ueg2.70119

- Hardy MY et al. Gut 2025;74(6):906-917. PMID: 39961645

- Daveson AJM et al. Masked bolus gluten challenge low in FODMAPs implicates nausea and vomiting as key symptoms associated with immune activation in treated coeliac disease. Aliment Pharmacol Ther 2020;51(2):244-252

- Whelan K. Am J Clin Nutr 2022;115:327-328

- de Graaf MCG et al. The effect of expectancy versus actual gluten intake on gastrointestinal and extra-intestinal symptoms in non-coeliac gluten sensitivity. Lancet Gastroenterol Hepatol 2024.

- Molina-Infante J, Carroccio A. Suspected nonceliac gluten sensitivity confirmed in few patients after gluten challenge in double-blind, placebo-controlled trials. Clin Gastroenterol Hepatol 2017. PMID: 27523634

- Coeliac Australia. Diagnosis. coeliac.org.au/learn/diagnosis/

- Coeliac Australia. Gluten Challenge fact sheet. coeliac.org.au/wp-content/uploads/2023/09/Gluten-Challenge-Fact-Sheet.pdf

- Coeliac Australia. Testing for coeliac disease (health professionals). coeliac.org.au/health-professionals/testing-for-coeliac-disease/