If you're reacting to certain foods, bloated most days, or just tired of guessing what's behind it, the most useful first step often isn't the test you'd expect. Before any food intolerance panel, it's worth considering coeliac disease, a diagnosable condition with a clear evidence base, because going gluten-free before testing can make it much harder to detect. From there, the right next step depends on what you're actually experiencing: a possible true allergy, a specific sugar you may not digest well, or a broader pattern that's better sorted out with a structured investigation than a single test.
This guide walks through what's available, a sensible order to consider things in, and what each result can and can't tell you, including an honest look at where IgG food intolerance testing fits, and where it doesn't.
What food intolerance actually means
"Food intolerance" isn't a single condition. It's an umbrella term covering several different mechanisms that can produce overlapping symptoms such as bloating, gas, fatigue, headaches or skin changes. It's also frequently confused with two things it isn't:
- Coeliac disease. An autoimmune condition where eating gluten triggers immune-mediated damage to the small intestine. It has a defined blood-testing pathway and a clear diagnostic process, and it should be investigated with testing rather than assumed either way.
- Food allergy. An immune (IgE) reaction that can be rapid and, in severe cases, dangerous. Allergy symptoms (such as hives, swelling, or breathing difficulty) tend to be more obvious and immediate than intolerance symptoms, and are typically reproducible and fast in onset [1].
- Food intolerance itself. This covers the rest: lactose intolerance, fructose malabsorption, and sensitivities that some people find build up more gradually rather than appearing right after eating [1].
Because these can feel similar, investigating them in the wrong order is a common reason people end up confused, or cut out foods they didn't need to. That's the logic behind the order this guide suggests.
Step 1: Consider coeliac disease first
Coeliac disease affects an estimated 1% of the population, and most cases remain undiagnosed [7], partly because symptoms like bloating, fatigue, brain fog and iron deficiency overlap so heavily with general food intolerance. Testing starts with a blood test: i-screen's Coeliac Check screens for tissue transglutaminase (tTG) IgA and deamidated gliadin peptide (DGP) IgG antibodies, markers used to help investigate coeliac disease, for $69, ordered online with no GP referral needed. A positive or borderline blood test is a screening result that points toward the need for further assessment (often including a specialist referral and small-bowel biopsy), not a stand-alone diagnosis.
The reason this comes first, ahead of any food intolerance panel, isn't cost. It's that coeliac disease is a diagnosable, medically managed condition, and antibody testing works properly only while you're still eating gluten regularly. If you cut gluten out before testing, antibody levels can fall and gradually normalise, which can produce a falsely negative or falsely reassuring result, and this effect grows the longer gluten has been avoided [4,5]. In fact, once someone has been on a gluten-free diet, standard antibody tests can miss around half of those with ongoing gut damage [6]. That means a genuine diagnosis needing ongoing medical management can be missed. If coeliac disease is even a possibility, it's best to test before you change your diet, not after.
If you've already gone gluten-free and want to investigate retrospectively, a GP or specialist can advise on the options, which may include genetic testing (HLA-DQ2/DQ8 typing) or a supervised gluten reintroduction before repeat testing [4]. Genetic testing can't confirm coeliac disease on its own, but a negative result makes it very unlikely. For more on how the two conditions differ and how each is diagnosed, see i-screen's guide to gluten sensitivity vs coeliac disease.
Step 2: Could it actually be a true food allergy?
If your reactions are fast, typically within minutes, and involve hives, swelling, tingling or breathing difficulty, that pattern is more suggestive of a true food allergy than an intolerance, and it's worth investigating separately [1]. Food allergy is more common in adults than many people realise, population surveys suggest it affects around 1 in 10 adults [8,9], and when it's present the reaction is reproducible and rapid, which sets it apart from the slower, non-immune mechanisms behind most intolerances [1]. Food allergy involves the immune system's IgE antibodies, a different mechanism to the food intolerance panels covered below, and it's tested differently. i-screen's Allergy Test screens IgE responses across 27 common allergens, including a range of foods, for $129. IgE testing works best alongside your clinical history, it doesn't catch every genuine reaction, and a positive result can occur without a real-world allergy [1]. If you've ever had a severe or fast reaction involving breathing difficulty or swelling, seek medical assessment rather than relying on a test. For a fuller breakdown of how allergy and intolerance differ, see Food Allergy vs Food Intolerance.
Step 3: Where IgG food intolerance testing fits, honestly
Once coeliac disease and true allergy are reasonably considered, this is the point where many people expect a single test to give a clear answer. It's worth being upfront about what the evidence actually says.
IgG antibodies to food are common in the general population, including in people with no food-related symptoms at all, an IgG response reflects ordinary, repeated exposure to a food rather than disease [2,3]. Expert consensus and gastroenterology guidelines are clear that food-specific IgG/IgG4 panels are unproven, have not been validated, and are not recommended for diagnosing food allergy or intolerance [1,3]. In plain terms: an IgG panel flagging a food generally indicates that you've eaten it and your immune system has been exposed to it, not that the food is making you unwell.
That doesn't mean an IgG result can never be part of a wider process, but it isn't a diagnosis, and it shouldn't be the first test you reach for. If used at all, it's best treated as one piece of information to discuss with a practitioner, alongside a symptom diary and, usually, a supervised elimination and reintroduction process. i-screen's Food Intolerance Test (IgG, 96 Foods) is priced from $399, with larger panels available. If you go this route, treat the result as a conversation starter rather than a verdict, and see the elimination diet guide below for how to actually check whether a flagged food is doing anything.
Step 4: Testing a specific suspect
If a particular food or food group is your main suspect, there are more targeted options than a broad IgG panel:
- Lactose Intolerance Breath Test ($149). A breath test measuring hydrogen and methane after a lactose drink, to help assess whether lactose specifically is contributing, useful if dairy is your leading suspect rather than food in general. Lactose breath testing performs well for detecting lactose malabsorption [11].
- FODMAP Test ($289). A breath test covering lactose and fructose malabsorption (with optional sucrose, sorbitol and mannitol add-ons), relevant if bloating, gas and IBS-type symptoms are the dominant pattern rather than a specific food reaction.
Breath tests are best interpreted alongside symptom tracking rather than in isolation, since a subset of people are non-hydrogen producers whose results can look falsely reassuring [10]. Both tests sit within i-screen's broader Gut Health & Digestion range, which is worth a look if digestive symptoms, rather than food reactions specifically, are the main thing you're trying to understand. i-screen's guide to which gut test you actually need breaks down the fuller line-up if that's a better fit.
Step 5: The elimination diet, testing's other half
No blood or breath test replaces observing how your body responds to a food. For a suspected true allergy, the gold standard is a supervised oral food challenge, not a do-it-yourself elimination diet, and this should always be done under medical supervision [2]. For non-allergic intolerance, a supervised elimination and reintroduction diet is the most practical way to confirm a suspected trigger rather than just narrow it down. Either way, test results (coeliac, allergy, IgG or breath test) are most useful as a way to decide where to start, not as a substitute for the process itself. Because cutting foods out can affect nutrition, and, in the case of gluten, coeliac testing, it's best done with guidance from a qualified practitioner. i-screen's step-by-step guide to starting an elimination diet covers how to run one properly, and its companion piece on daily bloating is a useful read if bloating specifically is driving the search for a test.
A simple decision guide
| If this describes you | Consider starting here |
|---|---|
| You haven't investigated coeliac disease and you're still eating gluten | Coeliac Check ($69) |
| Reactions are fast and severe (hives, swelling, breathing issues) | Seek medical assessment; Allergy Test, IgE ($129) can be part of the workup |
| Coeliac disease and allergy have been considered, symptoms persist | Structured elimination diet, with an IgG panel as one optional input for your practitioner |
| Dairy specifically is the main suspect | Lactose Intolerance Breath Test ($149) |
| Bloating and gas are the leading symptoms | FODMAP Test ($289), or i-screen's wider gut health range |
How much does a food intolerance test cost in Australia?
It depends on which test actually matches your symptoms, which is the point of testing in a sensible order rather than reaching for the broadest (and most expensive) panel first. As a guide: Coeliac Check is $69, an IgE Allergy Test is $129, a Lactose Intolerance Breath Test is $149, a FODMAP Test is $289, and IgG food intolerance panels start from $399 for 96 foods, rising to $789 for the largest 240-food panel. None of these require a GP referral to order.
FAQs
Should I consider coeliac testing before a food intolerance test? Generally, yes. Coeliac disease has a clear testing pathway and is important to investigate first, particularly because going gluten-free before testing can lower antibody levels and mask a genuine diagnosis [4,5]. Food intolerance testing looks at a much broader and less clear-cut picture, and is usually more useful once coeliac disease and true food allergy have been considered.
Do I need to stop eating a food before testing for it? No, and for coeliac disease specifically, you shouldn't. Cutting out gluten before coeliac testing can affect the accuracy of the result, and the longer it's been avoided the greater the effect [4,5]. Keep eating normally until you've had the relevant test, then use an elimination diet afterwards if you want to check how a specific food affects you.
How long does it take to get food intolerance test results? Turnaround varies by test type. Blood-based tests like the Coeliac Check and Allergy Test are typically processed within a similar timeframe to routine pathology, while IgG panels and breath tests can take a little longer given the number of items analysed. Exact timeframes are shown on each test's product page before you order.
Can I order these tests without a GP referral? Yes. Every test in this guide, Coeliac Check, Allergy Test, IgG food intolerance panels, Lactose Intolerance Breath Test and the FODMAP Test, can be ordered online through i-screen without a GP referral. Your kit or pathology request is sent directly to you, and you can take any result to your GP or another qualified practitioner to discuss what it means for you.
The bigger picture
Testing in a sensible order beats testing everything at once. Considering coeliac disease and true allergy first, then using a structured elimination diet alongside any broader panel, gives you something more workable than a stack of results that raise more questions than they settle.
This article is general information only and is not a substitute for professional medical advice. Food intolerance, allergy and coeliac screening provide information about markers and patterns relevant to how your body responds to food; they do not, on their own, diagnose coeliac disease, food allergy, or any other medical condition. If you have persistent or concerning digestive symptoms, unintentional weight loss, rectal bleeding, or iron deficiency, see your GP or a qualified healthcare professional rather than relying on testing alone.
