Do Food Intolerance Blood Tests Work?

We are living at a time now where interest surrounding digestive health is at an all-time high.

But that also means that misinformation in this subject area is rampant as more and more people rely on unreliable sources of health information.

In today’s article I will help you to understand what a food intolerance is, why it’s very different than a food allergy and why there is no quick or easy test ( no matter what anyone tells you) to figure out which foods you are intolerant to.

What is a food intolerance?

A food intolerance occurs when your body, for whatever reason, struggles to properly digest a certain food or food component.

This frequently results in gas, bloating, constipation and diarrhea.

One of the hallmark characteristics of food intolerance is that it is dose-dependent.

Meaning that small amounts of a potentially bothersome food may not cause you issues, while moderate to larger amounts will.

There are a wide variety of foods that someone could potentially be intolerant to, and we all experience intolerance differently.

Lactose intolerance is probably the most well recognized example of food intolerance.

People with lactose intolerance lack the enzyme required to break down the sugar in dairy (lactose), thus experiencing the symptoms outlined above.

A food intolerance is unpleasant and uncomfortable, but not life threatening.

There is NO formal test that can be done to test for food intolerance ( more on this to come).

How is an intolerance different than an allergy?

A food allergy is an immune, rather than purely gastrointestinal, response to food.

They are very severe reactions that can be life threatening.

Symptoms include hives, tingling, swelling , trouble breathing, digestive symptoms.

Common allergen foods include peanuts, tree nuts, soy eggs, wheat, shell fish and so on.

In Canada, there are more people who think they have an allergy than who have actually had an allergy diagnosed by a doctor.

This suggests that some Canadians potentially confuse allergy and intolerance.

If you suspect a food allergy you should consult with your doctor, who will be able to help you to determine whether you have a true allergy or potentially just an intolerance.

A food allergy can ONLY be diagnosed by a doctor through skin or blood tests.

There is no magical food intolerance test

Food intolerance is probably one of the most complex topics in modern popular nutrition.

This is largely due to the fact that living with digestive health issues can be so frustrating and uncomfortable that it leads people to seek quick solutions.

Unfortunately, there is not always such thing as a quick fix when it comes to determining food intolerance issues.

You may have taken, heard of or been suggested to take an IgG test, also known as a food-specific immunoglobulin G test.

This test is marketed as a “food sensitivity” test, but is ultimately a food intolerance test.

It supposedly helps individuals identify the specific foods they are intolerant to, for the small price of $400-700.

Some insurance companies will even offer partial or complete reimbursement for this test.

There’s only one problem though… there is no evidence that these tests actually work as described.

Here’s what The Canadian Society of Allergy and Clinical Immunology (CSACI) has to say about them:

  1. There is no evidence that suggests the IgG test can predict a negative reaction to food, which means that the scores this test offers are essentially just reflective of normal fluctuations in response to different food that healthy adults and children would expect to see.


  1. The use of this test increases the probability that you will make an unnecessary dietary restriction which, if not properly addressed, could reduce the quality and balance of your diet and detract from your overall health.


For reference, the CSACI is a group of medical doctors that are much more thoroughly trained and educated than anyone you might encounter trying to sell you one of the tests.

But my friend said the test worked for them?

The results of these tests almost inevitably involve an individual cutting out a large group of foods from their diet based on the “test results”.

Within that group of foods, there is certainly a possibility that one or more potential problem foods was removed, especially if an individual is intolerant to multiple foods/food components.

The only problem is that numerous other healthy, well-tolerated foods would also have been removed as part of that process.

And you won’t have any idea which is which.

This is a big problem.

So how do you deal with food intolerance then?

Dealing with food intolerance can be a very complex issue, depending on the individual.

At the end of the day, every single gut is unique and there is no one size fits all solution.

I suggest starting with more diligent observation of the foods you are eating and the symptoms that follow, keeping a food & symptom diary is a preliminary step to help you better understand how your body responds to certain foods.

In more complex cases, simply keeping a  food & symptom diary may be insufficient to help you suss out the culprit foods.

If you fall into this category your best course of action is to seek guidance from your doctor (especially if an allergy is suspected) and to pursue assistance from a registered dietitian who has a practice built on treating digestive health concerns.

There are dietary patterns that currently exist, such as the Low FODMAP diet, with the goal of helping individuals with complex digestive health concerns address their symptoms and better understand the foods they can tolerate.

There are also likely a variety of other strategies and approaches that practitioners who specialize in digestive health are employing.

None of these approaches are a quick fix.

They require time, diligence and, in most cases, professional guidance to implement safely and properly.

Be very careful when removing multiple foods or food groups from your diet without due cause or professional guidance because this opens you up to serious health issues owing to a nutritionally inadequate diet.

Food intolerance is a complex health issue that, as annoying as it may be, requires a solution with the complexity beyond just a simple blood test.