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How to Test for a Leaky Gut (& Why It Might Not Be Worth It)

Written by Dr. Michael Ruscio, DC on February 6, 2025

Written by Dr. Michael Ruscio, DC on February 6, 2025 — Reviewed by Kellie Blake

• Leaky Gut 101|
• Before You Test|
• Stool Tests|
• Zonulin Tests|
• Antibody Tests|
• Lactulose:Mannitol Tests|
• Clinical Perspective|
• Leaky Gut Treatments|

If you’re concerned you might have a leaky gut, aka increased intestinal permeability, you might be considering getting tested.

However, blood, stool, and urine tests can be expensive and complex, so it’s important to understand what insights they truly offer. 

Let’s take a closer look into how to test for leaky gut, which tests are most valuable, and how you can improve your symptoms—whether or not you decide to test.

Leaky Gut 101

A healthy intestinal barrier helps prevent microbes, undigested food particles, and other harmful substances from moving out of your digestive system and into the bloodstream. 

However, if the intestinal lining loses its barrier function, unwanted substances leak through it into areas of the body where they don’t belong 1.

Symptoms linked to leaky gut include: 

• General gastrointestinal tract symptoms, such as bloating, diarrhea, constipation, and abdominal pain
• Indigestion 2
• Depression 3
• Fatigue 4
• Joint pain 5
• Poor sleep 6 7
• Weight gain 8
• Food allergies 9

Research suggests that 36–88% of people with chronic symptoms may have a leaky gut lining 10. Such intestinal permeability may also contribute to health conditions, including inflammatory bowel disease (IBD), liver conditions, and type-1 diabetes 1.

How to Test for Leaky Gut: 4 Methods

It’s important to understand that all guts are naturally “leaky” or semipermeable to some extent. A little bit of leakiness is what allows the intestines to absorb and deliver water and nutrients from food.

Therefore, leaky gut tests try to estimate whether your gut is more permeable than average, which can be somewhat subjective. 

If you’re set on testing, it’s best to work with a healthcare practitioner who thoroughly understands your symptoms. These signals are required for a more accurate interpretation of the results.

With that in mind, let’s explore the four main types of testing and how useful they are.

1. Stool Tests

Stool tests look at the makeup of the microbiome and measure these indirect markers of leaky gut:

• Dysbiosis (disrupted gut microbes)
• Infections or parasites 
• Candida yeast
• Biomarkers of immune system activity, like calprotectin, lactoferrin, and secretory IgA (immunoglobulin A)

How Useful Are Stool Tests?

Not very. Stool tests only identify the microbiome and immune abnormalities that can happen at the same time as leaky gut—not the gut permeability itself.

Microbiome testing also has inconsistent results that often bear little relation to a client’s symptoms.

For example, one of our clinicians (a healthy male with no symptoms) took two stool tests, just one week apart.

The first test showed substantial dysbiosis and inflammation. The second test showed far less dysbiosis and no inflammation. In a nutshell, the results didn’t agree at all.

If your practitioner recommends stool testing for leaky gut, be sure to ask how they plan to interpret the results and what specific insights you can expect to gain.

2. Zonulin Tests

Zonulin is a protein that affects how tight the junctions are between intestinal cells. 

Higher zonulin levels can indicate that the tight junctions are loosened, which means unwanted substances can leak through. Zonulin can be measured in the stool or blood.

How Useful Are Zonulin Tests?

Reasonably useful. Zonulin measured in the blood (rather than stool) correlates with a wide variety of symptoms and is often elevated in many chronic conditions related to leaky gut 11 12 13. 

However, a problem with zonulin testing is the lack of a standardized “normal” range, which makes it hard to know what levels are and aren’t problematic 14 15.

Additionally, responses to treatment based on zonulin levels can be inconsistent. For example, a person might see a significant drop in zonulin but only a modest improvement in symptoms, or vice versa.

If you choose to do zonulin testing, remember that your symptoms are more important than focusing solely on lab values.

3. Antibody Tests

Antibody tests search the blood for antibodies trying to fight our own gut barrier proteins (like occludin and zonulin). These tests can also detect antibodies against bacterial toxins called lipopolysaccharide, or LPS. 

The theory is that if the gut barrier is compromised, gut barrier proteins and LPS may leak into the bloodstream. Because they don’t belong there, they trigger an immune response that elevates antibody levels.

How Useful Are Antibody Tests?

Hardly at all. A key issue with antibody testing for leaky gut is cross-reactivity. This is when antibodies react to multiple substances (antigens), not just the gut barrier proteins and LPS related to gut permeability. As a result, antibody tests can produce unreliable results.

Antibodies may also remain high for long periods, blurring whether a leaky gut is currently present.

Not only that, but gut antibodies don’t correlate well with symptoms. A 2022 study tested volunteers for leaky gut antibodies and found no difference in the levels of antibodies between those with and without symptoms 16.

4. Lactulose-to-Mannitol Ratio Tests

Lactulose-to-mannitol ratio tests involve swallowing the sugar molecules lactulose and mannitol after an overnight fast. Urine samples are then collected over the next 5–6 hours and a lab measures the lactulose and mannitol in these samples. 

Mannitol is a small molecule that passes easily through the wall of the intestines into the bloodstream and eventually shows up in the urine. Lactulose is a larger molecule that a healthy gut should absorb only a little, which means it should stay inside the gut and not appear in the urine. 

If high levels of lactulose appear in the urine compared to mannitol, it suggests a leaky gut. In other words, bigger-than-normal gaps in the intestinal barrier have allowed larger molecules to pass into the bloodstream and exit through the urine.

How Useful Are Lactulose to Mannitol Ratio Tests?

Fairly useful. A meta-analysis (high-quality study of studies) found that lactulose-mannitol ratio tests can distinguish people with gut conditions like celiac disease or inflammatory bowel disease from healthy individuals. Higher lactulose-to-mannitol ratios (a sign of leaky gut) also went hand-in-hand with higher disease activity 17.

On the flip side, lactulose-mannitol ratio results tend to improve (urine lactulose levels go down) after treatments that heal a leaky gut 18 19 20.

However, there are drawbacks to the lactulose-mannitol ratio. There’s no widely accepted normal range for the test, and the testing process is time consuming 17. 

Additionally, many tests use 12-carbon mannitol, which is also found in foods and cosmetics and can thus lead to artificially high results. Researchers are working on validating a more reliable test using 13-carbon mannitol.

Despite these challenges, a lactulose-to-mannitol ratio test may be valuable if interpreted in the context of your symptoms by a knowledgeable doctor who knows your health history.

Why I Rarely Use Leaky Gut Tests as a Clinician

The lactulose-to-mannitol ratio and blood zonulin tests are the most useful for detecting leaky gut, but no test is perfect.

In my clinical practice, a diverse range of gastrointestinal and cognitive symptoms are reliable clues that someone’s gut is leaky. Given how often I encounter and treat these symptoms of a leaky gut, I rarely use leaky gut testing. Usually, it just adds extra cost to my clients without clarifying my diagnosis or changing my treatment approach. 

Fundamentally, if a client presents symptoms that fit the profile of a leaky gut, it’s reasonable to assume they have it. As the saying goes, “If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.”

Leaky gut often co-occurs with gut microbiome imbalances such as dysbiosis, Candida overgrowth, and small intestinal bacterial overgrowth (SIBO). If a client has IBS-type symptoms—like gas, bloating, abdominal discomfort, food sensitivities, brain fog, and mood changes—we can safely infer they have gut disturbances without trying to pinpoint the exact issue.

These symptoms typically respond well to gut-supportive dietary and lifestyle changes. If they don’t improve after 2–3 months, we can then dig deeper to check for other underlying conditions.

If you and your practitioner decide to pursue testing for leaky gut, remember that your symptoms are more important than chasing lab values. If your test results haven’t improved much after treatment but you’re feeling significantly better, it’s wise to trust your symptoms (or lack thereof) over the numbers.

Leaky Gut Treatments

The only known cure for a leaky gut is to treat the poor gut health and gut dysbiosis (imbalanced gut microbes) that underlie it. This can be done through a combination of diet and lifestyle shifts. 

Healthy Dietary Changes

First things first: Cutting down on processed foods 21 and alcohol 22 and adding more whole, anti-inflammatory foods to your diet is the best place to start. 

Certain whole foods, or components of them, can be especially great for healing a leaky gut, as long as your gut can tolerate them. These include:

• Polyphenols (e.g., in apples, berries, onions, broccoli, green tea, and spices) 23
• Dark chocolate 24
• Fiber 25
• Fermented foods, like kefir 26

Keeping fat intake in check can also be helpful 27.

While these general healthy eating guidelines are a good start, there are also specific diets that can help.

Anti-Inflammatory Diets 

The following three anti-inflammatory diets have research showing that they may improve a leaky gut:

• Mediterranean diet 28
• Low-FODMAP diet 20
• Gluten-free diet 29

Mediterranean diets are rich in oily fish (a great source of anti-inflammatory omega-3 fatty acids), berries, and vegetables. A whole-food Mediterranean diet can help heal a damaged gut and offers many general health benefits, like lower cardiovascular risk.

A low-FODMAP diet can be very effective for those whose IBS-like symptoms are particularly troublesome and seem to be triggered by a wider range of foods. 

A gluten-free diet can help those who find that gluten aggravates or contributes to their symptoms. In this case, a Mediterranean or low-FODMAP diet can work well when gluten-containing grains like wheat, rye, and barley are swapped for alternatives like buckwheat or quinoa.

I’d recommend working with a doctor or dietitian to find the diet that works best for you, especially if choosing an elimination diet like low FODMAP. Their expertise is especially helpful when it comes to reintroducing foods once your symptoms have improved.

Elemental Diet

For clients with strong symptoms who need a gut reset, an elemental diet—a predigested, liquid diet—can work wonders.

Elemental diets may help to reduce inflammation in the gut and heal leaky areas 30 31 32, clearing the slate for a healthy diet to build a balanced gut microbiome.

Lifestyle Shifts

What we eat plays a major role in our gut health, but it can only go so far if the way we live doesn’t support our immune system and gut function. As my clients incorporate healthy dietary changes, I also coach them to dial in their daily movement, sleep habits, and stress management techniques. Sometimes, supplements can be helpful too.

Stress Management

High stress levels may contribute to a leaky gut 33 34, while reducing stress can lower inflammation 35. 

Incorporating stress management into your routine is therefore crucial. My clients often benefit from:

• Daily meditation
• Spending time in nature, ideally at least two hours every week
• Talking therapies like cognitive behavioral therapy (CBT)

Exercise

Staying active isn’t just great for your overall fitness—it can do wonders for your gut health, too. Activities like running, cycling, and gym workouts can boost gut health by 36:

• Helping the stomach empty faster
• Enhancing gut motility (how food moves through the GI tract)
• Optimizing the balance of the gut microbiota  

The ideal is to do moderate- to vigorous-intensity workouts—whatever feels best—3 to 5 times a week. However, I advise my clients to keep high-intensity workouts to under one hour. Sessions longer than 60 minutes of vigorous exercise may actually worsen a leaky gut 36.

Better Sleep

Research has shown that low-quality sleep may contribute to a leaky gut 37, so getting good sleep regularly is an important step in healing it. You’ll already be on the path to better sleep by managing stress and exercising regularly. To further improve sleep:

• Maintain a consistent sleep and wake routine.
• Avoid eating or exercising too late in the day.
• Avoid caffeine 12 hours before bedtime 38.
• Limit blue light exposure 1–2 hours before bed.

Supplements

Probiotics are my top supplement for helping heal a leaky gut. Research shows they can reduce inflammatory and leaky gut markers 18 and digestive symptoms 39. 

I advise my clients to try a complete triple therapy approach to probiotic supplementation because it’s usually what works best for symptoms.

The three probiotics we use are:

• A Lactobacillus/Bifidobacterium blend
• A soil-based probiotic
• The healthy yeast Saccharomyces boulardii

If people have a particularly sensitive gut, I may introduce these one at a time starting with the Lactobacillus/Bifidobacterium blend, which is an effective base probiotic. 

Once the foundations of diet, lifestyle, and probiotics are secure, most of my clients don’t need anything else to feel better. But for those who still haven’t made satisfying progress, we’ll often do a trial of one or more other leaky gut supplements. 

Shown in studies to improve leaky gut markers, inflammation, and symptoms, these include:   

• Bovine colostrum 40
• Immunoglobulins 41
• Glutamine 19

Think You Need a Leaky Gut Test? Think Again.

In summary, while testing for a leaky gut can provide some insights, it often isn’t necessary to determine whether gut permeability is contributing to symptoms. 

Many tests are costly, can be inconsistent, and may not influence the treatment plan.

Instead, focusing on diet, lifestyle, and gut-supportive supplements is often the most effective approach. And trusting the body’s response to these interventions is more important than chasing perfect lab values.

If symptoms don’t improve after a few months, that’s the time to reassess and consider deeper testing or treatments. If you’d like help from one of our experienced gut health clinicians at the Ruscio Institute for Functional Health, just reach out.

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