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

Written by Dr. Michael Ruscio, DC on November 10, 2025

Written by Dr. Michael Ruscio, DC on November 10, 2025 — Reviewed by Hannah Wright

• Understanding Leaky Gut|
• 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 at 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.

Understanding Leaky Gut 

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 can leak through it into areas of the body where they don’t belong 1 and may cause widespread inflammation. This increased intestinal permeability is often referred to as leaky gut.  

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
• Weight gain 7
• Food allergies 8

Research suggests that 36–88% of people with chronic symptoms may have a leaky gut lining 9. Such intestinal permeability may also co–occur with or be related to health conditions, including:

• Irritable bowel syndrome (IBS) 10 11
• Inflammatory bowel disease (IBD) 1
• Small intestinal bacterial overgrowth (SIBO) 12
• Dysbiosis (imbalanced gut microbes) 13
• Mild cognitive impairment and Alzheimer’s disease 14
• Rheumatoid arthritis 5

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 decide to get tested, work with a practitioner who really understands your symptoms—they’re key to interpreting the results accurately.

With that in mind, let’s explore the four main types of leaky gut 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 from bacteria 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 a lot of 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 created in the cells of the small intestine and liver—it affects how tight the junctions (bonds) are between intestinal cells. Higher zonulin levels can indicate loosening, 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 15 16. 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 17 18.

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 the body’s gut barrier proteins (like occludin and zonulin). These tests can also detect antibodies against bacterial toxins called lipopolysaccharides, 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. One study tested volunteers for leaky gut antibodies and found no difference in the levels of antibodies between those with and without symptoms 19.

4. Lactulose–Mannitol Ratio Tests

Lactulose–mannitol ratio tests, also called dual sugar 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 more lactulose than mannitol appears in the urine, it suggests a leaky gut. In other words, bigger-than-normal gaps in the intestinal barrier have allowed too many of the larger lactulose molecules to pass into the bloodstream and exit through the urine.

How Useful Are Lactulose–Mannitol Ratio Tests?

Fairly useful. A meta-analysis (high-quality study of studies) found that lactulose–mannitol ratio tests distinguished people with gut conditions like celiac disease or inflammatory bowel disease from healthy individuals 20. Higher lactulose–mannitol ratios (a sign of leaky gut) also went hand-in-hand with higher disease activity.  

Lactulose–mannitol ratio results tend to improve (urine lactulose levels go down) after treatments that help heal a leaky gut 21 22 23.

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 20. Also, many tests use 12-carbon mannitol, which is also found in foods and cosmetics and can 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 healthcare provider who knows your health history.

Other Leaky Gut Syndrome Tests

The following biomarkers could theoretically help detect leaky gut, so we’re keeping an eye on them:

• Lipopolysaccharide (LPS)—bacterial fragments that can leak into the bloodstream; higher levels are linked to increased zonulin, a protein that loosens the gut barrier 24. 
• Lipopolysaccharide binding protein (LBP)—a blood marker that rises when LPS levels are high; it often lines up with results from the lactulose–mannitol test 25. 
• Intestinal fatty acid binding protein (I-FABP)—a marker of gut cell turnover; high levels may mean intestinal cells are being damaged or replaced too quickly 26 27.
• Citrulline—an amino acid made by intestinal cells; lower levels can suggest reduced gut function or increased permeability (“leaky gut”) 26.
• Claudin-3 in urine—a protein that may show up in urine when the gut barrier is weakened or damaged 27.

None of these biomarker tests has been validated for use in clinical practice 28.

Bottom line: The lactulose–mannitol ratio and blood zonulin tests are the most useful for detecting leaky gut, but no test is perfect.

Why I Rarely Use Leaky Gut Tests as a Clinician

In my clinic, a wide range of digestive and cognitive symptoms reliably point to leaky gut. Because these patterns are so recognizable, I rarely order specific tests because they add cost without changing how I diagnose or treat. If someone has the typical signs, it’s reasonable to assume that a leaky gut is part of the picture.

Leaky gut often appears alongside gut imbalances like dysbiosis, Candida overgrowth, or SIBO. When clients report IBS-type symptoms—gas, bloating, abdominal pain, food sensitivities, brain fog, or mood changes—it’s safe to assume some gut dysfunction is present, even without pinpointing the exact cause.

Most people improve with a gut-supportive diet and lifestyle changes. If symptoms don’t ease up within 2–3 months, that’s the time to look deeper for other issues. And for those who choose to test, remember that your symptoms matter more than lab results—how you feel is the best indicator of progress.

Healing Without the Need for a Test: Treatment in Action

Adrian had been struggling with chronic brain fog, joint pain, and fatigue for several years. Despite visiting a variety of healthcare providers—both conventional and naturopathic—he saw some improvement but never truly felt well. It wasn’t until he followed the gut-healing plan from Healthy Gut, Healthy You that he finally experienced lasting relief.

Adrian was never formally diagnosed with leaky gut, but his symptoms clearly pointed to it. The key is, he didn’t need a test to get better—by improving his diet and lifestyle to support gut health, his symptoms greatly improved.

Leaky Gut Treatments

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

Healthy Dietary Changes

First things first: Cut down on processed foods 29 and alcohol 30, and add more whole, anti-inflammatory foods to your diet. 

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 (like in apples, berries, onions, broccoli, green tea, and spices) 31
• Dark chocolate (also rich in polyphenols) 32
• Fiber 33
• Kefir (fermented milk drink) 34

Keeping fat intake in check can also be helpful 35.

These general healthy eating guidelines are a good start, and the following diets can take things to the next level.

Anti-Inflammatory Diets 

These anti-inflammatory diets have research showing that they may help heal a leaky gut:

• Mediterranean diet 36
• Low-FODMAP diet 23
• Gluten-free diet 37

A Mediterranean diet is 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 effective for people whose IBS-like symptoms are very troublesome and seem to be triggered by a wider range of foods. 

A gluten-free diet can help people who find that gluten aggravates or contributes to their symptoms. In these cases, 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 registered 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 reduce inflammation in the gut and heal leaky areas 38 39 40, paving the way for a healthy diet to build a balanced gut microbiome.

Lifestyle Shifts

A healthy diet is key for gut health, but it works best when paired with healthy habits. Along with nutrition changes, I help clients improve their stress management, daily movement, and sleep quality, and sometimes add supplements for extra support.

Stress Management

High stress levels may contribute to a leaky gut 41 42, but reducing stress can reduce inflammation 43. 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
• Talk 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 may boost gut health by 44:

• 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 44.

Better Sleep

Research has shown that low-quality sleep may contribute to a leaky gut 45, so getting good sleep regularly is an important step toward healing it. To further improve sleep:

• Maintain a consistent sleep and wake routine.
• Avoid eating or exercising too late in the day.
• Avoid caffeine at least 12 hours before bedtime 46.
• 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 21 and digestive symptoms 47. 

I advise my clients to try our triple therapy approach to probiotics because it’s usually what works best for leaky gut symptoms.

The three probiotics we use are:

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

For people with sensitive digestion, I start slowly—usually introducing probiotics one at a time, beginning with a Lactobacillus/Bifidobacterium blend as the foundation. Once the right diet, a balanced lifestyle, and probiotics are in place, most people feel better. 

But for those who don’t, we may add other supplements shown in studies to improve leaky gut, inflammation, and related symptoms, such as:  

• Bovine colostrum 48
• Immunoglobulins 49
• Glutamine 22

Think You Need a Leaky Gut Test? Go Ahead and Think Again.

Testing for a leaky gut can provide some insights, but it often isn’t necessary to determine whether gut permeability is contributing to symptoms. 

Many tests are costly, unreliable, and rarely change our treatment plan. Focusing on an anti-inflammatory diet and lifestyle, along with gut-supportive supplements, is usually more effective—and the body’s response matters more than perfect lab numbers.

If symptoms haven’t improved after a few months, that’s the time to reassess and consider more targeted testing or treatments. If you’d like support, our gut health clinicians at the Ruscio Institute for Functional Health can help.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.