Mycotoxin Testing: The Complete Guide
How to Test for Mould Illness — What Works, What Doesn't, and What to Do Next
If you suspect that mould exposure is affecting your health, one of the first questions you'll ask is: can I actually test for this? The answer is yes — but with important caveats. Mycotoxin testing is one of the most valuable tools available for investigating mould-related illness, yet it is also one of the most misunderstood and misinterpreted.
In this guide, we walk you through what mycotoxins are, why they matter, how we test for them, which laboratories offer reliable panels, what additional tests can provide critical supporting information, and — crucially — the significant limitations you need to understand before you draw any conclusions from your results.
This is not a simple topic. That is precisely why knowing how to interpret these results, and having the right clinical support, makes all the difference between clarity and confusion.
What Are Mycotoxins?
Mycotoxins are toxic secondary metabolites produced by certain species of mould (fungi). They are not the mould itself, but rather the chemical compounds that moulds release — often as a defence mechanism or as a byproduct of their growth. The word comes from the Greek 'mykes' (fungus) and the Latin 'toxicum' (poison).
Not all moulds produce mycotoxins, and not all mycotoxin-producing moulds do so under every condition. Mycotoxin production tends to be triggered by specific environmental conditions — particularly moisture, temperature, and the availability of certain substrates (the materials on which mould grows). This is one reason why water-damaged buildings are such a significant concern.
Mycotoxins and Human Health
Mycotoxins are among the most potent naturally occurring toxins on the planet. They have been studied in agricultural and food safety contexts for decades, largely because of their contamination of grain crops. More recently, clinical and environmental medicine has begun to take seriously their role in chronic illness arising from indoor mould exposure.
Once inside the body, mycotoxins can exert a range of harmful effects, including:
Disrupting mitochondrial function and cellular energy production
Triggering chronic inflammation and immune dysregulation
Damaging the gut lining and disrupting the microbiome
Impairing detoxification pathways, particularly glutathione-dependent processes
Acting as potent immunosuppressants, leaving the body vulnerable to secondary infections
Crossing the blood-brain barrier and driving neurological symptoms
Disrupting hormonal signalling and endocrine function
The Most Clinically Relevant Mycotoxins
There are hundreds of known mycotoxins, but a handful appear most frequently in the context of indoor mould illness:
Ochratoxin A (OTA)
Produced primarily by Aspergillus and Penicillium species, ochratoxin A is one of the most well-studied mycotoxins in clinical practice. It is a potent nephrotoxin (toxic to the kidneys), immunosuppressant, and probable human carcinogen. OTA is also highly persistent in the body due to its enterohepatic recirculation — it can be reabsorbed from the gut rather than efficiently eliminated, making it particularly problematic for individuals with impaired detoxification.
Trichothecenes
This is a large group of mycotoxins produced predominantly by Stachybotrys chartarum — the infamous 'black mould' — as well as Fusarium species. Trichothecenes are among the most potent inhibitors of protein synthesis known, and they have been extensively studied in the context of both food contamination and chemical warfare. In clinical practice, they are associated with severe neurological symptoms, immune dysfunction, and chronic fatigue.
Aflatoxins
Produced by Aspergillus flavus and Aspergillus parasiticus, aflatoxins are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC). They are perhaps the most well-known mycotoxins in the world, largely due to their impact on food crops. In the context of mould illness, aflatoxin B1 is the most commonly measured and the most biologically active.
Gliotoxin
Produced by Aspergillus fumigatus, gliotoxin is an immunosuppressive mycotoxin of particular significance for individuals with Candida or Aspergillus colonisation in the gut or sinuses. Its role in chronic fungal colonisation is an emerging area of clinical interest.
Zearalenone and Fumonisins
Produced by Fusarium species, zearalenone is an oestrogen-like compound that can disrupt hormonal balance, while fumonisins interfere with sphingolipid metabolism and have been associated with oesophageal cancer and neural tube defects in areas of high dietary exposure.
How Do We Test for Mycotoxins?
There are two primary biological matrices used for mycotoxin testing in clinical practice: urine and serum (blood). Each has its strengths and limitations, and understanding the difference is essential for accurate interpretation.
Urine Mycotoxin Testing
Urine mycotoxin testing is the most widely used method in functional and integrative medicine. The underlying principle is straightforward: mycotoxins that have been metabolised by the body are excreted through the kidneys into the urine, where they can be detected and quantified.
Urine testing is particularly useful because it reflects current mycotoxin burden — it captures what the body is actively processing and eliminating. It is non-invasive, relatively affordable, and can detect a broad spectrum of mycotoxins in a single sample.
Provoked vs. Unprovoked Urine Testing
One important clinical consideration is whether to collect a 'first morning' urine sample (unprovoked) or to use a glutathione push protocol before sample collection (provoked). Glutathione mobilises stored mycotoxins from tissues into circulation, potentially increasing urinary excretion and improving detection sensitivity. Provoked testing can be particularly valuable for patients who are poor detoxifiers or have been out of a mould-toxic environment for some time.
This distinction matters considerably for result interpretation — provoked and unprovoked samples should not be compared directly — and is one of many nuances that an experienced practitioner needs to navigate carefully.
Serum (Blood) Mycotoxin and Antibody Testing
Blood-based testing takes two distinct approaches: direct measurement of mycotoxins in serum, and measurement of antibodies the immune system has produced in response to mycotoxin exposure.
Serum Mycotoxin Levels
Direct serum mycotoxin testing can detect mycotoxins circulating in the bloodstream. This can be useful in acute or ongoing high-level exposures, but mycotoxins are rapidly distributed into tissues and may not remain detectable in serum for extended periods. This makes serum less sensitive than urine for detecting chronic low-level exposure.
Mycotoxin Antibody Testing
Antibody testing (IgG, IgA, IgM) measures the immune system's response to mycotoxin exposure rather than the mycotoxins themselves. This is a fundamentally different type of information: it tells us that the immune system has mounted a response to one or more mycotoxins, suggesting past or ongoing exposure.
Antibody testing has the advantage of being less dependent on the timing of sample collection relative to current exposure — antibodies persist in circulation longer than mycotoxins themselves. It can therefore be particularly useful for individuals who have left a mould-toxic environment but remain symptomatic.
Which Laboratories Offer Mycotoxin Testing?
Several specialist laboratories now offer comprehensive mycotoxin panels. Each has different methodologies, analyte panels, reference ranges, and clinical support materials. Understanding the differences is important — results from one laboratory are not directly comparable to another.
Urine Mycotoxin Panels
Mosaic Diagnostics (formerly Great Plains Laboratory)
Mosaic offers one of the most established urine mycotoxin panels available, measuring a broad range of mycotoxins including OTA, aflatoxins, trichothecenes, gliotoxin, zearalenone, fumonisins, and others. Their MycoTOX Profile is widely used in functional medicine practice and is supported by extensive published reference data. The test uses liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is considered the gold standard analytical method for mycotoxin detection.
Vibrant America / Vibrant Wellness
Vibrant America offers a mycotoxin panel using ELISA (enzyme-linked immunosorbent assay) technology. Their panel covers a wide range of mycotoxins and includes both urine and serum options. Vibrant's platform is well regarded for its accessibility and the breadth of analytes covered, though methodological differences between ELISA and LC-MS/MS panels are an important consideration when comparing results across laboratories.
RealTime Laboratories
RealTime Labs uses an ELISA-based methodology and offers testing for trichothecenes, aflatoxins, and ochratoxins in urine. They were among the earliest laboratories to offer mycotoxin urine testing in a clinical context and have an established track record in environmental medicine. RealTime also offers ERMI (Environmental Relative Mouldiness Index) testing for the home environment — pairing clinical and environmental testing is always best practice.
Blood Antibody Testing
MyMycoLab
MyMycoLab offers a distinctive approach to mould illness testing through antibody measurement. Their panel measures IgG, IgA, and IgM antibody responses to a panel of mycotoxins in serum, providing insight into the immune system's historical and ongoing reactivity. This makes MyMycoLab a particularly complementary test to urine mycotoxin panels — urine reflects current excretion while antibodies reflect immune exposure history. Combining the two approaches can provide a more complete picture of both the body's mycotoxin burden and its immune response to that exposure.
A Note on Methodology: LC-MS/MS vs. ELISA
Both LC-MS/MS and ELISA are validated analytical methods, but they work differently and have different sensitivity and specificity profiles for different mycotoxins.
LC-MS/MS (Mosaic/Great Plains) is generally considered the more sensitive and specific method, particularly for lower-level exposures.
ELISA (Vibrant, RealTime) is a well-established immunological method that can perform excellently for certain analytes.
Importantly, results from different methodologies cannot be directly compared. Always work with a practitioner who understands the specific platform your results come from.
Companion Tests That Provide Critical Context
Mycotoxin testing alone rarely tells the full story. Several additional investigations can provide essential supporting information — both to contextualise mycotoxin results and to guide a clinical recovery protocol.
Organic Acids Testing (OAT)
Organic acids testing is a urine-based panel that measures a broad range of metabolic byproducts, reflecting the functional status of multiple biochemical pathways. In the context of mould illness, several organic acid markers are particularly relevant:
Glutathione status markers: Pyroglutamate (5-oxoproline) is a marker of glutathione depletion. Glutathione is the body's master antioxidant and a critical component of the detoxification pathway for many mycotoxins. An elevated pyroglutamate indicates the body is under significant oxidative stress and struggling to regenerate glutathione — a finding that has important implications for both interpretation of mycotoxin results and treatment planning.
Oxalate markers: Mycotoxin exposure — particularly from Aspergillus species — can drive elevated oxalate production. High urinary oxalates can contribute to pain syndromes, kidney stress, and mitochondrial dysfunction. This is a commonly overlooked finding in mould illness.
Markers of fungal/yeast overgrowth: The OAT includes markers such as arabinose, citramalic acid, and tartaric acid that can indicate intestinal yeast or fungal overgrowth — a common sequela of mycotoxin exposure and the immune dysregulation it produces.
Mitochondrial function markers: Markers such as succinic acid, fumaric acid, and malic acid reflect mitochondrial health. Given that many mycotoxins directly impair mitochondrial function, these markers can help quantify the degree of cellular energy impairment.
In our experience, organic acids testing is one of the most valuable companion tests to mycotoxin panels. It provides metabolic depth that mycotoxin testing alone cannot offer.
Comprehensive Blood Panel
A well-constructed blood panel can reveal systemic patterns consistent with mycotoxin exposure and help rule out other contributing conditions. Key markers to consider include:
Inflammatory markers (CRP, ESR, ferritin) — chronic low-grade inflammation is a hallmark of mould illness
Immune panel — patterns such as lymphopenia, elevated eosinophils, or specific immunoglobulin abnormalities can be consistent with mould-related immune dysregulation
Liver function tests — given the liver's central role in mycotoxin detoxification, hepatic stress markers are important to monitor
Kidney function markers — particularly for ochratoxin A exposure, given its well-documented nephrotoxicity
Thyroid function — mycotoxins can disrupt thyroid signalling; subclinical thyroid dysfunction is commonly seen in mould illness
Full blood count — to identify anaemia, immune cell abnormalities, or thrombocytopenia
HLA-DR Genetic Testing
Approximately 24% of the population carries HLA-DR genetic variants that impair the immune system's ability to produce antibodies against certain biotoxins, including mycotoxins. These individuals — often referred to as 'non-responders' or those with CIRS (Chronic Inflammatory Response Syndrome) susceptibility — are disproportionately affected by mould illness and may have dramatically more severe symptoms at lower levels of exposure than the general population.
HLA-DR typing is a simple blood or saliva test that can provide important context for why some individuals remain acutely ill despite leaving a mould-toxic environment and beginning treatment.
Stool Microbiome Analysis
The gut microbiome is both a target of mycotoxin damage and a key modulator of how effectively the body processes and eliminates mycotoxins. Several mycotoxins — including OTA and zearalenone — undergo enterohepatic recirculation, meaning they can be reabsorbed from the gut rather than excreted. A healthy, diverse microbiome with robust bile salt hydrolase activity (produced by certain Lactobacillus and Bifidobacterium species) is protective against this recirculation.
Comprehensive stool analysis can also identify fungal overgrowth, dysbiosis patterns, and intestinal inflammation that commonly accompany mould illness, and that may need to be addressed as part of a comprehensive recovery protocol.
Visual Contrast Sensitivity (VCS) Testing
The VCS test is a simple, inexpensive visual test that measures the ability to distinguish contrast — a neurological function impaired by biotoxins. It is not specific to mycotoxins but is widely used as a screening tool and monitoring tool in the context of biotoxin illness. A positive VCS result (impaired contrast sensitivity) in the presence of a relevant exposure history adds meaningful supporting evidence to a clinical picture of mould illness. It can also be a useful monitoring tool to track recovery over time.
The Limitations of Mycotoxin Testing: What You Need to Know
This is perhaps the most important section of this guide. Mycotoxin testing is a genuinely valuable clinical tool — but it is far from straightforward, and results that are misunderstood can lead to both false reassurance and unnecessary alarm.
A Negative Result Does Not Mean You Have Not Been Exposed
This is the single most important limitation to understand. A negative mycotoxin test does not rule out mould illness. There are several reasons why this is the case:
Mycotoxins may be sequestered in tissues rather than actively circulating or being excreted. A urine test only captures what the body is currently eliminating — if detoxification pathways are impaired, excretion may be minimal even in the presence of a significant body burden.
Timing matters. If you have not been recently exposed or are no longer in a mould-toxic environment, urinary mycotoxin levels may have normalised even if significant damage has occurred.
The panel may not cover all relevant mycotoxins. No laboratory tests for every known mycotoxin. If the specific mycotoxin(s) driving your illness are not on the panel, they will not be detected.
Individual variation in excretion rates is substantial. Genetic variants in detoxification enzymes (particularly in the glutathione-S-transferase family) mean that some individuals excrete mycotoxins efficiently while others retain them in tissues.
A Positive Result Requires Expert Interpretation
A positive mycotoxin test is clinically significant — but the question of what to do with that information is not simple. Key interpretive challenges include:
Reference ranges vary between laboratories and methodologies, and are not universally agreed upon. A value flagged as elevated on one platform may sit within the reference range on another.
Dietary exposure is a confounder. Many mycotoxins — particularly OTA, aflatoxins, and zearalenone — are present in food (grains, dried fruits, coffee, wine, corn-based products). A positive result may reflect dietary exposure rather than, or in addition to, environmental exposure from a water-damaged building. Distinguishing between the two requires clinical context.
The degree of elevation, the pattern of mycotoxins detected, and the clinical presentation must all be integrated. A mildly elevated OTA in a patient who drinks wine daily and lives in a dry, well-maintained home tells a different story from the same finding in a patient with severe fatigue, brain fog, and a history of documented water damage.
Serial testing — measuring levels over time in response to interventions — is often more informative than a single snapshot.
The Environmental Picture Must Be Investigated
A positive mycotoxin test is a clinical finding that demands an environmental investigation, not just a clinical protocol. If the source of exposure has not been identified and remediated, no treatment protocol will produce lasting results. Air and surface sampling, ERMI testing, and in some cases expert environmental assessment of the building are essential components of a comprehensive mould illness workup.
Mould Illness Is a Clinical Diagnosis
Ultimately, a mycotoxin test is a piece of evidence — not a diagnosis. Mould illness (or CIRS — Chronic Inflammatory Response Syndrome to biotoxins) is a clinical diagnosis that integrates symptom presentation, exposure history, laboratory findings, genetic susceptibility, and response to treatment. No single test confirms or excludes the diagnosis. This is why working with a practitioner who has deep experience in this area is not a luxury — it is a necessity.
So, What Should You Do?
If you suspect mould illness, here is the foundational framework we work from:
Start with a thorough exposure history — what buildings have you lived or worked in? Have you noticed visible mould, water damage, a musty smell, or worsening of symptoms in certain environments?
Consider a comprehensive mycotoxin test — both urine (Mosaic, Vibrant, or RealTime) and blood antibody testing (MyMycoLab) together provide a more complete picture than either alone.
Pair mycotoxin testing with an organic acids panel to assess glutathione status, oxalate burden, and fungal overgrowth markers.
Include relevant blood markers — inflammatory markers, immune panel, liver and kidney function, thyroid, and full blood count at minimum.
Investigate your environment — testing your body without testing your home is only half the picture.
Work with an experienced practitioner to interpret results in the context of your full clinical picture, genetic susceptibility, and exposure history.
Ready to Go Deeper? The Mould Mastery Course
Navigating mould illness — from testing and interpretation to treatment and recovery — is one of the most complex areas of functional and environmental medicine.
The Mould Mastery Course is a comprehensive, evidence-based programme designed to walk you through every stage of the journey: understanding your results, identifying your exposures, rebuilding your detoxification capacity, restoring your immune system, and recovering your health.
Whether you are just beginning to investigate mould as a possible cause of your symptoms, or you have a stack of test results and no clear path forward, the course gives you the clinical framework — and the practical roadmap — that you need.
Prefer to work directly with us? We offer 1-2-1 consultations for individuals who would benefit from personalised clinical support alongside or instead of the course.
Visit mouldmastery.com to learn more.
A Final Word
Mould illness is real, it is measurable, and it is treatable. But it is also complex, frequently misdiagnosed, and all too often dismissed. The individuals who come to us have usually been unwell for months or years, have seen multiple clinicians without answers, and are rightly sceptical of easy solutions.
What we offer is clinical rigour, genuine expertise, and a deep respect for the complexity of what you are going through. Mycotoxin testing is one important tool in a comprehensive investigation — and we hope this guide has helped you understand both its value and its limits.
If this resonates with your experience, we would genuinely love to help.
