Mycotoxin urine test: what it shows and what it doesn't

The result arrives by email. Several lines are marked in red. Since the water damage in the bathroom you have been more tired than you can remember, your head as if wrapped in cotton wool. And now it says: mould toxins in your body. It feels like the proof you have been looking for.

Many people know this moment. If you have had symptoms for a long time that nobody could pin down, you look for something measurable. I do not want to take the result away from you, I want to read it with you. Your symptoms are real. The question is what the test can contribute.

The short answer first. In most people, the mycotoxins a urine test finds come from food. Large European human biomonitoring studies point in this direction, and the German mould guideline assumes the same. A positive result on its own therefore does not prove exposure from your home, and the same guideline sees no indication for this measurement.

What mycotoxins are is explained in the basics of mycotoxins, the big picture in the overview of mould and mycotoxins. This article is about one question: what can a urine profile do, and what can it not do?

What a urine test measures, and why the method determines the number

You read that a urine test shows the mould toxins in your body. That sounds clear-cut: a cup, a laboratory, a number.

What is measured are mycotoxins, that is, metabolic products of moulds, and what your body turns them into. The fungi themselves do not show up in the test. It looks for molecules, not spores.

The profiles differ widely. A German laboratory measures six toxins: aflatoxin, deoxynivalenol, fumonisin, ochratoxin A, T2 toxin and zearalenone. A large US provider lists 29 substances, including gliotoxin, macrocyclic trichothecenes, citrinin and enniatin B. Both are manufacturer information.

Three common names have their own profiles: ochratoxin A, aflatoxin B1 and zearalenone. The toxicology is there, the measurement is here.

Free or bound: the same sample, two answers

The liver attaches glucuronic acid to many mycotoxins, which allows them to pass through the kidneys into the urine. A laboratory can measure only the free toxin, the total after cleavage, or the bound forms directly. According to its sample report, the German laboratory mentioned above measures free mycotoxins.

Sample preparation also shifts the number. A team led by Vidal analysed 96 urine samples with a direct and an indirect method: with enzymatic cleavage, not all glucuronides were converted, so total deoxynivalenol was underestimated.

Antibody test or mass spectrometry

In an immunoassay, often called ELISA, an antibody captures the target molecule, like a key in a lock. But some keys also fit similar locks. This is called cross-reactivity.

A team led by Zhang compared ELISA kits and test strips with mass spectrometry: all tested derivatives of deoxynivalenol and zearalenone showed cross-reactivity, and the sample matrix could amplify the overestimation. Laboratory, cereals That was cereals, not urine, so it illustrates a principle. For urine, the team behind the most cited clinical ELISA study writes itself that components, pH and electrolytes can affect antibody binding.

Liquid chromatography with tandem mass spectrometry, LC-MS/MS for short, separates molecules and determines their mass, with isotope-labelled reference substances as a control. Using this approach, the biomonitoring method of the MAK Commission of the German Research Foundation (DFG) reaches limits of quantification of 0.013 to 0.022 µg/L for aflatoxins and ochratoxin A.

Then there is sensitivity. An early clinical paper gave a detection limit of 2.0 ppb for ochratoxins, that is 2.0 µg/L, roughly two orders of magnitude above the limits of quantification of the validated method. A detection limit and a limit of quantification are not the same thing, but the picture is clear: coarse mesh versus fine mesh. With a coarse net, control subjects often come up empty.

And now you know why two laboratories can tell different stories from the same sample.

Where the mycotoxins in urine come from: mostly from your plate

“But I eat healthily.” I hear this sentence often. And often it is true. Eating healthily just does not reliably protect you from what fungi form in fields and storage facilities.

Deoxynivalenol and zearalenone come mainly from cereals. According to the MAK Commission, the general population takes up ochratoxin A through coffee and cereal products, among other sources. Aflatoxins are found in nuts and spices, for example.

Other data show the same pattern. A team led by Gerding found mycotoxins or their metabolites in 87 percent of samples from 101 people in Germany, with no statistical association with the consumption of staple foods according to a questionnaire. In Sweden, 69 percent of 252 adults had more than one toxin in their urine at the same time. A “multiple finding” is therefore not a special signal.

In a paragraph on sterigmatocystin, the German mould guideline states: mycotoxins are 100 to 1,000 times more concentrated in food than in house dust and bioaerosols, so uptake predominantly through food is to be assumed. According to the same paragraph, a differentiated human biomonitoring study on this is still lacking.

The fair counterpoint: can mould in the room contribute?

In principle, yes. A review of ochratoxin A biomarkers names, alongside food, possible uptake through inhaled air at home and at work. What remains open is how large this share is and whether a urine test can separate it out.

And now you know why a positive urine result does not prove that your home is the source. Food supplies a background that is measurable in the vast majority of people examined.

Which time window a urine value reflects

You hand in the sample on Tuesday morning. What does it measure: Monday evening, the last month or the last year? The answer depends on the toxin.

Half-life in blood is not the same as detection time in urine. According to the MAK Commission, ochratoxin A in urine better reflects acute exposures, serum rather longer-term ones. For gliotoxin, hardly any data on kinetics in humans are available, and the substance is unstable in urine.

Morning urine, 24-hour urine and creatinine

A spot urine sample is a snapshot: drinking a lot means diluted, sweating means concentrated. Adjusting for creatinine compensates for this but has its own blind spots. In 22,245 people from the US survey NHANES III, creatinine depended on age group, sex, body mass index and fat-free mass, among other factors, and the time of day of the sample also made a small, significant difference.

There is no validated rule on what you should eat before the sample, and a large US provider explicitly states no dietary restrictions. The more useful question is how your diet before the sample feeds into the interpretation.

And now you know why a single value is a snapshot with blurred edges.

What studies in people with mould exposure show, and what is criticised about them

Online you come across the sentence: 93 percent of chronically fatigued people had mycotoxins in their urine. That sounds like a clear connection. Let us look at where the number comes from.

An early paper by a team led by Hooper on people with mould exposure found no detectable mycotoxins in control samples, at detection limits of 0.2 ppb for trichothecenes, 1.0 ppb for aflatoxins and 2.0 ppb for ochratoxins. The full text reports a specificity of 100 percent, but a sensitivity for ochratoxin of only 14.3 to 17.4 percent.

The criticism, and what the authors themselves say

In 2016, two commentaries were published. Osterman, an epidemiologist and occupational physician, pointed out that the control group by definition had no mould exposure. His analogy: you would also find more caffeine breakdown products in fatigued people if you compared them with people who never drink coffee. Mendell, an environmental epidemiologist, called the control group unsuitable: appropriate controls would be people without this diagnosis from the same population.

The sharpest counterposition comes from allergology: a review by a team led by Chang considers urinary mycotoxin measurements not validated, while mould can certainly cause allergies and trigger asthma. The German guideline sees sufficient evidence for allergic respiratory diseases, asthma and rhinosinusitis, but insufficient evidence for chronic fatigue syndrome and for neuropsychological and neurotoxic effects. A mould allergy can be tested in line with the guideline, mycotoxin toxicity so far cannot. More on this in the article mould allergy or mycotoxin toxicity.

Clinically, I observe again and again that people come with a traffic light result that unsettles them more than it clarifies. How fatigue and mould might be connected is described in the article on chronic exhaustion and mould, and why the topic is hard to grasp between medical specialties is covered in the article mould and conventional medicine.

And now you know why “93 percent positive” says less than it sounds.

Reference values: why “elevated” is not a clinical cut-off, and how to read a profile

The report shows bars, colours, an arrow pointing up. It looks like a blood count, as if there were a normal range that you have left.

This may be the most important point. There are no validated clinical cut-off values for mycotoxins in urine. According to the German guideline, there are currently no usable and validated test methods for mycotoxins in clinical diagnostics, and according to the CDC, disease-predicting levels have not been established.

Laboratories therefore set their own limits. According to its sample report, a German laboratory gives in-house values for each toxin, adjusted for creatinine. A large US provider describes a traffic light system based on urine samples from 1,000 apparently healthy people: green up to the 75th percentile, yellow up to the 95th, red above that. Both are manufacturer information.

What does that mean? Anyone above the 95th percentile has a higher value than 95 out of 100 people in the comparison group. By definition, then, five percent of the healthy reference group end up in red and another 20 percent in yellow, without being ill. This is not a study figure but the arithmetic logic of percentiles.

Two values sound like cut-offs but are not diagnostic values. The human biomonitoring guidance value of 23 µg/L for deoxynivalenol is a toxicological orientation value for the population. And for ochratoxin A, the European Food Safety Authority considered a health-based guidance value not appropriate in 2020.

Reading a profile without being driven by the traffic light

The following questions are not instructions for interpreting or treating yourself, but material for the conversation with your doctor.

And now you know why no single value is conclusive.

Provocation with glutathione or sauna: why it makes interpretation even harder

Perhaps you were advised to take glutathione or go to the sauna before the sample so that more comes out. The idea sounds logical: what is stored should be possible to draw out.

A US laboratory describes the idea like this: in functional and integrative medicine, glutathione, sauna or other detox-supporting measures are used before urine collection to temporarily increase the excretion of stored mycotoxins. The research could not find a published study validating this for mycotoxin urine tests, nor any human study on mycotoxins in sweat.

What the providers themselves write is remarkable. A large US provider states that its reference ranges were validated on non-provoked samples and that provoked values cannot be derived from them. Another writes that higher numbers after provocation do not indicate the severity of an illness. Then there is physiology: heavy sweating and drinking a lot change dilution and the creatinine adjustment.

You may know this pattern from heavy metals, where broadly validated reference ranges for urine after a chelating agent are also lacking, as described in the article on the DMPS provocation test. I am not evaluating glutathione and sauna themselves here: more on that in the articles on glutathione and mycotoxins and, for cardiovascular problems, on sauna and the heart. If you took glutathione, went to the sauna or sweated heavily before a sample, mention it when the result is discussed.

And now you know why a provocation tends to make the interpretation blurrier rather than sharper.

What makes sense alongside the test, and where measurements in the home also have limits

If urine does not show the source, where do you start? The answer is unspectacular: with your history, your home and your body.

Deutsches Ärzteblatt describes a guideline-based approach. According to self-reports, roughly one in five to one in six homes in Germany is affected by damp or mould. Indoor measurements and blood or urine tests for mould components are generally not indicated in the medical assessment.

First, the exposure history. Water damage, a musty smell, visible mould growth? Do the symptoms improve away from home? Are there occupational exposures? These questions cost nothing and can often say more than a lab value.

Second, the building. Whether there is a source of damp or mould is clarified in the building, not in the urine. According to the mould guide of the German Environment Agency, visible mould growth with an identified cause generally requires no further measurements, and the area should be remediated promptly. Recognised methods include air measurements and material samples according to the DIN ISO 16000 series of standards, while contact plate samples and mould measurements in house dust, for example, are not recommended. Measurements in the home also have limits: the German Environment Agency considers detecting mycotoxins in indoor air or materials unsuitable for routine use because standardised methods and assessment criteria are lacking, and the WHO cannot recommend quantitative health-based threshold values. Practical information can be found in mould in your home, mould found, what now and mould remediation: what is realistic.

Third, the clinical picture. This includes history, physical examination and allergy testing where needed, and if a fungal infection is suspected, separate specialist pathways. For allergic respiratory diseases, asthma and inflammation of the paranasal sinuses, the guideline sees sufficient evidence of an association with damp and mould. More on this in the article on chronic sinusitis.

Fourth, other causes. Fatigue, difficulty concentrating and pain have many possible causes, from the thyroid to iron deficiency to sleep disorders and depression. A broad assessment can protect you from overlooking something important, see chronic fatigue and brain fog and its causes. If you are pregnant, you will find guidance in the article mould during pregnancy.

What the test costs and who pays for it

As an order of magnitude, not as a recommendation: a profile with six toxins cost around 160 euros at a German laboratory in September 2026, billed privately under the German medical fee schedule (GOÄ) according to the laboratory. Because the guideline sees no indication, the test is usually a self-pay service. It can get more expensive afterwards: the CDC case shows how an unsupported interpretation can trigger follow-up costs far above the price of the test.

And now you know why the test comes at the end of the pathway and not at the beginning.

My position: one piece of the puzzle, never proof

In my practice, I take mould seriously as a possible contributing cause of chronic symptoms. Anyone who takes a topic seriously also has to take the limits of their tools seriously.

Can a urine test still make sense? In individual cases, it can be discussed as one piece of the puzzle among many. That requires the building question to have been clarified beforehand, method, form measured and limits to be openly on the table, and nobody deriving a therapy from the result alone. The test is not validated for monitoring the course of a detox, and it never replaces ending the exposure. Detox itself is a separate topic, described in mycotoxin detox: evidence and practice.

Energy is not a luxury, and neither is a home where you can breathe freely. If you would like to have your situation assessed: below this article you will find the option to book an appointment.

And now you know why I neither demonise nor overrate the mycotoxin urine test. It can be one piece of the puzzle, never proof, and it never replaces the question of the source.

Frequently asked questions about the mycotoxin urine test

Where this topic leads