My Top 5 OAT Markers That Changed Everything (And the One Hidden Clue Most People Miss)

Not in a metaphorical “you’re burned out” kind of way. Literally. Biochemically. One single marker on a urine test came back so elevated that my practitioner looked at the results and said, your neuroinflammation is extreme. That marker was quinolinic acid, and it was the beginning of me finally understanding why I felt the way I did foggy, wired-but-tired, anxious, and like my body and brain were operating on completely different frequencies.

The test was the Mosaic Diagnostics Organic Acids Test (OAT) a 76-marker urine analysis that gives you a surprisingly deep look into what’s happening inside your gut, your brain chemistry, your mitochondria, and your nutritional status. All from a single morning urine sample you collect at home.

I’ve run this test multiple times now, and every time it teaches me something new. But there are five markers I come back to again and again five markers that I believe every health-conscious person should understand, whether you’re dealing with chronic fatigue, anxiety, brain fog, gut issues, or just a general sense that something is off and nobody can figure out what.

You can view a sample OAT report here to see exactly what the test looks like and how the markers are organized.

Let’s break down my top five, in plain English, the way I wish someone had explained them to me.

What Is the Organic Acids Test, and Why Does It Matter?

Before we get into the markers, let me give you a quick orientation, because “organic acids” sounds either boring or intimidating depending on your chemistry background.

Organic acids are compounds your body naturally produces as byproducts of metabolism of digesting food, running your mitochondria, processing neurotransmitters, and fighting off pathogens. The key insight is that these acids don’t just disappear. They get filtered through your kidneys and excreted in your urine, which means a urine sample is actually a metabolic snapshot of dozens of things happening in your body simultaneously.

Some of those acids are supposed to be there in certain amounts. Some shouldn’t be there at all. Some should be there but aren’t showing up, which tells its own story.

The Mosaic DX OAT measures 76 of these markers and organizes them into categories: yeast and fungal markers, bacterial markers, mitochondrial function markers, neurotransmitter metabolites, vitamin and mineral status markers, and more. It’s the closest thing to a metabolic report card that I’ve personally come across in the functional medicine world.

And no, your standard blood panel doesn’t catch what this test catches. I’ve had “normal” bloodwork for years while the OAT was flagging serious imbalances. They’re measuring completely different things. A CBC, a CMP, even a thyroid panel all useful in their own context simply do not measure bacterial metabolites in your gut, neurotransmitter breakdown products, mitochondrial efficiency markers, or functional vitamin status. The OAT does all of that, and it does it from one morning urine sample. That’s the efficiency that makes it such a standout tool in functional and integrative medicine.

What I also appreciate is that the OAT looks upstream. It doesn’t just describe symptoms in lab form it gives you mechanistic clues. If your anxiety is driven by a disrupted dopamine pathway caused by a bacterial overgrowth, the OAT will tell you that. If your fatigue is rooted in mitochondrial inefficiency driven by a B vitamin deficiency, it will tell you that too. It asks why, not just what.

If you’re ready to see what’s actually going on inside your body, you can order the Organic Acids Test through My Labs for Life here.

Now, let’s get into the five markers that I think matter most.

Marker #1: Quinolinic Acid: The “Brain on Fire” Marker

This is the one that started it all for me, so let’s give it the attention it deserves.

Quinolinic acid (QA) is a downstream metabolite of tryptophan yes, the same amino acid you associate with turkey and sleep. Under normal circumstances, tryptophan follows a conversion pathway and eventually produces NAD+ (a critical energy molecule) and other beneficial compounds. Quinolinic acid is a middle-step in that pathway, and in a healthy system, the enzyme that converts QA to NAD+ keeps things moving along smoothly.

But here’s where it goes wrong.

When you’re dealing with inflammation, immune activation, or toxic burden particularly phthalate exposure from plastics, personal care products, and food packaging that conversion enzyme gets inhibited. Quinolinic acid backs up in the system like a clogged drain. And elevated QA is not a passive inconvenience. It’s a neurotoxin.

Elevated quinolinic acid acts as an excitotoxin it overstimulates NMDA receptors in the brain, flooding neurons with calcium and triggering a cascade of damage. It promotes oxidative stress (free radical damage inside brain cells), acts as a pro-inflammatory mediator, and research suggests it can compromise the integrity of the blood-brain barrier the protective shield that’s supposed to keep toxins out of your brain tissue.

When my QA came back elevated, my practitioner put it this way: your immune system is activated and it’s turning your own tryptophan into a neurotoxin. The macrophages and microglia the brain’s immune cells were the ones producing it.

What does high quinolinic acid feel like? For me, it was a combination of anxiety that felt almost electrical, difficulty concentrating, mood instability, and a kind of cognitive heaviness that sleep didn’t fix (I was living and working in a moldy environment at the time of this OAT). In research literature, elevated QA has been associated with conditions ranging from depression and anxiety to neuroinflammatory diseases more broadly.

The good news: addressing the underlying drivers, reducing toxic load, calming systemic inflammation, and supporting the kynurenine pathway conversion can bring quinolinic acid down. But you can’t address what you don’t know is there. That’s exactly why this marker matters so much on the OAT.

Marker #2: 4-Cresol: Why I Actually Love This Marker

I know that sounds strange. Why would you love a marker that, when elevated, signals bacterial overgrowth in your gut?

Here’s why: 4-cresol is one of the most actionable markers on the entire OAT. When it’s elevated, you know exactly what you’re dealing with, and the treatment pathway while not always fast or easy is clear.

4-cresol is a metabolite produced by specific strains of Clostridium bacteria most notably Clostridium difficile (yes, the dreaded C. diff) and other problematic Clostridium species. These aren’t the friendly butyrate-producing clostridia. These are the disruptive ones, and the compound they produce, 4-cresol, has a specific and well-documented mechanism of harm.

4-cresol inhibits an enzyme called dopamine beta-hydroxylase, which is responsible for converting dopamine into norepinephrine. When that conversion gets blocked, dopamine accumulates. At first that might sound okay isn’t dopamine the “feel good” chemical? But excess dopamine doesn’t just sit there peacefully. It gets oxidized into toxic quinones that damage neurons, and the downstream deficiency of norepinephrine creates its own set of problems: poor focus, mood dysregulation, fatigue, and a general sense of being emotionally flat.

This also explains something I see clinically discussed a lot: why kids and adults with elevated clostridia markers often display behavioral symptoms aggression, anxiety, self-injurious behavior that seem completely out of proportion to anything else going on in their life. Their dopamine metabolism is biochemically disrupted.

Now, about 15% of OAT tests show elevated 4-cresol as the primary Clostridium marker. It’s less common than its companion marker HPHPA (which we’ll get to next), but no less significant. And what I personally love about it is that it pairs with another marker homovanillic acid (HVA) under the neurotransmitter section  in a pattern that, when you see both elevated together, makes the story undeniably clear. High HVA + elevated 4-cresol = Clostridium is disrupting your dopamine pathway.

That kind of pattern-recognition is part of what makes the OAT so useful. It’s not just isolated numbers it’s a system that tells a story, if you know how to read it.

Marker #3: HPHPA: 4-Cresol’s More Common Cousin

Since we’re already in Clostridium territory, HPHPA deserves its own spotlight because it shows up on more tests and carries some seriously potent neurological effects.

HPHPA – 3-(3-hydroxyphenyl)-3-hydroxypropionic acid is the most common Clostridium marker on the OAT, appearing elevated in roughly 80% of positive Clostridia cases. It’s also produced by pathogenic Clostridium species and, like 4-cresol, it inhibits dopamine beta-hydroxylase. The mechanisms overlap, which is why elevated HPHPA and elevated 4-cresol together create a compounding effect on dopamine metabolism.

But what sets HPHPA apart in the research literature is its documentation in both autism and schizophrenia populations. Dr. William Shaw, who developed the original organic acids test, identified HPHPA as an abnormal phenylalanine metabolite showing up in urine samples from patients with both conditions at rates far above control groups. That research opened a door to understanding gut-brain dysbiosis at a metabolic level that had previously gone largely unexplored.

HPHPA has been described as a potent neurological toxin capable of inducing moodiness, extreme anxiety, aggression, and digestive disruption. Some practitioners describe it as one of the most clinically significant bacterial markers on the entire test.

For people who have never thought about their gut health in neurological terms, HPHPA is often the wake-up call. The gut isn’t just about digestion. When pathogenic bacteria overgrow in the colon and produce compounds like HPHPA, those compounds get absorbed into circulation, cross relevant barriers, and directly interfere with how your brain produces and regulates its own chemistry.

Treatment typically involves targeted antimicrobial interventions either pharmaceutical (like vancomycin, for severe cases) or herbal (berberine, oregano oil, neem, caprylic acid), followed by aggressive probiotic recolonization. But again, you can’t treat what you don’t know is there.

Marker #4: Oxalates: The Sneaky Systemic Disruptor

If quinolinic acid is the dramatic marker that makes people say “oh no,” oxalates are the quiet marker that makes practitioners say “there’s the missing piece.”

Oxalic acid (and its salt form, oxalates) shows up on the OAT in the context of three primary sources: diet (spinach, almonds, beets, dark chocolate, and many “healthy” foods are high-oxalate), fungal/yeast overgrowth (particularly Aspergillus and Candida species), and human metabolism gone sideways.

Here’s what most people don’t know: certain fungi in your gut produce oxalates as a byproduct. When you have significant Candida overgrowth, your OAT will often show elevated yeast markers and elevated oxalates together a double pattern that explains why some people on anti-Candida protocols feel significantly worse when they die off. The oxalate load temporarily spikes before it clears.

Why do oxalates matter systemically? A few reasons.

First, oxalates bind calcium and can deposit in tissues including the kidneys (kidney stones are primarily calcium oxalate), joints, muscles, and even connective tissue. People with chronic muscle pain, unexplained joint aches, or vulvodynia frequently have elevated oxalates on their OAT.

Second, high oxalates can impair mitochondrial function by interfering with several energy-production enzymes. This creates a fatigue that no amount of coffee or sleep seems to fix.

Third, elevated oxalates pull minerals out of circulation, particularly calcium and magnesium, which creates downstream deficiencies that affect everything from muscle function to nerve transmission to mood.

The frustrating thing about oxalate issues is that they often develop gradually, and the dietary culprits are frequently foods that health-conscious people eat more of smoothies with spinach and almonds, nut-heavy paleo or keto diets, dark chocolate. The OAT is often the first test that reveals this is a problem, because standard bloodwork doesn’t measure it.

The OAT lets you see whether oxalates are coming primarily from diet, from fungal overgrowth, or from a metabolic issue and that distinction completely changes how you address it.

Marker #5 (My Pick): Pyruvic Acid + Lactic Acid: The Hidden B1 Signal Nobody Talks About

This is the one I promised you. The one that most people even practitioners who’ve been reading OATs for years don’t always catch in its full significance.

On the OAT, there’s a section covering mitochondrial metabolic function that includes pyruvic acid and lactic acid. When both of these markers are elevated simultaneously, it creates a pattern that points directly to impaired function of the pyruvate dehydrogenase complex (PDH) the enzymatic gateway that converts pyruvate into acetyl-CoA so it can enter the Krebs cycle and actually produce cellular energy.

And what does the PDH complex require to function? Thiamine. Vitamin B1.

This is the hidden signal. Elevated pyruvate + elevated lactate on the OAT is one of the earliest and most actionable functional indicators of thiamine (B1) deficiency and it shows up before you’d ever see it on a standard serum thiamine test. Functional B1 deficiency means your cells don’t have enough thiamine to run their metabolic machinery properly, even if your blood levels look “normal.”

Why does this matter so much? Because B1 deficiency is wildly underdiagnosed in the modern population, and its symptoms are devastatingly broad: fatigue that no amount of rest resolves, peripheral neuropathy (tingling or numbness in hands and feet), brain fog, poor memory, anxiety, heart palpitations, and in severe cases, the neurological syndrome called Wernicke’s encephalopathy.

The people most at risk are those who eat a high-carbohydrate diet (carbohydrate metabolism burns through thiamine at an accelerated rate), people who consume alcohol regularly (alcohol depletes B1 aggressively), people who drink large amounts of coffee or tea (tannins and caffeine impair B1 absorption), and anyone under chronic physical or metabolic stress.

Here’s what makes it even trickier: when you eat a high-carb meal and then feel unusually fatigued, foggy, or heart-poundy afterward, that can be a functional B1 sign. Your body burned through its thiamine reserves to process the carbohydrates, and now there’s not enough left for clean mitochondrial function.

The OAT reveals this pattern functionally through the pyruvate-to-lactate ratio and the elevated levels of both in a way that most standard panels completely miss. An elevated 3-methyl-2-oxovaleric acid (marker #75 on the OAT) alongside this pattern adds even more weight to the B1 deficiency signal.

This is exactly the kind of clinical gem that makes the OAT worth running, especially if you’ve been chasing answers on more conventional testing and coming up empty. Most practitioners won’t think to check functional B1 status. But the OAT pattern is right there, waiting to be read.

Why I Keep Coming Back to This Test

I’ve done a lot of lab testing in my health journey. Stool tests, hormone panels, food sensitivity tests, heavy metal testing, genetic testing. Some of them have been useful. Some have been expensive noise.

The OAT is consistently in the “actually useful” category for me not because it gives me everything, but because it gives me metabolic context that I can’t get anywhere else. It tells me what my gut bacteria are doing to my brain chemistry. It tells me whether my mitochondria are running clean. It gives me a functional read on B vitamins that standard blood panels can’t capture. And it shows me neuroinflammation markers that explain symptoms I’ve been dismissing as stress or aging or just “that’s how I feel now.”

The sample OAT report from Mosaic Diagnostics is worth looking at so you can get a sense of how the 76 markers are organized and what the data actually looks like in practice. It’s more readable than you’d expect.

For me, the five markers above quinolinic acid, 4-cresol, HPHPA, oxalates, and the B1/pyruvate-lactate pattern have collectively told me more about the root causes of my symptoms than years of conventional workups. They’ve guided specific, targeted interventions: antimicrobial protocols, oxalate-lowering strategies, thiamine supplementation, toxin reduction, and neuroinflammation support. And over time, re-running the test has let me see whether those interventions are actually moving the markers not just how I feel, but biochemically.

That’s the thing about functional testing done well. It gives you a feedback loop. You’re not just guessing.

Who Should Consider Running the OAT?

Honestly? Almost anyone who is health-motivated and hasn’t had their organic acids tested. But more specifically, the OAT tends to be highest-yield for people dealing with:

• Chronic fatigue that doesn’t respond to sleep or rest
• Brain fog, poor memory, or difficulty concentrating with no clear cause
• Anxiety, depression, or mood instability that hasn’t fully responded to standard interventions
• Digestive issues including bloating, irregular bowel habits, or food sensitivities
• Unexplained muscle pain, joint aches, or chronic inflammation
• Autoimmune conditions where gut health and systemic inflammation are likely contributing factors
• Children or adults on the autism spectrum, where gut-brain dysbiosis and dopamine disruption are common and often undertreated
• Anyone who suspects their gut health may be affecting their mental health which, given the research, is probably far more people than realize it

If you’ve been told “everything looks normal” on standard lab work but you know something is off, the OAT is often the test that finally provides answers. It’s not a replacement for a comprehensive clinical evaluation, but it adds a layer of metabolic specificity that conventional testing simply doesn’t offer.

You deserve data that matches the complexity of what you’re experiencing. Order the Organic Acids Test here and start reading the signals your body has been sending all along.

The Mosaic Diagnostics OAT is a simple at-home urine collection. You order the test, receive a kit, collect a first-morning urine sample (you’ve been fasting overnight, so the organic acid concentration is highest), and ship it back to the lab. Results typically take a couple of weeks.

The report is comprehensive 76 markers across multiple categories so I highly recommend working with a practitioner who knows how to read the patterns, not just the individual elevated markers. The markers are most useful in context with each other, as I’ve tried to show throughout this post.

That said, even running the test and reading the education materials is eye-opening. The sample report helps. And there are practitioners who specialize in OAT interpretation who can walk you through your results.

If you’re ready to stop guessing and start getting real data on what’s happening inside your body, order the Organic Acids Test through My Labs for Life here. It’s one of the highest-yield functional tests I’ve come across, and for anyone dealing with chronic symptoms brain fog, fatigue, mood issues, gut problems, unexplained aches it’s often the missing piece.

Your body is leaving clues everywhere. The OAT helps you read them.

These statements are for educational purposes and are not intended to diagnose, treat, cure, or prevent any disease. Always work with a qualified healthcare practitioner to interpret lab results and guide any treatment decisions.

References

1. Guillemin GJ. “Quinolinic acid, the inescapable neurotoxin.” The FEBS Journal. 2012;279(8):1356–1365. doi:10.1111/j.1742-4658.2012.08485.x  Landmark review establishing quinolinic acid as a brain endogenous excitotoxin produced by macrophages and activated microglia during neuroinflammation, acting via NMDA receptor agonism and disruption of the blood-brain barrier.
2. Mosaic Diagnostics. “How the Organic Acids Test Provides Insights into Toxic Exposures.” MosaicDX.com, 2024. https://mosaicdx.com/resource/how-the-organic-acids-test-provides-insights-into-toxic-exposures/ Describes the mechanism by which environmental phthalates inhibit the enzyme converting quinolinic acid to nicotinamide, causing QA accumulation and downstream neuroinflammation.
3. Shaw W. “Increased urinary excretion of a 3-(3-hydroxyphenyl)-3-hydroxypropionic acid (HPHPA), an abnormal phenylalanine metabolite of Clostridia spp. in the gastrointestinal tract, in urine samples from patients with autism and schizophrenia.” Nutritional Neuroscience. 2010;13(3):135–143. doi:10.1179/147683010X12611460763968 — Foundational paper identifying HPHPA and 4-cresol as Clostridium metabolites significantly elevated in urine samples from patients with autism and schizophrenia.
4. Shaw W. “Inhibition of Beta-oxidation Pathway of Fatty Acids and Dopamine-Beta-Hydroxylase by Phenyl Derivatives of Short-Chain Fatty Acids from Gastrointestinal Clostridia Bacteria is a Major Cause of Autism.” Published via Mosaic Diagnostics / PubMed. PMID: 37363147. Details the mechanism by which HPHPA and 4-cresol inhibit dopamine beta-hydroxylase, leading to dopamine accumulation, norepinephrine deficiency, and toxic dopamine quinone production in the brain.
5. Passmore IJ, Letertre MPM, Preston MD, et al. “Clostridioides difficile infection increases circulating p-cresol levels and dysregulates brain dopamine metabolism: linking gut-brain axis to autism and other neurologic disorders.” bioRxiv (preprint). 2021. doi:10.1101/2021.10.22.465382 Demonstrates that C. difficile infection drives elevated circulating p-cresol (4-cresol), inhibits dopamine beta-hydroxylase, and disrupts dopaminergic signaling in brain regions relevant to neurodevelopmental disorders.
6. Pascucci T, Colamartino M, Fiori E, Sacco R, Coviello A, Ventura R, et al. “P-cresol Alters Brain Dopamine Metabolism and Exacerbates Autism-Like Behaviors in the BTBR Mouse.” Brain Sciences. 2020;10(4):233. doi:10.3390/brainsci10040233. Animal model study confirming that 4-cresol exposure directly alters brain dopamine metabolism and amplifies autism-like behavioral phenotypes.
7. Mosaic Diagnostics. “Guide to Oxalate Test Results.” MosaicDX.com, 2024. https://mosaicdx.com/resource/oxalates-great-plains-laboratory/ Clinical overview explaining how Candida and Aspergillus species produce oxalates via glyoxalate pathway intermediates, and how proportional vs. disproportional oxalate elevations on the OAT guide clinical interpretation.
8. Mosaic Diagnostics. “Oxalate Control.” MosaicDX Clinical Reference Document. https://mosaicdx.com/wp-content/uploads/2023/02/GPL_Oxalate-Control.pdf  Reviews the three primary sources of urinary oxalates (diet, fungal overgrowth, and human metabolism), the correlation between elevated arabinose and high oxalates, and management strategies including calcium-magnesium citrate supplementation.
9. HealthMatters.io. “Oxalic Acid — Organic Acids Test (OAT) Biomarker Explanation.” https://healthmatters.io/understand-blood-test-results/oxalic Summarizes the clinical significance of elevated urinary oxalates on the OAT, including associations with kidney stones, fibromyalgia, vulvodynia, autism, muscle pain, and cardiac abnormalities.
10. MedLink Neurology. “Thiamine (B1) Deficiency.” Updated 2025. https://www.medlink.com/articles/thiamine-deficiency  Comprehensive neurological reference establishing that impaired pyruvate dehydrogenase activity from thiamine deficiency leads to elevated pyruvate and lactate, noting that subclinical thiamine deficiency presents with vague symptoms including fatigue, irritability, headache, and lethargy long before overt neurological signs appear.
11. Donnino M. “Effect of Thiamine on Pyruvate Dehydrogenase Activity in Septic Shock.” NIH Grant K02-HL107447-01A1. — NIH-funded research establishing thiamine as an essential cofactor for the pyruvate dehydrogenase complex, confirming that thiamine deficiency causes anaerobic metabolism predominance and lactic acidosis, and that thiamine administration can rapidly reverse this biochemical pattern.
12. Mosaic Diagnostics. “Organic Acids Test (OAT) 101: Essential Information for the Practitioner New to the OAT.” MosaicDX.com, 2025. https://mosaicdx.com/resource/organic-acids-test-oat-101-essential-information-for-the-practitioner-new-to-the-oat/ Practitioner-facing primer covering OAT marker categories, pattern recognition for Clostridium (4-cresol, HPHPA, HVA correlation), the kynurenine pathway and quinolinic acid as a neuroinflammation marker, and clinical treatment considerations for bacterial overgrowth.