What Is the Organic Acids Test?

The Organic Acids Test (OAT) is a urine-based metabolic test that measures over 70 organic acid metabolites produced by human cells, gut bacteria, and yeast. Unlike stool-based microbiome tests that directly measure which organisms are present, the OAT takes an indirect approach — it measures the metabolic byproducts these organisms produce, which are absorbed into the bloodstream and excreted in urine. Think of it as detecting smoke rather than looking for the fire itself.

The OAT is primarily offered by Mosaic Diagnostics (formerly Great Plains Laboratory) and is widely used by functional medicine practitioners, integrative nutritionists, and naturopathic doctors. It is not a standard test in conventional gastroenterology, which means you are unlikely to have your regular doctor order it or your insurance cover it.

How the OAT Relates to Gut Health

The gut-related markers on the OAT fall into several key categories:

Yeast and Fungal Markers

Elevated levels of arabinose, tartaric acid, and several other organic acids are associated with Candida and other fungal overgrowth in the gut. These markers are among the most clinically useful on the OAT because yeast overgrowth is difficult to detect on standard stool tests. Yeast organisms tend to adhere to the intestinal mucosa rather than shedding consistently into stool, so urine metabolites can be more reliable indicators of overgrowth.

Bacterial Dysbiosis Markers

Several organic acids serve as indicators of specific types of bacterial overgrowth:

  • HPHPA (4-hydroxyphenylacetic acid) — elevated levels are associated with Clostridium species overgrowth, which can produce neurotoxic metabolites
  • 4-cresol — another marker of Clostridium species that has been linked to altered dopamine metabolism
  • D-arabinitol — a specific marker of Candida overgrowth that is more specific than arabinose alone
  • Hippuric acid — can indicate bacterial overgrowth or high dietary benzoate exposure
  • Dihydroxyphenylpropionic acid (DHPPA) — reflects beneficial Lactobacillus and Bifidobacterium activity. Low levels may suggest insufficient beneficial flora
The OAT does not diagnose gut infections or specific conditions. It provides metabolic clues that, when interpreted in the context of symptoms and clinical history, can guide further investigation and treatment decisions. It is a compass, not a map.

Mitochondrial and Energy Markers

While not directly gut markers, the mitochondrial function indicators on the OAT are relevant because mitochondrial dysfunction can impair intestinal epithelial cell energy production, weakening the gut barrier. Markers like succinic acid, fumaric acid, and malic acid reflect Krebs cycle efficiency and can indicate whether your cells — including gut lining cells — are producing energy effectively.

Nutrient Markers

The OAT includes markers for B vitamin status, vitamin C sufficiency, CoQ10, and N-acetylcysteine (glutathione precursor). These nutrients are essential for gut barrier maintenance, immune function, and detoxification. Deficiencies in B vitamins, for example, can impair intestinal cell turnover and mucosal repair.

Strengths of the OAT

  • Non-invasive collection — a first-morning urine sample is significantly easier to collect than stool
  • Functional perspective — measures what organisms are doing (their metabolic output) rather than just whether they are present
  • Yeast detection — arguably the best non-invasive test for detecting fungal overgrowth in the gastrointestinal tract
  • Broad metabolic overview — provides information about nutrient status, detoxification capacity, neurotransmitter metabolism, and mitochondrial function alongside gut markers
  • Well-suited for children — urine collection is far easier than stool collection in paediatric populations

Limitations and Criticisms

  • Limited peer-reviewed validation — while individual organic acid markers have research support, the comprehensive OAT panel has not been rigorously validated in large clinical trials
  • Interpretation complexity — results require expertise to interpret correctly. Without a knowledgeable practitioner, the report can be confusing or misleading
  • Dietary influence — some markers are significantly influenced by recent food intake, medications, and supplements, potentially producing false positives
  • Cost — typically 300 to 400 dollars out of pocket, as it is not covered by most insurance plans
  • Not a standalone diagnostic — should always be combined with clinical history, symptoms, and potentially other testing

Getting the Most From an OAT

If you decide to take an OAT, work with a practitioner who has experience interpreting the results. Collect the sample following the instructions precisely, particularly the fasting requirement and the need to avoid certain supplements for 48 hours prior. Document your symptoms and diet in the days leading up to the test so that abnormal markers can be correlated with your actual experience. GutIQ's symptom tracking data can be invaluable here, providing your practitioner with detailed context that makes OAT interpretation more meaningful and clinically relevant.