Matcha testing transparency guide
Most matcha brands say they test. Few publish the actual numbers. This guide explains what good testing looks like, what markers matter, and how to evaluate whether a brand's testing claims are credible.
Why this matters: Matcha is a whole-leaf powder. You consume everything in the leaf, including any heavy metals or pesticide residues present in the soil or applied during cultivation. The only way to verify safety is third-party lab data with specific values from a named, accredited laboratory.
About this page
SteadyMatcha is a research and discovery platform. We do not currently sell our own matcha product. This page is an educational guide about testing transparency, not a page about our own product testing. We track which brands publish lab data and make that information easy to compare. See the brand directory.
What matcha should be tested for
These are the three categories of contaminants that matter for matcha safety. They align with what food safety regulators in the US, EU, and Japan require.
Heavy metals
Matcha is grown in soil, and soil can contain naturally occurring heavy metals — particularly lead and cadmium. Because matcha is a whole-leaf powder (not a brewed extract), these metals concentrate in the final product. The four metals regulated under major food safety frameworks are:
Lead (Pb)
California Prop 65 limit: 0.5 µg/day
Cadmium (Cd)
EU food safety limit: 0.2 mg/kg
Arsenic (As)
FDA action level: 10 ppb (inorganic)
Mercury (Hg)
FDA action level: 1 ppm
Pesticide residues
A comprehensive pesticide panel covers 200+ individual compounds, including organophosphates, pyrethroids, neonicotinoids, fungicides, and herbicides. EU MRL (Maximum Residue Level) standards are among the strictest in the world for tea products.
Note: organic certification and actual pesticide testing are different things. A brand can be certified organic and still have pesticide residues from neighboring farms or soil contamination. Published pesticide panel results are more informative than certification claims alone.
Microbiology
Microbial testing covers total aerobic plate count, yeast and mold, coliforms, E. coli, and Salmonella. Stone-ground matcha is a minimally processed product — microbial testing confirms the powder was handled under appropriate conditions from harvest through packaging.
What ISO 17025 accreditation means
ISO 17025 is the international standard for testing and calibration laboratories. A lab that holds ISO 17025 accreditation has been independently audited to verify that its testing methods are technically sound, its equipment is properly calibrated, and its results are reproducible and traceable to international measurement standards.
This matters because not all labs are equal. A brand can claim "third-party tested" using a lab with no formal accreditation, no audited methods, and no way to verify the results. ISO 17025 accreditation is the minimum standard that regulators, food companies, and importers use to determine whether a lab result is credible.
When evaluating a brand's testing claims, look for the specific lab name and verify independently that it holds ISO 17025 accreditation for the relevant test methods. Common accredited food testing labs include Eurofins Scientific, NSF International, and Intertek.
How to read a Certificate of Analysis
A Certificate of Analysis (COA) is a document issued by a testing laboratory that reports the results of analytical testing on a specific sample. When evaluating a matcha COA, look for these elements:
Named laboratory
The COA should identify the testing lab by name. Look up the lab independently to verify it holds ISO 17025 accreditation for the relevant test methods.
Specific numeric values
A credible COA shows the actual measured value (e.g., 0.04 µg/g lead), not just 'pass' or 'not detected' without a number. 'Not detected' should include the method detection limit (MDL) so you know how sensitive the test was.
Sample identification
The COA should reference a specific batch, lot number, or sample ID that can be traced back to the product you purchased. A COA without a batch reference may not apply to your specific product.
Test date
COAs should be recent. A COA from three years ago does not tell you anything about the batch you are buying today. Each batch should have its own dated COA.
Applicable limits
The COA should show the regulatory or internal limit for each analyte alongside the measured value, so you can assess whether the result is within an acceptable range.
What we track across brands
SteadyMatcha tracks testing transparency across the most popular matcha brands sold in the US. For each brand, we note:
Whether heavy metals COA data is published (not just claimed)
Whether the lab name is disclosed
Whether the lab holds ISO 17025 accreditation
Whether specific numeric values are shown (not just pass/fail)
Whether results are batch-specific or generic
Whether pesticide panel results are published
Whether microbial results are published
Why publishing the numbers matters
The matcha industry has a transparency problem. Most brands claim to test but publish nothing. Some publish a single COA from years ago and apply it to all products. A few publish COAs on request — but only if you ask.
Publishing specific numeric values publicly — not just a "tested" badge — is the only way for consumers to verify what they are putting in their bodies. The numbers are either good or they are not. Hiding them helps no one except brands with something to hide.
We believe every matcha brand should publish full numeric COA data for every batch. We track which brands do this and make that information easy to find and compare.