How to Read a COA
A Certificate of Analysis is the single most important document for any health product. It is the lab receipt that tells you what is actually in the product versus what the label claims. Most people never see one. Here is how to read it when you do.
Step 1: find the lab
The first thing to look for is the laboratory name and its accreditations. A credible COA comes from an ISO 17025 accredited lab, which means their methods and instruments are independently audited. Look for logos or text referencing ISO 17025, NELAP, or state certification numbers.
If the COA does not name the lab, or the lab has no verifiable accreditation, the results are not trustworthy. Some brands produce in-house COAs that are essentially self-graded homework.
Step 2: identify what was tested
The COA should list every analyte tested: individual contaminants or minerals, each on its own row. Common panels include heavy metals (lead, arsenic, cadmium, mercury), PFAS (forever chemicals), microbiological (E. coli, total coliforms), and minerals (calcium, magnesium, silica).
Pay attention to the test method listed for each panel. EPA 200.8 (ICP-MS) for metals is the gold standard. EPA 533 or 537.1 for PFAS. The method determines precision. A COA that does not list methods is hiding something. Learn more in our lab testing methods guide.
Step 3: understand ND vs detected
ND (Not Detected) means the analyte was below the instrument's detection capability. It does not mean zero. It means "below the limit we can measure." This is good news for contaminants but context matters.
Detected means a specific concentration was measured. The value is reported in units like ppb (parts per billion), ppm (parts per million), or mg/L. A detected value is not automatically bad. It depends on the regulatory limit and the substance.
Step 4: MCL vs RL vs MDL
MCL (Maximum Contaminant Level) is the EPA's legal limit. If a detected value exceeds the MCL, it violates federal drinking water standards. See EPA thresholds explained.
RL (Reporting Limit) is the lowest concentration the lab can reliably quantify with a known degree of accuracy. Values below the RL but above the MDL are detected but not precisely quantified.
MDL (Method Detection Limit) is the absolute floor of detection. Below this, the instrument cannot distinguish the analyte from background noise. A lab with a lower MDL gives you more granular data. This matters for substances like lead where there is no safe level.
Step 5: pass, flag, and what they mean
On Alternative Health, we use three statuses. ND means not detected, the best result for contaminants. Pass means the substance was detected but within regulatory limits. Flag means the value exceeds the MCL or a relevant health guideline.
A product can have all "pass" results and still contain detectable contaminants. The question is always: at what level? And compared to what standard? Some health guidelines (like EWG's) are stricter than EPA MCLs.
How to spot incomplete testing
Missing panels: a water COA that only tests minerals but skips heavy metals and PFAS is telling you what is good while hiding what might be bad.
High reporting limits: if the RL for lead is 10 ppb, the lab cannot tell you whether the water contains 9 ppb of lead. A better lab would have an RL below 1 ppb.
No sample chain of custody: a COA should include a sample ID, collection date, and receipt date. Without this, you cannot verify that the tested sample matches the product you are buying.
Old dates: a COA from three years ago may not reflect current production. Reputable brands test each batch or at minimum annually.