Medically Reviewed by Dr. Steven Campbell, MD
How to read a Certificate of Analysis
A real Marek Supplements batch — Liver Support, Lot 26011349 — decoded section by section.
Learn what every number, lab method, and limit means, and how to tell a thorough report from a marketing claim.
Read any COA in 60 seconds
- Locate the LOT number. The 8-digit code on the bottom of your bottle ties to a single batch and a single report.
- Confirm the pass count. A complete COA tests every active ingredient, four heavy metals, six microbiological screens, and at least one allergen.
- Verify potency. Each measured ingredient should land between 90–120% of its label claim.
- Read contamination as % of regulatory limit. Heavy metals and gluten should sit at a small fraction of their allowable ceiling — not just under it.
- Check the lab credentials. ISO/IEC 17025 accreditation, a named laboratory director, and a recent test date.
A Certificate of Analysis (COA) is a lab-issued document confirming what's actually in a supplement batch. It lists what was tested, the methods used, the limits applied, and the measured results. In an industry where third-party audits routinely find products under-dosed by 30% or more, a published, batch-specific COA is the only way to verify that the bottle in your hand contains what the label claims — and nothing it shouldn't.
The trouble is that COAs aren't written for consumers. They're written for chemists, regulators, and auditors. This guide translates one — start to finish — using a real, recently released batch of Marek Liver Support as the worked example.
1 The header
Product, LOT, and the pass count
Every COA opens with the product, batch identifier, and a top-line indicator of how many tests were run and how many passed. This is the first thing to scan — and the first place a thin report gives itself away.
From the Liver Support COA
Liver Support
Lot 26011349
15 / 15 Tests Passed
Supports Healthy Liver Function · 180 Capsules · 2 Capsules Per Serving
Non-GMO
Gluten Free
Dairy Free
Soy Free
Vegetarian
What "15 / 15" actually counts
Four active ingredients verified for potency, four heavy metals screened, six microbiological screens, and one allergen test — that's the 15. A complete COA tests every active separately, not just one "representative" sample. If a report shows fewer tests than ingredients, that's a thin report.
Watch for vague "tested" language
"Third-party tested" with no batch number, no lab name, and no method list is a marketing line — not verification. A real COA names the batch, the lab, the analyte, and the result.
2 The label claim
What the bottle says is inside
The Supplement Facts panel restates what's printed on the label — the ingredients and doses the brand is committing to. The rest of the COA exists to verify whether that commitment was met.
Supplement Facts · Per 2 Capsules
What's Inside
Per 2 Capsules · 90 servings per bottle
TUDCA Tauroursodeoxycholic Acid
500 mg
CDP Choline Citicoline
300 mg
Glycine
225 mg
Myo-Inositol
150 mg
Read this as a contract
These four numbers — 500, 300, 225, 150 milligrams — are the doses the brand has promised. In the next section, the lab will measure each one independently. The closer the measured value sits to the labeled value, the better the formulation control.
3 Third-party labs
Two third-party labs — and why one isn't enough
"Third-party tested" only means something when the labs are named, ISO/IEC 17025–accredited for the specific tests they're running, and split across safety and potency so no single facility grades its own work.
Laboratory partners
Safety Testing
Summit Nutritional Laboratories
Potency & Allergens
Harken Research Laboratories
ISO/IEC 17025 is the gold standard
Why two specialist labs, not one full-service lab
Heavy metals and microbes need instruments and method scopes that differ from those used for active-ingredient quantification. A single facility might be accredited for one but not the other. Splitting the work — Summit for safety, Harken for potency and allergens — means each test runs at a lab whose accreditation specifically covers it.
4 Potency verification
Was every milligram actually in the capsule?
This is the most consequential section of any supplement COA. The lab measures each active ingredient directly and compares it to the label claim. Here's TUDCA from the Liver Support batch — read it carefully.
Ingredient Verification
4 actives · HPLC & LC-MS/MS
TUDCA
Tauroursodeoxycholic Acid · HPLC
Measured
524.78 mg
Label claim
500 mg
500 mg
80%90%100%110%120%130%
105.0% of label
90–120% target zone
Why is the measured amount higher than the label?
This surprises most readers. The overage is intentional. Active ingredients degrade slowly across a product's shelf life — sometimes by 10–15% over two years. Formulating at 105% of label at the time of release means the capsule will still deliver close to 100% near expiration. A measurement of 70% would mean under-dosed; a measurement of 150% would suggest a formulation problem. The 90–120% target zone exists for this reason.
HPLC and LC-MS/MS — what's actually happening
HPLC (High-Performance Liquid Chromatography) pushes the sample through a column under high pressure to separate the compounds inside it. LC-MS/MS adds two stages of mass spectrometry, which lets the lab identify and quantify a specific molecule even in a complex botanical or mineral matrix. Together they answer two questions: is the right molecule present, and how much of it.
All four actives from this batch
TUDCA
Bile acid
Measured
524.78 mg
Label
500 mg
500 mg
105.0% of label
CDP Choline
Citicoline
Measured
303.83 mg
Label
300 mg
300 mg
101.3% of label
Glycine
Amino acid
Measured
260.63 mg
Label
225 mg
225 mg
115.8% of label
Myo-Inositol
Cell signaling cofactor
Measured
151.19 mg
Label
150 mg
150 mg
100.8% of label
All four actives sit inside the 90–120% zone
The tightest reading (Myo-Inositol at 100.8%) and the widest (Glycine at 115.8%) both fall comfortably inside the target band. This is what tight formulation control looks like — not perfect 100% readings, which would actually be slightly suspicious given measurement variability.
5 Heavy metals
Reading contamination as % of allowable limit
Heavy metals — arsenic, cadmium, lead, mercury — can concentrate in raw materials. The pharmaceutical-grade standard for testing them in supplements is USP <2232>, which sets a daily exposure ceiling for each. The question isn't just "did it pass?" — it's "how close to the limit?"
Heavy Metals
4 analytes · USP <2232> · ICP-MS
Arsenic
USP <2232> · ICP-MS
Result
0.147 mcg
Limit
< 15 mcg
< 15 mcg
0.98% of allowable limit
Cadmium
USP <2232> · ICP-MS
Result
< 0.001 mcg
Limit
< 5 mcg
< 5 mcg
< 0.02% of allowable limit
Lead
USP <2232> · ICP-MS
Result
0.031 mcg
Limit
< 5 mcg
< 5 mcg
0.62% of allowable limit
Mercury
USP <2232> · ICP-MS
Result
< 0.001 mcg
Limit
< 15 mcg
< 15 mcg
< 0.007% of allowable limit
"Pass" tells you almost nothing on its own
USP <2232> lets a daily supplement deliver up to 15 mcg of arsenic, 5 mcg of cadmium, 5 mcg of lead, and 15 mcg of mercury. A batch at 99% of the limit "passes." So does this one at < 1%. The percentage framing makes the gap visible: this batch's lead reading sits at 0.62% of the allowable ceiling — meaningfully cleaner than the regulatory floor.
ICP-MS — the reference method for trace metals
Inductively Coupled Plasma Mass Spectrometry ionizes the sample in plasma hotter than the surface of the sun, then sorts the resulting ions by mass. It can detect heavy metals at parts-per-billion sensitivity, which is what makes the "< 0.001 mcg" results possible — the lab is measuring below the detection threshold for cadmium and mercury entirely.
6 Microbiology
Six screens for what shouldn't be in your supplement
Microbiology testing confirms the finished product isn't contaminated with bacterial or fungal organisms. Six standard screens cover the categories that matter: total counts, coliforms, three pathogens, and yeasts and molds.
Microbiology
6 screens · AOAC & PCR
| Test | Method | Specification | Result | Status |
|---|---|---|---|---|
| Total Plate Count | AOAC 2015.13 | < 1,000 cfu/g | < 100 cfu/g | Pass |
| Total Coliform | AOAC 2018.13 | < 100 cfu/g | < 100 cfu/g | Pass |
| E. coli | PCR | None Detected | None Detected | Pass |
| Salmonella spp. | PCR | None Detected | None Detected | Pass |
| S. aureus | PCR | None Detected | None Detected | Pass |
| Yeasts & Molds | AOAC 2014.05 | < 1,000 cfu/g | < 100 cfu/g | Pass |
cfu/g — Colony Forming Units per gram
A microbiological count of viable organisms able to reproduce. "< 100 cfu/g" means fewer than 100 colonies grew per gram of sample under controlled lab conditions. The specifications shown are pharmaceutical-grade limits; the results sit an order of magnitude below.
Why two methods — AOAC and PCR
AOAC methods culture the organisms on growth media and count colonies. They're the right tool for total counts and yeasts/molds. PCR (Polymerase Chain Reaction) detects organism-specific DNA sequences directly — far more sensitive for confirming the absence of dangerous pathogens like E. coli, Salmonella, and Staphylococcus aureus.
7 Allergen testing
Gluten Testing — even in a supplement with no grains
A "Gluten Free" badge on the bottle is only meaningful if the finished product has been measured. Cross-contamination during manufacturing can introduce trace gluten from shared equipment, raw material sourcing, or encapsulation aids. This batch is tested by sandwich ELISA against the FDA's 21 CFR 101.91 threshold.
Allergen Testing
1 allergen · Sandwich ELISA
Gluten
Sandwich ELISA · ESS 6.2.6
Result
< 5 ppm
FDA Gluten-Free Limit
< 20 ppm
< 20 ppm
Below detection — the assay's 5 ppm sensitivity floor sits well under the FDA's 20 ppm threshold (21 CFR 101.91)
Allergen testing by Harken Research Laboratories, with ELISA analysis subcontracted to Exact Scientific Services (Ferndale, WA · ISO/IEC 17025 · ANAB AT-1754). Tested April 1–2, 2026.
Why test a non-grain supplement for gluten?
None of the four actives in Liver Support are grain-derived. So why test? Because cross-contamination is real — shared facility lines, raw materials processed near grain-adjacent ingredients, or encapsulation aids can all introduce trace gluten. A "Gluten Free" label without finished-product testing is an assumption. ELISA on the finished capsule is the proof.
Sandwich ELISA — how the test works
ELISA (Enzyme-Linked Immunosorbent Assay) uses antibodies that bind specifically to gluten proteins. In the "sandwich" configuration, gluten is captured between two antibodies — the first binds it to a plate, the second carries an enzyme that produces a color signal proportional to the amount present. The ESS 6.2.6 method has a detection limit around 5 ppm. A result of "< 5 ppm" means gluten was undetectable even at that sensitivity — well below the FDA's 20 ppm gluten-free threshold under 21 CFR 101.91.
What this means for celiac and gluten-sensitive customers
A < 5 ppm reading is the strongest available verification short of dedicated gluten-free facility certification. The FDA's threshold of 20 ppm is the level below which the agency considers a product safe for individuals with celiac disease. This batch measures at less than a quarter of that ceiling — within the assay's detection floor.
8 Lab signatures
Who signed off — and when
A real COA closes with named laboratory directors, dated signatures, and full accreditation details. Anonymous reports, missing dates, or generic "lab" attribution are signs that something hasn't been done the right way.
Authorized signatures from this batch
Safety Testing
Summit Nutritional Laboratories
2600 North Main Street
Spanish Fork, Utah 84660
Spanish Fork, Utah 84660
Joel L. Nelson
Laboratory Director
Signed February 24, 2026
Potency & Allergens
Harken Research Laboratories
11 W. Del Mar Blvd, Suite 240
Pasadena, CA 91105
Pasadena, CA 91105
Josh Snyder
Laboratory Director
Signed April 7, 2026
Named, dated, accredited — the three signals that matter
The signatures attach individual accountability to the results. The dates confirm testing recency — both signatures here are within months of the batch's release. If a COA you're reading is signed years before the bottle's manufacture date, that's a single sample from an old lot, not verification of what's in your hand.
Reference
Glossary of COA terms
Every lab method, accreditation, and unit that appears on a Marek Supplements Certificate of Analysis — defined plainly.
ICP-MS Inductively Coupled Plasma Mass Spectrometry
The reference method for measuring trace metals. Ionizes the sample in argon plasma, then sorts the ions by mass to detect arsenic, cadmium, lead, mercury, and minerals at parts-per-billion sensitivity.
HPLC High-Performance Liquid Chromatography
Separates the compounds in a liquid sample by pushing it through a column under high pressure. Each compound travels at a different rate, allowing it to be measured individually.
LC-MS/MS Liquid Chromatography–tandem Mass Spectrometry
Combines HPLC separation with two stages of mass spectrometry. The most specific method available for identifying and quantifying a target molecule in a complex sample.
ELISA Enzyme-Linked Immunosorbent Assay
An antibody-based test that detects a specific protein. In supplement testing, sandwich ELISA is the standard method for measuring gluten — binding it between two antibodies and producing a quantifiable color signal.
USP <2232> U.S. Pharmacopeia General Chapter
The standard that sets permitted daily exposure limits for elemental contaminants — arsenic, cadmium, lead, mercury — in dietary supplements. Aligned with pharmaceutical-grade limits.
21 CFR 101.91 FDA gluten-free regulation
The FDA's labeling rule defining "gluten-free" for food and supplements. A product must contain less than 20 parts per million (ppm) of gluten to qualify for the claim.
AOAC AOAC International methods
A library of officially validated analytical methods used worldwide. AOAC methods are the default reference for food and supplement microbiology testing.
PCR Polymerase Chain Reaction
A DNA-based method for detecting specific microorganisms — E. coli, Salmonella, S. aureus — at extremely low concentrations by amplifying and identifying their genetic signature.
ISO/IEC 17025 Laboratory competence standard
The international standard for testing and calibration laboratories. Accreditation confirms a lab's methods, equipment, personnel, and quality systems meet globally recognized criteria.
ppm Parts per million
A unit of concentration: 1 ppm equals 1 milligram per kilogram. Used to express trace levels of allergens and contaminants where percentages would be unwieldy.
cfu/g Colony-Forming Units per gram
A microbiology count: the number of viable bacterial or fungal cells able to reproduce under lab conditions, normalized per gram of sample. The standard unit for microbial contamination limits.
PJLA Perry Johnson Laboratory Accreditation
A U.S.-based ISO/IEC 17025 accreditation body. PJLA audits and certifies laboratories' technical competence and quality systems.
ANAB ANSI National Accreditation Board
A major U.S. accreditation body for ISO/IEC 17025 testing labs. Operated by the American National Standards Institute.
mcg Microgram (one-millionth of a gram)
One thousand micrograms equals one milligram (mg). Heavy metal limits are expressed in mcg because the relevant quantities are extremely small — a typical lead limit is 5 mcg per daily serving.
LOT number Batch identifier
A unique 8-digit code printed on the bottom of the bottle. Each LOT corresponds to a single production run and a single Certificate of Analysis.
Common questions
Frequently asked questions
What is a Certificate of Analysis (COA)?
A lab-issued document confirming that a specific production batch has been tested against defined safety and quality specifications. It lists the analytes tested, the limits applied, the measured results, the methods used, and the laboratory's accreditation. Every batch of Marek Supplements has one, and they're all published on the Certificates of Analysis page.
Why is the measured amount of an ingredient sometimes higher than the label claim?
Manufacturers typically formulate a small overage above the label claim to compensate for natural degradation across the product's shelf life. A measured potency of 100–120% of label at the time of testing is normal and indicates the product will still meet its labeled dose near expiration. A reading below 90% would suggest under-dosing; above 120% can suggest a formulation problem.
What does "% of allowable limit" mean on a heavy metals test?
Regulatory bodies set maximum daily intake limits for heavy metals like arsenic, cadmium, lead, and mercury. "% of allowable limit" expresses the measured amount as a fraction of that ceiling. A result at 1% of the limit is meaningfully cleaner than one at 80% — both technically "pass," but they are very different in practice. The percentage framing makes the safety margin visible.
What does USP <2232> refer to?
USP General Chapter <2232> is the United States Pharmacopeia standard that sets the permitted daily exposure limits for elemental contaminants — arsenic, cadmium, lead, and mercury — in dietary supplements. It is the same framework used by pharmaceutical manufacturers, and it is the standard Marek Supplements tests against.
Why test a non-grain supplement for gluten?
Gluten cross-contamination can occur in shared manufacturing facilities, in encapsulation aids, or in raw materials processed near grain-derived ingredients. Allergen testing on the finished product verifies that the bottle in your hand meets the FDA's gluten-free threshold of less than 20 parts per million (21 CFR 101.91), regardless of whether grains are formula ingredients. A "Gluten Free" label without finished-product testing is an assumption; the ELISA result is the proof.
What does "< 5 ppm gluten" mean?
Parts per million (ppm) is a measure of concentration: 1 ppm equals 1 milligram of gluten per kilogram of product. The FDA's gluten-free regulation requires fewer than 20 ppm; a measured result of "< 5 ppm" means gluten was undetectable at the assay's lower limit of quantitation — less than a quarter of the regulatory threshold. This is the strongest verification short of dedicated gluten-free facility certification.
Why use two separate laboratories instead of one?
Safety testing and potency testing use different instrumentation, methods, and ISO accreditation scopes. Splitting the work between specialist labs means each test is performed by a facility whose accreditation specifically covers it — and that no single lab is grading its own work. It costs more. It also produces a more credible result.
What does ISO/IEC 17025 mean?
ISO/IEC 17025:2017 is the international standard for the competence of testing and calibration laboratories. An ISO/IEC 17025–accredited lab has demonstrated that its methods, equipment, personnel, and quality controls meet a globally recognized standard for producing technically valid results. Accreditation is granted and audited by bodies like PJLA or ANAB.
Where do I find my LOT number?
The LOT number is typically printed in gold ink on the bottom of the bottle — usually eight digits. Each LOT corresponds to a single production batch and a single Certificate of Analysis. Enter it in the search field on the COA page to pull up your batch's full report.
Is "third-party tested" the same as a published COA?
No. "Third-party tested" can describe a single sample tested at any point in a brand's history. A published, lot-specific COA verifies that the batch in your hand was tested, names the lab, lists the methods, and discloses the actual measured results. The difference is between a claim and a record.
Every batch of Marek Supplements undergoes dual-lab verification with allergen testing. We publish results for every lot because transparency isn't a feature — it's the standard.
Made & Quality Tested in USA Manufactured in a cGMP-compliant, NSF/ANSI 455-2 certified U.S. facility from globally sourced ingredients.