The Basics of Reading COA (Certificate of Analysis) Documents

A Certificate of Analysis verifies a product batch's tested composition. This post explains what a COA typically includes and how to read one.

What a COA Is

A Certificate of Analysis (COA) is a document that reports the test results for a specific batch, or lot, of a product. It shows what was tested, the method used, the specification (the acceptable range) and the actual result. COAs are used throughout the supply chain: suppliers provide them for raw materials, and many supplement brands publish them for finished products.

The Main Sections

1. Header Information

• Product name and description.
• Lot or batch number: match this to the number printed on your bottle.
• Manufacture date and expiration or retest date.
• Lab name: who did the testing, and whether it's in-house or an independent third party.

2. Test Results Table

This is the core of the COA. Each row usually lists:

• Test or parameter: what was measured, such as appearance, identity, assay or heavy metals.
• Method: how it was measured, such as titration, ICP-MS or a USP method.
• Specification: the acceptable range or limit.
• Result: the actual measured value.
• Pass/Fail or "Conforms."

3. Sign-off

A quality-control signature and date confirm the results were reviewed and the batch was approved.

Key Tests for an Iodine Product

• Appearance: color and clarity match the specification.
• Identity: confirms the product contains iodine.
• Assay: measures strength, often expressed as a percentage of the label claim. See The Basics of Titration.
• Heavy metals: lead, arsenic, cadmium and mercury, with results below set limits.
• Microbial tests: where relevant for the product type.

Reading Results Like a Pro

• "< LOQ" or "ND": "below limit of quantitation" or "not detected" means the amount was too small to measure, which is the result you want for contaminants.
• Units: contaminant limits are often in parts per million (ppm) or parts per billion (ppb).
• Percent of label claim: an assay result near 100% means the product closely matches the label.

Red Flags

• No lot number, or a lot number that doesn't match any bottle.
• No testing lab named.
• Missing specifications, so results can't be judged.
• A COA that hasn't been updated in years for a product sold continuously.

Where to Find Ours

Lugol's Original's publishes Certificates of Analysis for its iodine products. For more on how testing works, see How Iodine Solutions Are Tested for Purity and What Does USP Grade Mean?

Frequently Asked Questions

Do I need a COA for every bottle I buy?
No, but it's worth knowing a brand publishes them. Comparing the lot number on your bottle with a posted COA shows how that specific batch tested.

Should I talk to a doctor before starting?
Yes. Anyone considering a new supplement — especially one involving iodine — should check in with a healthcare provider first, particularly if pregnant, nursing, or managing a thyroid condition or thyroid medication.

Where can I read the full picture on using this product day to day?
See our complete guide to Lugol's Solution usage and protocols.

Shop Lugol's Solution — the traditional, trusted way people have supported their iodine intake for over 200 years.

Lauren Mitchell covers comparisons, formats, and quality questions for the Iodine Journal.

This article is for general educational purposes only and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease, and is not a substitute for advice from a qualified healthcare provider — especially if you are pregnant, nursing, taking thyroid medication, or managing a thyroid condition.