Third party testing answers 4 separate questions, and the panel behind each one runs 3 to 6 weeks, and one certificate rarely covers all of them: identity, potency, heavy metals and microbes. A panel reporting 95 percent purity tells you nothing about lead at 0.5 ppm. A heavy metals screen tells you nothing about whether the powder is mastic at all. Ask which question the paperwork answers before you treat it as proof.
Mastic gum is a resin from a specific tree on one Greek island, which makes identity the first thing worth verifying. Substitution with cheaper resins is the classic failure mode, and a certificate that only lists a purity percentage can't catch it.
What third party testing actually checks
Identity testing confirms the material is what the label says, usually by comparing the sample against a reference standard in a 300 mg specimen. Potency measures how much of the active compound sits in each 500 mg capsule. Heavy metals screening covers lead, arsenic, cadmium and mercury, the 4 that matter in botanical extracts, and a useful report states each one in ppm against a stated limit. Microbial testing covers total plate count, yeast, mould and the specific pathogens that trigger recalls.
Four panels, four separate line items, and a supplier can order any one of them. "Tested" on a product page usually means at least one. It rarely means all four.
The questions to ask before you buy
Which batch number was tested, and does the certificate match the lot on the bottle you're holding? Batch level matters because testing one run in 2023 says nothing about the 20 kg lot that shipped this spring. If the answer is a generic 1 page certificate with no lot number, that's the answer.
Ask which lab, which batch, and which four things. A brand that can answer all three in one email has done the work.
Which laboratory ran the panel, and when? Independent labs publish their accreditation, and a report should name the method and the date the sample was received. A certificate with no lab name, no date and no batch reference is a marketing document rather than an analysis.
Ask how often the brand re-tests. Every 1 of 1 lots is the standard worth paying for. Once a year, or once at formulation, means the document describes a product that may no longer exist in that form.
Why verification is voluntary
In most of the market, third party testing isn't legally required before a supplement reaches a shelf. The manufacturer is responsible for safety, and the regulator checks after the fact rather than before. That's why brand behaviour varies so widely on the same product category.
Some companies test every lot and publish certificates by batch number. Others test once at formulation and never again. Both can print "lab tested" on the front of a jar, and the phrase carries no defined meaning.
What a certificate does not cover
Testing confirms what's in the batch. It doesn't confirm the ingredient does anything for you, and it doesn't cover the finished product's behaviour in your body. Those are separate claims with separate evidence, and certificates get used to imply them far too often.
It also doesn't cover storage. A batch that passed microbial testing in March can fail after six months in a steamy bathroom cupboard, because the certificate describes the product at the moment of testing.
So the practical version: ask for the lot number, the lab name and the date, and check that heavy metals and microbes are both on the panel. If a brand can produce that, it has done more than most. If it can't, the price is usually the honest signal, and mastic gum sold at 30 percent of the going rate is a good place to stop and ask why. A typical 100 capsule supply runs $18 to $30, so anything under $12 deserves that question.
Frequently asked questions
What does a certificate of analysis cover?Show answerHide answer
Whatever assays were ordered. Ask which were run before assuming anything.
Is testing legally required?Show answerHide answer
Verification is voluntary in most of the market, which is why brands differ so much.
What should I ask a brand?Show answerHide answer
Which batch was tested, by which lab, and for which four things.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
