There are two ways to know what is in a bottle. You can trust the front. Or you can read the report for the batch it came from. A lot number is what connects the bottle in your hand to that report. Without it, a lab result is a story about some other bottle.
A lot is one run of the machine
A lot, or a batch, is one production run: one mix of raw materials, on one day, through one set of machines, into a few thousand bottles. Everything in a lot shares the same raw materials, operator and tests. The next lot may come from a different drum, a different supplier, months later.
The lot number is the name of that run. In India the label must carry it, with the date of manufacture and a best-before date. It is usually a short code, inkjet-printed on the bottle. On ours it sits under the best-by date.
The number matters for two reasons. A recall works by lot number, and a bottle without one cannot be recalled. And if a brand tests its batches, each test belongs to a lot number. Type the number from your bottle, get the report back, and that is the report for your capsules. Not a sample. Not last year.
What batch testing means, and what it does not
"Lab tested" on a tub can mean four things. A raw material was tested by the supplier before it arrived. One lot was tested once, at launch. The brand's own lab looked at it, which is a brand marking its own homework. Or every finished lot goes to an outside lab before it ships. Only the last one helps you. Ask a brand which of the four it means. You can usually tell from how long the answer takes.
The test also has to be on the finished product. Testing the ashwagandha powder tells you about the drum. Testing the capsule tells you whether the amount survived the mixing, the filling and the shelf. It costs real money, a few thousand rupees a test, so a full panel on every lot adds up, which is the honest reason many brands test once and print "tested".
The reason to insist is on the record. A 2024 Indian study of 36 protein powders bought off the shelf found about seven in ten mislabelled and one in seven carrying fungal toxins, and the licence numbers on those packs did not stop it. A licence says a business may sell food. A report says what is in this lot.
What a certificate of analysis contains
The report a lab issues is called a certificate of analysis, a CoA. It carries the lab's name, address and accreditation number, on the lab's own letterhead. The sample: product name, lot number, date received, date tested. Then a table with one row per test: the test name, the method, the limit, the result, and pass or fail.
The rows fall into three groups. Identity and potency: is this the thing on the label, and how much is there. A row reads like "vitamin D3, label 15 mcg, found 17 mcg". A little above the claim is normal; FSSAI allows a set overage, roughly 10 to 30 percent depending on the nutrient, so the amount still meets the label at the end of shelf life. A result at 60 percent is a failed batch. A result at 400 percent is a different kind of failure.
Contaminants: heavy metals, meaning lead, arsenic, cadmium and mercury, each on its own line in parts per million or billion, each against a limit. Herbs and minerals pick these up from soil and water, which is why the test is not optional for a botanical. Sometimes pesticides, aflatoxins, residual solvents from extraction.
Microbes: total plate count, yeast and mould, and the named ones, E. coli, Salmonella, Staphylococcus aureus, as counts per gram or "absent in 25 g". For an oil, oxidation: peroxide and anisidine values, which together say how rancid it is. Old oil is what tastes of fish.
And at the bottom, a signature, a name and a date. A report without a signature is a printout.
NABL, and why the letters matter
What makes an outside lab's report worth more than the brand's is accreditation. In India that is NABL, the National Accreditation Board for Testing and Calibration Laboratories, which checks that a lab can actually run the tests it claims to, to the international standard ISO/IEC 17025, and rechecks on a schedule. FSSAI keeps its own list of recognised food labs, and the serious labs are on both.
Accreditation is per test, not per building. A lab accredited for microbiology may not be accredited for heavy metals, so the question is not "is this lab NABL" but "is it NABL for the rows on this page". You can check a lab's number and scope on the NABL site.
Since 2021 NABL has also required a QR code on every accredited report. Scan it and you reach the lab's own record, which is how you know the page has not been edited on the way to you.
Why a badge is not a report
A website badge is a picture. "Third-party tested". "Lab verified". "GMP certified". It takes one afternoon and no lab to add one to a page. A report has a lab's name, a date, a lot number and a column of numbers, and every one of those can be checked. The badge asks you to trust. The report lets you look.
The same goes for the phrases near it. "GMP certified" describes how a factory runs, which is worth something, and says nothing about your lot. "ISO certified" is about paperwork. "FSSAI approved" is not a claim a brand is allowed to make at all. "Clinically studied ingredient" means someone studied that ingredient, usually at an amount the label may not match. A QR code on the pack is the newer habit, and a good one, as long as it opens the lab's report for that lot and not a page of badges.
What to check on your label
- A lot or batch number printed on the bottle itself, not on a peel-off sticker.
- Date of manufacture and best-before, next to the lot.
- A way to get the report for that lot: a page, a code, an email address.
- The report on the lab's letterhead, dated after the manufacture date, with an NABL number you can look up and the lab's QR code.
- Each active ingredient found at or a little above the label claim.
- Heavy metals and microbes shown as numbers against limits, not the word pass on its own.
- A signature and a date on the report.
Then read ours the same way: see the label
