Nobody checks what is in a supplement before it is sold

A 1994 law put dietary supplements outside the approval system that governs medicines. The manufacturer decides what goes in, and the FDA can generally only act after somebody is harmed.

Written by KenyRx · Updated August 31, 2026

Written from published research and federal data. Not medically reviewed.

Key takeaways

Under DSHEA (1994), supplements need no pre-market approval — no proof of effect, and no proof of the dose on the label.

The FDA’s power is largely reactive: it acts once a product is already on shelves and already causing harm.

Independent testing repeatedly finds products with more, less, or none of the labelled ingredient — and some containing undeclared prescription drugs.

A prescription generic has been through the opposite process: proven ingredient, proven dose, inspected factory. That is what the low price is buying.

Most people assume that anything sold in a pharmacy has been checked by somebody. For medicines that is true and the checking is extensive. For the supplement aisle a few feet away, it mostly is not.

The law that carved supplements out

The Dietary Supplement Health and Education Act of 1994 placed dietary supplements in their own regulatory category, closer to food than to drugs. A manufacturer does not have to prove to the FDA that a supplement works before selling it, and does not have to prove that the amount on the label is the amount in the capsule.

A new drug arrives the other way round. It has to demonstrate efficacy and safety in controlled trials before anyone can buy it, and the factory making it is inspected.

The FDA mostly acts after the harm

Because there is no approval step, the agency's main power over supplements is reactive: it acts once a product is already on shelves, usually once there is evidence of harm or of illegal content. Its own public list of tainted products marketed as supplements runs to hundreds of entries, many containing undeclared prescription drugs.

After, not before

For medicines the burden of proof falls on the manufacturer, before sale. For supplements it effectively falls on the regulator, after sale.

What testing finds in the bottles

When independent laboratories buy supplements off the shelf and analyse them, they repeatedly find products containing substantially more or less of the labelled ingredient than the label claims, and some containing none of it. Red yeast rice is the sharpest published example — analyses have found its active compound varying roughly a hundred-fold between brands — but it is not unusual in kind.

This is not necessarily fraud. A plant preparation genuinely varies with the crop, the growing conditions and the extraction. That is precisely the problem a pharmaceutical manufacturing standard exists to remove.

The other side of it

Not every supplement company is careless, and some submit voluntarily to third-party verification. The point is not that all of them are bad; it is that the label alone does not distinguish the careful ones from the rest, and you are being asked to guess.

What a generic went through instead

A generic tablet has to contain the stated ingredient at the stated dose, be shown to behave in the body like the original drug, and come from an inspected facility. That process is the reason a generic is trusted, and it is worth setting against the price, because the price is usually low. The regulation is what you are paying for, and it costs very little.

Sources

These pages describe what the published evidence shows, attributed to the sources above. Where a remedy has been tested and works, that is said; where it has been tested and does not, that is said too. Nothing here recommends taking or stopping anything, and none of it is medical advice.