NSF, USP, Informed Sport: what testing seals check

Here’s something most people don’t know: nobody checks a supplement before it goes on sale. The FDA doesn’t approve supplements or their labels first. Whether the capsule holds what the label says is up to the maker – unless an independent lab checks it. That’s what a testing seal stands for.

What the law requires – and what it doesn’t

Every US supplement maker has to follow “good manufacturing practice” (GMP): they must test each batch themselves for identity, purity and strength (FDA (opens in a new tab)). The FDA inspects factories now and then, but it doesn’t approve products or labels before they’re sold (FDA (opens in a new tab)). So “made in a GMP facility” on a bottle describes the legal minimum, not an extra check.

The seals, side by side

These are the seals we found most often on the products we checked:

The difference that matters most: NSF Certified for Sport and Informed Sport also test for substances banned in sport – that’s why athletes look for them. The others focus on whether the label is right and whether there are contaminants. IFOS is only for fish oil.

Where you find seals

Seals are most common in sports supplements and fish oil – that’s where athletes and testing programs meet. For most vitamins, herbs and minerals, a seal is rare.

What a seal costs

+22%

typical cost per dose with a seal vs. without, same supplement

9 of 30

supplements where products with a seal are cheaper

We compared the middle price per dose with and without a seal in the 30 supplements that have at least five of each. A seal usually costs extra – testing isn’t free – but not always. In creatine, for example, you can filter the list for NSF Certified for Sport and still sort by price. More on price and quality in our guide on whether paying more gets you more.

“Third-party tested” without a name

Some labels say “third-party tested” but don’t name the lab or the program. That can be true – but you can’t look it up. In our quality score it counts for half of what a named seal gets.