Do third-party tested supplements cost more?

Usually, yes. We can make 28 comparisons. Each is one format, and one labeled strength where a category is compared by strength, in which a certifier names a package we price beside others like it. In 25 of them, the cheapest certified package costs more than the cheapest one there: 1.07× to 5.7× as much per dose. In 3, the cheapest certified package is also the cheapest there. In 4 more, the certified package is the only one we price at its format and strength, so there is nothing to set it against. In 8 categories, nothing we track is certified at its package, so there is no certified price to compare.

Certified here means a certifier's own scope covers the exact package sold: NSF names package sizes on each listing, and USP names the product and puts its mark on the label, so a USP row counts when both are true. Across all 568 products we track, 112 clear that bar. It says an outside program tested that product for what the program tests for. It does not mean a cheaper product is unsafe, and neither column says anything about whether a supplement will work for you.

Each category gets one row in the table. Where a certifier names a package we price, the row is the format and strength we price the most packages in among those holding one; where nothing is certified, it is the format and strength with the most packages. Which one is chosen by count, never by price. Every format and strength counted above is listed under the table. Both columns are shelf prices per comparison dose before delivery, measured the same way, so a category page's pick, which also needs a published delivery rate, can be a different product. The second figure in each cell is that price over thirty comparison doses, one a day, which is a way to read the first figure and not a suggestion of how much to take.

Every format and strength counted above, 32

These 32 lines are 28 comparisons and 4 certified packages, each the only one we price at its format and strength. There is one line for each format, and each labeled strength where a category is compared by strength, in which a certifier names a package we price. 16 are not in the table above. Prices are per comparison dose, before delivery.

3 vitamin D products sit outside the strength bands this site ranks (below 400 IU or above 10,000 IU per serving) and are left out of the vitamin D rows. Products above 10,000 IU are sold as weekly or monthly doses, so the site never gives them a cheapest claim.

Each category's own “which brands are third party tested” page splits the rest into listed at another size, searched and not found, and not settled either way.

Related: the cheapest NSF certified creatine, per 5 g, and is Thorne creatine worth the price?

Every category we compare: the home page. Every question we answer: the question index.

What this rests on: prices we last recorded at the retailer named on each product page, which go stale, and each page says when it was checked; the products we track, not every product sold, and Amazon and Walmart are not among the stores; listings and labels read at the source, each linked from the page. Found an error? Tell us. The full method: How we compare.