Is Kirkland Signature third-party tested?

Last reviewed July 2026.

Yes — but it's a different kind of yes, and the difference matters. Kirkland Signature fish oil is USP Verified (USP's verified products list ↗, checked 2026-07), covering Fish Oil 1000 mg (the Costco staple, ~250 mg EPA+DHA per softgel). USP is a real, independent program: it tests the product and audits the factory on an ongoing basis.

Kirkland fish oil is NOT in the IFOS database — the mark on the label is USP Verified, a genuinely independent program (testing plus factory audits). The catch: USP publishes a pass/fail mark, not per-batch EPA/DHA measurements, so there are no public numbers to put in a ranking.

USP Verified vs IFOS: mark vs measurements

USP publishes a pass/fail mark — "what's on the label is in the bottle". IFOS publishes the measurements themselves: EPA and DHA per serving as a lab measured them, TOTOX freshness, heavy metals, per lot. Both are independent. Only one produces numbers you can compare across brands — which is why our cost-per-gram ranking is built from IFOS-style batch reports, and why a USP-verified oil can be a fine product that still can't be ranked on published data.

If you want the products where the actual numbers are public, the ranking covers every fish oil whose batch report we've read, sorted by cost per gram of measured EPA+DHA. Background: what "third-party tested" really means.

This page summarizes published third-party testing data and makes no health, benefit, or treatment claims. A certificate describes one tested batch, not a permanent grade.