NOW Testing Reveals Potency Failures in Oregano Oil on Amazon, Raising Quality Concerns in Supplements

NOW has released new internal and third-party testing data pointing to significant quality and labeling inconsistencies in oregano oil dietary supplements sold on Amazon. The results highlight broader concerns about transparency and supply chain accountability within the nutraceutical industry, an April press release from the company explains.¹

Product Testing and Results

The company evaluated 35 oregano oil products—two bottles of each product purchased in February 2026—including NOW’s branded product, using both in-house analytical methods and independent verification from ISO 17025-accredited laboratory Eurofins. According to the findings, nearly two-thirds of tested products failed to meet their labeled potency for carvacrol, the primary bioactive compound associated with oregano oil’s functional benefits. Notably, six products contained no detectable levels of carvacrol.

Testing was conducted using high-performance liquid chromatography (HPLC), a method selected for its specificity in isolating and quantifying carvacrol particularly in the presence of structurally similar compounds such as thymol. Of the 35 products tested, only 14 met their labeled claims for carvacrol, and fifteen products delivered less than 8% of their stated carvacrol content.

Oregano oil, derived from Origanum vulgare, is commonly positioned for its role in supporting intestinal flora balance, NOW explains. Its efficacy is closely tied to carvacrol content, which typically ranges between 55% and 90% in properly standardized oils.

NOW’s own oregano oil products, in both softgels and liquid formats, were among those that met or exceeded labeled carvacrol claims in the analysis.

The Importance of Validated Testing Methods

The product testing highlighted methodological concerns that may contribute to inflated potency claims in the marketplace, NOW notes. Non-specific analytical approaches, such as spectrophotometric assays, can misidentify or overestimate carvacrol levels due to interference from other constituents, the company explains. In contrast, chromatographic methods like HPLC provide more reliable differentiation.

In addition to analytical variability, NOW suggested that manufacturing practices may be a contributing factor. A preliminary review of product labeling and presentation indicated that many of the tested supplements may originate from a limited number of contract or private-label manufacturers. This raises questions about product testing across brands and the supply chain. While contract manufacturers play a central role in production, brand owners, distributors, and retailers are equally accountable for ensuring product quality and compliance, NOW stated.

According to company leadership, the results reflect ongoing challenges in maintaining quality consistency in a rapidly expanding e-commerce environment. “This round of testing was disappointing, with nearly two-thirds of the brands failing carvacrol testing,” stated Katie Banaszewski, NOW Senior Director of Quality. “NOW’s in-house analytical testing paired with Eurofins’ independent verification underscores the importance of scientifically valid methods. NOW will continue to purchase and test products sold on major online platforms and publicly share the results to encourage higher quality standards across the supplement industry.”

Product Testing in the Industry

As consumer demand for botanical supplements continues to grow, the study underscores the need for robust analytical validation, transparent labeling, and stronger oversight throughout the value chain to ensure product integrity.

In the past few years, NOW has conducted multiple product test similar to this one. In November 2025, the company announced results from testing 22 St. John’s Wort (Hypericum perforatum) products on Amazon, finding that only NOW’s product passed the potency testing. Additionally, synthetic dyes were found in nine products, highlighting how certain testing methods can misrepresent dyes and lead to artificially inflated potency results. A validated reverse-phase High-Performance Liquid Chromatography (HPLC) method was used to test the products.

This article was created with assistance from AI. The content has been reviewed and edited by Erin McEvoy, Associate Editor. For more information on the extent and nature of AI usage, please contact us.

References

1. NOW. NOW Tests Oregano Oil Supplements Sold on Amazon. Published April 2, 2026. Accessed April 2, 2026. https://www.nowfoods.com/healthy-living/articles/now-tests-oregano-oil-supplements-sold-amazon
2. McEvoy E. NOW’s potency testing finds only one St. John’s Wort supplement passed. Published November 7, 2025. Accessed April 2, 2026. https://www.nutritionaloutlook.com/view/now-s-potency-testing-finds-only-one-st-john-s-wort-supplement-passed