Why Is There a California Prop 65 Warning on My Supplement?

Answer:

What is a California Prop 65 warning?

A warning, known as the Prop 65 warning, is legally required by the state of California on dietary supplements and other products sold in that state that expose you to levels of one or more chemicals that may cause cancer or reproductive harm. The list of chemicals that require a warning includes hundreds of compounds, including lead, cadmium, arsenic, and mercury. Some companies that sell products nationally may include a Prop 65 warning even on products sold outside of California.

The California law (known as Proposition 65, or the Safe Drinking Water and Toxic Enforcement Act of 1986) does not currently require businesses to say exactly which compound is the reason for the warning, which can leave a consumer confused. To help remedy this, the law was amended in 2024 (California OEHHA 2024) to require companies to identify at least one chemical for which the warning is being issued on a supplement. However, companies have until January 2028 to include this additional information in the warnings.

ConsumerLab.com has found that manufacturers are sometimes not aware that their product exceeds a Prop 65 limit and do not include a warning on the label, even when the product is sold in California.

Does ConsumerLab use Prop 65 limits?

California's limits are strict and, in many cases, go beyond any federal limit — particularly as the federal government has not established limits on contaminants in supplements, leaving that decision up to each manufacturer.

ConsumerLab.com generally applies the Prop 65 limits when testing for contaminants in supplements and foods. In ConsumerLab.com's experience testing thousands of supplements, it has identified many which exceed the California limit for the heavy metals lead, cadmium, and or arsenic which can occur in plant-based ingredients, such as herbs, as well as in minerals. Often these ingredients are not the primary ingredient in a product, but are part of a blend or proprietary formula added to enhance the product or distinguish it in the marketplace.

ConsumerLab tests have also revealed many foods, including certain cocoa and dark chocolate products, whole and ground flaxseeds, and sunflower seeds and butters, exceed strict the California limits for one or more contaminants (see which foods and supplements tested by ConsumerLab frequently contain heavy metals.) Additional allowances beyond the strict Prop 65 limits have been permitted by California courts for categories of products in which heavy metals are inherent, and ConsumerLab provides similar allowances (see How Products Are Evaluated).

Prop 65 warnings as legal protection?

In an effort to protect themselves from potential lawsuits in California for not displaying a required warning, some companies may affix the Prop 65 warning labels to products -- as well as to website pages about products -- regardless of whether or not the specific products exceed Prop 65 limits.

If you see a warning label of this type, you may want to check ConsumerLab.com's website to see if there is information about the product. You may also want to contact the manufacturer or distributor to learn the reason for the warning.