California Prop 65 for Supplement Brands: What You Need to Know

What Prop 65 Is

Prop 65 maintains a list of over 900 chemicals known to the State of California to cause cancer, birth defects, or reproductive harm. The list is updated regularly by the Office of Environmental Health Hazard Assessment (OEHHA).

The law has two provisions. First, businesses may not knowingly discharge listed chemicals into drinking water sources. Second, businesses must provide a "clear and reasonable" warning before exposing anyone to a listed chemical. The second provision is the one that affects supplement brands.

Prop 65 does not ban products or set product standards. It requires warnings. A product with lead above the safe harbor level is legal to sell, as long as it carries a Prop 65 warning. A product without a warning that exposes consumers to a listed chemical above the threshold is a violation.

Why Prop 65 Matters Outside California

Many brand owners assume Prop 65 is a California-only issue. That assumption is wrong and expensive.

• E-commerce reaches California. If you sell online and don't block California shipments (almost nobody does), Prop 65 applies. Amazon, Shopify, and every major e-commerce platform ship to California by default.
• National retailers require compliance. Amazon, Walmart, Target, Costco, and Whole Foods all require Prop 65 compliance or warnings as a vendor requirement. It's in the supplier agreement.
• Plaintiff attorneys monitor nationally. Prop 65 bounty hunter firms test products purchased from anywhere that ships to California. They don't care where your company is based. They care whether your product contains listed chemicals without a warning.
• Other states are watching. Several states have proposed or enacted similar chemical warning laws. Building Prop 65 compliance into your process now prepares you for future regulations.

Chemicals Most Relevant to Supplements

Of the 900+ chemicals on the Prop 65 list, a handful appear regularly in dietary supplement testing. Heavy metalsHeavy Metals TestingTesting for toxic metals (lead, mercury, arsenic, cadmium) in supplements. are the primary concern because they occur naturally in soil, water, and plant-based ingredients.

Testing and Compliance Options

You have two paths to Prop 65 compliance. Most brands use a combination of both, depending on the product and the specific chemicals involved.

For guidance on what testing to expect from your manufacturer, see our supplement testing requirements guide. For understanding test results, see our guide to reading a COA.

Warning Label Requirements

Since August 2018, Prop 65 warnings must follow OEHHA's "clear and reasonable" warning regulations. The old generic warnings no longer satisfy the requirement.

What a Compliant Warning Includes

• ✓The word "WARNING" in bold, uppercase letters
• ✓A black exclamation point inside a yellow triangle (the warning symbol)
• ✓The name of at least one listed chemical in the product
• ✓A statement that the chemical is known to cause cancer, birth defects, or reproductive harm
• ✓The URL: www.P65Warnings.ca.gov

Where the Warning Must Appear

For products sold in stores, the warning must appear on the product label. For e-commerce, the warning must be displayed on the product listing page before the point of purchase. Amazon has specific fields for Prop 65 warnings in product listings. If you sell on your own website, the warning should appear on the product page, not buried in terms and conditions.

Common Prop 65 Mistakes

• Assuming it doesn't apply because you're not in California. Any product sold to California consumers is covered. Online sales count. National retail counts. If your product can reach California, Prop 65 applies.
• Using an outdated warning format. The 2018 regulations changed the required warning format. Old-style generic warnings ("This product contains a chemical known to the State of California...") without naming the specific chemical are no longer compliant.
• Testing only finished product and not raw materials. If your ingredients have high heavy metals before blending, the finished product will too. Test incoming raw materials to catch problems before production. This also gives you leverage with ingredient suppliers.
• Not testing every batch. Natural ingredients vary. One batch of turmeric may have low lead. The next batch from a different growing region may not. Batch-level testing is the only way to know.
• Ignoring e-commerce warning requirements. A warning on the physical product is not enough. E-commerce platforms require the warning on the product listing before purchase. Missing the online warning is as much a violation as missing the physical one.
• Waiting for a lawsuit to take action. Prop 65 settlements average $30,000 to $100,000+. Annual testing costs $1,000 to $3,000. The math favors prevention. Plaintiff firms specifically target brands without warnings.

Getting Started with Prop 65 Compliance

Prop 65 compliance does not require a lawyer for every step, but it does require a systematic approach.

• ✓Identify which Prop 65 chemicals are relevant to your product. Heavy metals are the default concern. Botanical ingredients may trigger additional chemicals on the list.
• ✓Add heavy metals testing to your finished product testing protocol. Request lead, cadmium, arsenic, and mercury on every COA.
• ✓Compare results against OEHHA safe harbor levels. Your calculation must account for the recommended daily serving size (exposure = concentration times serving size).
• ✓If levels are below safe harbor: document your testing and keep records. If levels are above: add a compliant Prop 65 warning to your label and e-commerce listings.
• ✓Review your ingredient sourcing. Brands that control ingredient quality upstream have an easier time staying below Prop 65 thresholds.
• ✓If you sell on Amazon, complete the Prop 65 fields in your product listing. Missing these fields can trigger listing deactivation.

For a broader view of compliance risks, see our supplement compliance risks guide. For label requirements beyond Prop 65, see our packaging and label compliance guide.