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This warning is legally required by the state of California for dietary supplements and many other products sold in that state which expose you to levels of one or more chemicals that may cause cancer or reproductive harm. The list of chemicals which can trigger a warning includes hundreds of compounds but, unfortunately, the California law (known as Prop 65 or the Safe Drinking Water and Toxic Enforcement Act of 1986) does not require businesses to say exactly which compound is the reason for the warning.

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. generally applies the Prop 65 limits when testing for contaminants in supplements.  In's experience testing thousands of supplements, it has identified many which exceed the California limit for lead, a heavy metal, 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. has typically found that products which exceed the limits for lead contamination pose a greater risk to children and to women who are pregnant or nursing than to other healthy adults but, nevertheless, they represent easily avoidable sources of these toxic compounds. has also found that manufacturers are often 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.

Although California is the only state requiring this labeled warning, companies that sell products nationally sometimes include the label on products sold even outside of California. 

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'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.

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July 10, 2019

I bought Jarrow beef bone powder and it made me tired all the time. Exhausted in fact. As soon as I stopped I was fine. I thought you should know.

September 22, 2018

I am surprised some companies are either lazy or do not want to tell the whole truth, when they add text "prop 65" hidden in small print on bottles, yes only those 4 letters and 2 numbers without any explanation.

It would be much more consumer friendly to put a small paper inside every supplement bottle with a certificate of analysis for that batch, with contact information to a 3rd party lab, with comparisons to federal limits or Pharmacopeia limits.

Or a QR bar code that leads to a 3rd party website with certificate of analysis for that batch.

February 20, 2019

There are 900+ chemicals listed in California's Prop 65 rules it would be impossible and cost prohibitive to check a product for all of them. Further, the standards are ridiculous and again, nearly impossible to prove the amount of exposure exceeds what is laid out. So to avoid being sued by the bounty hunter law firms of which themselves are a complete racket, companies label their product with the overall label allowed by California. Take a walk though Disney Land in CA. You can't walk 20 feet without seeing another Prop 65 warning sign. Sawdust is on the list. Aspirin is on the list, can go on and on....

January 12, 2020

This is why I voted against this proposition (and others like it). This warning is on every door to every store. It’s less helpful and less noticeable than “exit” signs.

It may even be on every building due to simple CYA. An office building may have new carpeting or occasionally need to unclog a drain with Draino so they put up the warning.

This warning has absolutely zero effect within CA. If I were selling something, I would put the warning on my product just in case. Even if I had no reason to think my product had any cancer causing properties, I don’t want to have every item certified. So... just in case, I will indemnify myself.

June 25, 2021

Thanks, Nancy18843. That's my impression, too.

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