First things First. HormoneSynergy® Inc is very small business consisting of 3 employees and  exempt from the requirements of Proposition 65.
That said ALL of our Manufacturers (both Brand Name and HormoneSynergy® / RetzlerRx™ Private label) are in compliance with California Prop 65. 


If you live in the state of California and have ever purchased dietary supplements from ours or other websites, you might have noticed a warning label indicating the presence of chemicals linked to cancer, birth defects, or other reproductive harm on the supplement label.

This warning label is known as California Proposition 65, commonly referred to as Prop 65 for short, and it’s commonly displayed on a range of products from furniture to dietary supplements. Although this warning may be disconcerting, it’s important to understand the basics of Prop 65 and how its guidelines relate to dietary supplements. Read on to learn more about prop 65 warning on supplement labels and what it means for supplements and beyond.

What is Proposition 65?

Proposition 65, also known as the Safe Drinking Water and Toxic Enforcement Act of 1986, is a California law that requires companies to display a warning label on any product containing certain chemicals with levels above a predetermined threshold. (6)

Prop 65 does not restrict the sale of products containing harmful chemicals, its purpose is to inform consumers about the potentially hazardous contents of the products they’re purchasing. The Prop 65 list is continually updated with new additions based on the most recent research and occasionally delists existing chemicals that are no longer considered to be a concern to consumers. (7)

Where is the Prop 65 warning label required?

The Prop 65 warning label is required on many products we use and are exposed to every day. Examples of common products requiring this label include:

  • Alcoholic beverages
  • Dietary supplements
  • Furniture
  • Petroleum products (e.g., crude oil, diesel fuel, gasoline)
  • Wood products (10)
Additionally, some physical locations are required to post Prop 65 warning signs:
  • Amusement parks
  • Apartment buildings and rental properties
  • Dental offices
  • Designated smoking areas
  • Gas stations
  • Hotels
  • Office buildings
  • Parking garages
  • All Restaurants and coffee shops (10)

What does it mean if a product has a Prop 65 warning label?

Products labeled with the Prop 65 warning contain certain levels of one or more chemicals known to cause cancer, birth defects, or other reproductive harm. (6)
By law, a business must include a warning label if their product contains a chemical known to cause cancer unless the amount is minimal enough that it poses no significant risk. “No significant risk” means that the likelihood of developing cancer is no more than one in 100,000 over the course of a 70-year lifespan as a result of the chemical exposure. (3)

Chemicals known to cause birth defects or other reproductive harm, undergo thorough research to determine the level at which the chemical poses no threat to humans or animals . This level is known as the “no observable effect level”. Out of an abundance of caution, Prop 65 divides this level by 1,000 to ensure an adequate margin of safety. In other words, a warning label is required if the product contains more than 1/1000th of the “no observable effect level” for a particular chemical known to cause other reproductive harm and birth defects. (3)

The Office of Environmental Health Hazard Assessment (OEHHA) is responsible for reviewing and evaluating current scientific evidence to determine whether or not a chemical should be included in the list of chemicals in Prop 65. 

Chemicals of concern

Approximately 900 chemicals, some naturally found in nature and others man-made, are included on Prop 65’s list. Examples of these chemicals include: 

  • Arsenic
  • Asbestos
  • Benzene
  • Bisphenol A (BPA)
  • Cadmium
  • Carbon monoxide
  • Glyphosate
  • Lead
  • Nitrous oxide (11)

For a complete list of chemicals, visit California’s Proposition-65 website

What does the California Prop 65 warning label look like?

Products containing certain chemicals with levels above a predetermined threshold are required to carry a Prop 65 warning label similar to the example below. 

prop 65 warning label examples
Prop 65 warning labels may also include the name of the specific chemical found in the product.

Manufacturers are also required to indicate the name of the chemical or chemicals contained in any product produced after August 30, 2018. If a product was produced before August 30, 2018, they are not required to include the chemical as long as the company meets all requirements determined at the time of manufacturing. (9)

What are the benefits of Prop 65?

The primary objective of Prop 65 is to reduce harmful chemical exposure in California. Information provided in Prop 65 warnings allow individuals to make informed decisions about the products they purchase, helping them reduce their exposure to potentially harmful chemicals. (3)

As a result of Prop 65, many businesses have entirely removed harmful chemicals from their products. Several other improvements have been made in the state of California including reductions in harmful air emissions, decreased lead content found in jewelry and many personal care products (e.g., toothpaste, hair dye), and reductions in arsenic levels found in bottled water. (8)(12)

Are products labeled with a Prop 65 warning dangerous?

Not necessarily. When used as directed, chemical exposure is minimal. (4) Chemical exposure does not necessarily mean a particular product will cause cancer, birth defects, or other reproductive damage.

Prop 65 guidelines are much more rigorous than many of the Environmental Protection Agency’s (EPA) and the U.S. Food and Drug Administration’s (FDA) guidelines for chemical exposure. For example, the EPA’s limit for lead in drinking water is 15 mcg/L, while the Prop 65 threshold for any product containing lead is 0.5 mcg. (2)(5) The FDA’s limit for daily lead exposure, also known as the Interim Reference Level (IRL), is 12.5 mcg per day. (18)

For further perspective, many foods naturally contain levels of heavy metals commonly found in soil and water and are exempt from Prop 65 regulations. (15) Dark chocolate, for example, contains an average of 0.92 mcg of lead per ounce, which exceeds Prop 65 guidelines. (14) Additionally, grape juice contains approximately 2.6 mcg of lead per serving, which is over five times the limit advised by Prop 65. (16

What does a Prop 65 warning on supplements mean?

Unlike food, supplements containing certain chemicals are required to carry a Prop 65 label even if all ingredients in a dietary supplement are naturally occurring. Heavy metals, including arsenic, cadmium, lead, and mercury, are prevalent in the soil and water. These metals can then accumulate in plants commonly used in the production of dietary supplements. (13)
Most vegetable, fruit, and herbal matter is likely to contain some level of contaminants, whether that’s from pesticides, herbicides, or heavy metals. (17) Keep in mind that the level of exposure to these substances is minimal and average daily intake is well below the tolerable limits determined by the EPA and FDA. (1)

The supplement brands provided on HormoneSynergy Online Store take precautions to ensure the safety of their products. You may notice some of your supplements carry a Prop 65 warning label on the packaging and this is a clear sign that the manufacturer is compliant with California law. The warning label simply means that the supplement contains trace amounts of certain chemicals that may pose a small risk. 

The bottom line

While receiving a product with a Prop 65 warning label may cause alarm to California residents (the only state requiring this more rigorous standard), chemical exposure is generally low when products are used as directed.

California Prop 65 regulations are particularly stringent and exceed guidelines established by the EPA and FDA.

Use supplements as directed and speak to your integrative healthcare practitioner if you have any concerns. 

*These statements have not been evaluated by the United States Food and Drug Administration. HormoneSynergy supplements are not meant to be taken as an alternative to prescription medications recommended by your physician. If you are seeking to replace any pharmaceutical medication with any of our products we recommend that you do so only after consulting your healthcare provider. *You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you. This product is not intended to diagnose, treat, cure or prevent disease. The information provided about this or any HormoneSynergy nutritional supplement or any information contained on or in any product label or packaging is for informational purposes only and is not intended as a substitute for advice from your own physician or health care professional. You should always consult with a licensed healthcare professional before starting any diet, exercise or supplementation program, before taking any medication, or if you have or suspect you might have a health problem. As with any nutritional supplement do not take if you are pregnant or nursing or while taking medications without consulting your healthcare practitioner.