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  1. Natural Toxins in Food

Blue-Green Algae Products and Microcystins

Blue-Green Algae Products and Microcystins

Blue-green algae are a unique type of bacteria, also known as cyanobacteria, that grow in water. Certain blue-green algae grown in freshwater lakes and aquaculture ponds are used in dietary supplements and as an ingredient or color additive in other foods. One commonly used type is AFA (Aphanizomenon flos-aquae), which is wild harvested from Upper Klamath Lake in Oregon.

Other types of cyanobacteria, such as Microcystis species, can sometimes grow in the same lake as AFA. These cyanobacteria produce natural toxins called microcystins, which can present health risks. If companies do not test for microcystins, the AFA they harvest could inadvertently be contaminated with these toxins.

The FDA seeks to protect consumers from microcystins by working with industry, testing food products when contamination is suspected, doing research, and providing information to consumers.

On this page:

What the FDA Does About Microcystins in Dietary Supplements and Other Foods

As part of our mission to protect the public health, the FDA works to prevent dietary supplements and other foods with unsafe levels of microcystins from entering the food supply and removes them from the market when unsafe levels are detected.

Determining the health and safety risk. We assess the public health and safety risk of microcystins in dietary supplements and other food products on a case-by-case basis. The World Health Organization (WHO) and the U.S. Environmental Protection Agency (EPA) have established provisional guidelines for the amount of microcystins a person can be safely exposed to daily. We use this information, along with information on the amount of microcystins we find in a product and how much of the product people typically consume, to determine if the product is a potential health concern and whether it should be recalled.

Working with industry. Microcystins aren’t something you can see, smell, or taste in a product. This is an example of why it is important for companies to have good manufacturing practices, such as testing for potential contaminants, to make sure their products are safe. We work with companies that harvest and use blue-green algae (including AFA) to ensure that they comply with FDA regulations, including manufacturing regulations, and produce safe products. When we determine that contamination has occurred, we work with that company—whether it is a raw material supplier or a product manufacturer—to remove the affected products from the market and implement corrections to prevent future contamination. 

Working with other government agencies. We collaborate with other federal and state agencies to protect the public health. For example, we worked with the Oregon Department of Agriculture and the Oregon Health Authority to respond to microcystins found in products containing AFA harvested from Upper Klamath Lake in Oregon, which led to product recalls in 2018 and 2020. We also routinely exchange information with other federal agencies responsible for addressing issues with harmful algae and cyanobacteria blooms.

Research on microcystins. In 2014-2015, FDA scientists conducted research to evaluate both screening and confirmation methods for detecting microcystins in dietary supplements and AFA raw materials. In 2016, FDA scientists surveyed 51 AFA-containing dietary supplements for microcystins. The survey found that many products contained little to no microcystins while others contained microcystins at or close to the informal standard set by industry.

Product recalls. Two AFA-based dietary supplements (both in 2018) and a beverage containing AFA and other blue-green algae (in 2020) were found to have higher levels of microcystins than the WHO and EPA provisional guidelines, considering the recommended serving size. These investigations led to Class 2 voluntary recalls of the affected products. The products were all linked to several batches of AFA harvested between 2015 and 2017.

Enforcing regulations. Dietary supplements and other foods with unsafe levels of contaminants, such as microcystins, are considered adulterated under the Federal Food, Drug, and Cosmetic Act. To help ensure the safety of dietary supplements and other foods, companies must comply with the applicable Current Good Manufacturing Practices (CGMPs) regulations when they produce dietary supplements, other food products, and their ingredients, including those that contain blue-green algae.

Industry Practices for Harvesting AFA

In 2020-2021, we conducted industry calls with companies that harvest AFA from Upper Klamath Lake in Oregon. During these calls, we discussed testing methods and practices for harvesting and processing to prevent the need for future recalls by manufacturers using AFA in their products.

Based on our conversations with harvesters, we believe that awareness of these practices can prevent future problems. Some examples of the practices used by harvesters to control the presence of microcystins in AFA include:

  1. At the time of harvest, examining AFA at the harvesting site for contaminating cyanobacteria.
  2. At the time of harvest, testing the water and AFA for microcystins.
  3. After harvest, testing the AFA slurry for microcystins.
  4. Before selling AFA products, testing each lot or batch for microcystins.
  5. Using more than one test method to confirm results.
  6. Using a test method that can detect multiple variant forms of microcystins.
  7. Using certified testing laboratories and validated methods.
  8. Providing a certificate of analysis to purchasers for each lot or batch sold.

Information for Consumers

Health risks

If present at significant levels, microcystins can cause liver and kidney damage when consumed. Microcystins have also been shown to cause tumors in laboratory animals. 

Microcystins can affect your health differently depending on how you are exposed (whether through swimming or something you ate), how much you are exposed to, and how often you are exposed. The effects of low-level, long-term exposure to these toxins for any route of exposure is still being determined. For more information on the health effects of exposure to microcystins from the environment (such as from swimming), please see the Microcystin Exposure from Cyanobacterial Harmful Algal Blooms box below.


If you consume products with added AFA or other blue-green algae, here are some steps you can take:

Be an informed consumer. As with all food and drinks you consume, you can stay informed and help others by doing the following:

Learn from the label. If you want to know if a product you consume contains blue-green algae, check the label. Manufacturers of dietary supplements and other food products are required to list ingredients on their product labels. For example, the ingredient section may say “blue-green algae” or “Aphanizomenon flos-aquae” to specify the type. You can learn more on our Food Labeling & Nutrition page.

Follow the directions for use on the label. For dietary supplements, labels include the serving size and the amount of blue-green algae per serving. Don’t take more than this amount. 

Check with your healthcare provider before buying or using a supplement, especially if you are pregnant, nursing, or have a chronic medical condition. Also, check with your pediatrician before giving children dietary supplements. A dietary supplement sold for adults may not be appropriate for children to consume. Also, a recommended serving size for adults may not be a safe amount for children because their bodies are smaller. Most of the blue-green algae products we tested in 2016 were recommended for adult use only, but several labels also contained recommended amounts for children under 12. Checking with your pediatrician first is always a good choice.


Research Publications

  • “Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Quantitation of Microcystins in Blue-Green Algal Dietary Supplements” in J. Agric. Food Chem. 2015, 63, 10303-10312
  • “Improved screening of microcystin genes and toxins in blue-green algal dietary supplements with PCR and a surface plasmon resonance biosensor” in Harmful Algae. 2015, 47, 9–16
  • “Evaluation of Microcystin Contamination in Blue-Green Algal Dietary Supplements in the United States Using a Protein Phosphatase Inhibition Screening Kit” in Heliyon. 2018 Mar 16;4(3):e00573
  • “Microcystin Hepatotoxins at Potentially Hazardous Levels in Algal Dietary Supplements Revealed by a Combination of Bioassay, Immunoassay, and Mass Spectrometric Methods” in J. Agric. Food Chem. 2020, 68, 8016-8025

Microcystin Exposure from Cyanobacterial Harmful Algal Blooms (cyanoHABs)

When cyanobacteria grow out of control, this can result in what is referred to as a cyanobacterial harmful algal bloom (cyanoHAB). Microcystis are one type of cyanobacteria that lead to cyanoHABs. The greatest risks from Microcystis events are usually from exposure to microcystin-contaminated drinking and recreational waters, but they can also make products containing blue-green algae potentially unsafe to consume.

Symptoms of microcystin exposure from cyanoHABs may include:

  • Gastrointestinal issues, such as vomiting, nausea, and diarrhea
  • Abdominal pain
  • Headache
  • Sore throat
  • Dry cough
  • Blistering around the mouth
  • Pneumonia
  • Damage to your liver, kidneys, or reproductive system

We routinely exchange information with other federal agencies responsible for addressing cyanoHAB issues, such as the U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS), and the U.S. Army Corps of Engineers (USACE). To learn more about cyanoHABs and microcystins, here are some additional resources:

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