Spirulina Side Effects and Danger You Should know

Spirulina is a blue-green algae that contains a range of nutrients, such as B-vitamins, beta-carotene, and E-vitamins. It grows in salty freshwater and people use it as a dietary supplement in certain areas of the world for its high protein content. Spirulina is also a healthy source of polyunsaturated fats and C-phycocyanin. In addition, it has antibacterial, antioxidant, anti-inflammatory, immune-boosting, and cholesterol-lowering abilities. Despite having several health benefits, you may wonder if there are side effects of spirulina. (1, 2, 3)

Spirulina Dangers

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Although spirulina is safe for many people, but it may have some side effects and downsides for individuals under certain conditions. Spirulina harvested in the wild contains toxins, which can pose a significant risk. For example, if it grows in the water that is contaminated with heavy metals, bacteria, or damaging particles called microcystins, it may harbor toxins. These toxins can damage the liver when eaten in enormous quantities. In Italy, North America, and China, they have discovered microcystin in algae supplements, which is an increasing problem for public health. Spirulina cultivated in controlled environments is low in microcystins because researchers have established techniques for removing and limiting these toxic compounds during the production. Therefore, make sure you are ingesting spirulina, which is free of microcystins. (4)

Wild-harvested spirulina that grows in contaminated water with heavy metals, bacteria, or damaging particles known as microcystins is toxic to health.

Can Slow Blood Clotting

Spirulina has an anticoagulant effect, which means it can thin your blood and boost blood clotting time. When you are wounded, coagulation helps avoid excessive bleeding or bruising. Spirulina may be hazardous for those taking blood thinners or those with bleeding disorders because it may reduce the capability of your blood to clot, leading to more bleeding. While some studies show spirulina does not influence blood coagulation time. However, there are little knowledge-based studies about its consequences on individuals who are already taking blood-thinning medication. Therefore, if you have a bleeding disorder or are on blood thinners, avoid consuming spirulina to prevent side effects. (5, 6, 7, 8)

Spirulina has an anticoagulant effect, it can thin your blood. Avoid consuming spirulina if you have a bleeding disorder or are taking blood thinners.

Can Worsen Autoimmune Diseases

Spirulina can boost your immune system by reinforcing immune cells called natural killer (NK) cells that attack perceived cell-level threats. Studies on animals and humans show that this effect can help reduce inflammation. However, it can do the opposite and worsen certain autoimmune in people with lupus, various sclerosis, and rheumatoid arthritis in which your immune system attacks your own body cells by enhancing the NK. Although these side effects seem very rare and people with autoimmune condition should avoid spirulina supplements. (9, 10, 11, 12, 13, 15)

People who have lupus, multiple sclerosis, or rheumatoid arthritis should avoid Spirulina supplements. Spirulina may exacerbate certain autoimmune conditions.

Other Downsides

Some individuals may have spirulina allergies. Reactions can be deadly in serious cases. According to one research, individuals with allergies are more likely to respond to spirulina than those without allergies. To prevent side effects, people with allergies should not consume spirulina supplement or should talk to their doctor before using it. Spirulina and other algae contain phenylalanine. Therefore, an individual with phenylketonuria should strictly avoid it. Some minor spirulina side effects may include nausea, sleeplessness, and headaches. However, spirulina is still considered safe, and most individuals experience no side effects. (16, 17, 18)

Some people may be allergic to spirulina. In severe cases, reactions can be fatal.


Spirulina may cause side effects in some people. It is best to consult with a health care provider before taking it. To avoid contaminated spirulina, which contain toxins, only buy product from trusted brands tested by third-party organizations like the U.S. Consumer lab, or NSF International, Pharmacopeia (USP).


  1. Use of the effluent from biogas production for cultivation of Spirulina. Bioprocess Biosyst Eng. 2017.
  2. The fate of microcystins in the environment and challenges for monitoring. Toxins (Basel). 2014.
  3. Detection of the hepatotoxic microcystins in 36 kinds of cyanobacteria Spirulina food products in China. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2008.
  4. Contamination by Microcystis and microcystins of blue-green algae food supplements (BGAS) on the Italian market and possible risk for the exposed population. Food Chem Toxicol. 2012.
  5. Detection of Cyanotoxins in Algae Dietary Supplements. Toxins (Basel). 2017.
  6. Microcystins in water and in microalgae: Do microcystins as microalgae contaminants warrant the current public alarm? Toxicol Rep. 2018.
  7. Enhancement of antitumor natural killer cell activation by orally administered Spirulina extract in mice. Cancer Sci. 2009.
  8. Spirulina elicits the activation of innate immunity and increases resistance against Vibrio alginolyticus in shrimp. Fish Shellfish Immunol. 2016.
  9. Dietary Spirulina platensis enhances humoral and cell-mediated immune functions in chickens. Immunopharmacol Immunotoxicol. 1996.
  10. Antioxidant and anti-inflammatory properties of an aqueous cyanophyta extract derived from Arthrospira platensis: contribution to bioactivities by the non-phycocyanin aqueous fraction. J Med Food. 2015.
  11. Anaphylaxis to Spirulina confirmed by skin prick test with ingredients of Spirulina tablets. Food Chem Toxicol. 2014.
  12. Cyanobacteria: an unrecognized ubiquitous sensitizing allergen? Allergy Asthma Proc. 2011.
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Naeem Durrani BSchttps://defatx.com/
I am a retired pharmacist, nutrition expert, journalist, and more. My interests include medical research, and the scientific evidence around effective wellness practices, which empower people to transform their lives.

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