Spirulina Side Effects

Spirulina is a nutrient-rich blue-green algae sometimes used to improve nutrition or as a form of alternative medicine, although there isn't enough scientific evidence to recommend it for treating any health condition, according to the University of Maryland Medical Center. It may not be safe for everyone, so check with your doctor before adding it to your daily routine.

Side Effects

If you take spirulina, it could cause certain side effects, including nausea, stomach pain, vomiting, thirst, weakness, rapid heartbeat, liver damage or shock. This supplement is generally considered safe even when taken in high amounts, however. The side effects are most likely if your spirulina is contaminated, so be sure to purchase this product from a reputable source that has tested it for contaminants.

Potential Medication Interactions

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Although no medication interactions are well-documented, spirulina may interact with medications that suppress your immune system and with blood thinners. If you are on these medications, you'll want to either avoid spirulina entirely or take it under the supervision of your doctor.

Risk of Contamination

Purchase spirulina grown in a laboratory, which includes most types of spirulina sold in the United States, instead of spirulina harvested from outdoor sources. When spirulina is grown in waters contaminated with heavy metals, including lead or mercury, it will become contaminated with these metals. Spirulina can also be contaminated with substances called anatoxin and microcystin, which can be toxic. For this reason, some researchers recommend limiting spirulina consumption to no more than 50 grams per day.

Precautions and Contraindications

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Because of the risk for contamination, spirulina isn't recommended for women who are pregnant or nursing. People with phenylketonuria shouldn't take this supplement because it provides all of the amino acids, including phenylalanine, which is dangerous for people with this condition. Those with autoimmune diseases should also avoid spirulina supplements, as they may stimulate the immune system and increase your symptoms.