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SupplementScience

Chlorella Side Effects & Safety

Reviewed by·PharmD, BCPS

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • GI discomfort (gas, bloating, diarrhea) — most common, especially in the first week; starting with a low dose and increasing gradually minimizes this
  • Green discoloration of stool (harmless — due to high chlorophyll content)
  • Sun sensitivity — high chlorophyll content may theoretically increase photosensitivity in some individuals
  • Allergic reactions — rare but possible, especially in individuals with algae or mold sensitivities
  • Nausea — typically transient and dose-dependent; resolves with dose reduction

Drug & Supplement Interactions

  • Warfarin and anticoagulants — chlorella contains vitamin K which may reduce anticoagulant effectiveness; monitor INR closely
  • Immunosuppressants (cyclosporine, tacrolimus) — chlorella stimulates NK cell activity and may counteract immunosuppressive therapy
  • Iron supplements — chlorella contains significant iron; consider total iron intake to avoid excess
  • Blood pressure medications — chlorella may have mild antihypertensive effects; additive blood pressure lowering possible
  • Thyroid medications — chlorella contains iodine; may affect thyroid medication dosing

Maximum Dose

Do not exceed: 10g/day (doses up to 10g have been used in clinical studies without significant adverse effects)

Full Chlorella Guide

References

  1. Kwak JH, Baek SH, Woo Y, Han JK, Kim BG, Kim OY, Shin JH (2012). Beneficial immunostimulatory effect of short-term Chlorella supplementation: enhancement of natural killer cell activity and early inflammatory response. Nutrition Journal. DOI PubMed
  2. Ryu NH, Lim Y, Park JE, Kim J, Kim JY, Kwon SW, Kwon O (2014). Impact of daily Chlorella consumption on serum lipid and carotenoid profiles in mildly hypercholesterolemic adults. Nutrition Journal. DOI PubMed
  3. Uchikawa T, Kumamoto Y, Maruyama I, Kumamoto S, Ando Y, Yasutake A (2010). Enhanced elimination of tissue methylmercury in Parachlorella beijerinckii-fed mice. Journal of Toxicological Sciences. PubMed
  4. Azocar J, Diaz A (2013). Efficacy and safety of Chlorella supplementation in adults with chronic hepatitis C virus infection. World Journal of Gastroenterology. DOI PubMed
  5. Merchant RE, Andre CA (2001). A review of recent clinical trials of the nutritional supplement Chlorella pyrenoidosa in the treatment of fibromyalgia, hypertension, and ulcerative colitis. Alternative Therapies in Health and Medicine. PubMed
  6. Panahi Y, Darvishi B, Jowzi N, Beiraghdar F, Sahebkar A (2016). Chlorella vulgaris: a multifunctional dietary supplement with diverse medicinal properties. Current Pharmaceutical Design. DOI PubMed
  7. Otsuki T, Shimizu K, Iemitsu M, Kono I (2011). Salivary secretory immunoglobulin A secretion increases after 4-weeks ingestion of chlorella-derived multicomponent supplement in humans. Nutrition Journal. DOI PubMed