Skip to main content
Supplement ScienceSupplementScience

Chlorella Side Effects & Safety

Evidence:Emerging
·

This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — 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)

Looking for a well-tested Chlorella?
All our top picks are third-party verified for purity
Full Chlorella Guide

References

  1. RCTKwak 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. RCTRyu 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. RCTAzocar J, Diaz A (2013). Efficacy and safety of Chlorella supplementation in adults with chronic hepatitis C virus infection. World Journal of Gastroenterology. DOI PubMed
  4. 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
  5. 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
  6. 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
  7. Pinto-Leite M, Martins D, Ferreira AC, Silva C, et al. (2025). The Role of Chlorella and Spirulina as Adjuvants of Cardiovascular Risk Factor Control: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.. Nutrients. DOI PubMed
Show 4 more references
  1. Meta-analysisSherafati N, Bideshki MV, Behzadi M, Mobarak S, et al. (2022). Effect of supplementation with Chlorella vulgaris on lipid profile in adults: A systematic review and dose-response meta-analysis of randomized controlled trials.. Complementary therapies in medicine. DOI PubMed
  2. Meta-analysisFallah AA, Sarmast E, Habibian Dehkordi S, Engardeh J, et al. (2018). Effect of Chlorella supplementation on cardiovascular risk factors: A meta-analysis of randomized controlled trials.. Clinical nutrition (Edinburgh, Scotland). DOI PubMed
  3. Jafari A, Mardani H, Nezhad BP, Hekmatdoost A (2026). The beneficial effects of Chlorella vulgaris supplementation on health-related indices in patients with non-alcoholic fatty liver disease: a GRADE-assessed systematic review and meta-analysis.. BMC cardiovascular disorders. DOI PubMed
  4. Lacurezeanu A, Vodnar DC (2025). Arthrospira platensis and Chlorella vulgaris Consumption on Iron Status: A Systematic Review of In Vivo Studies.. Molecular nutrition & food research. DOI PubMed