Skip to main content
Supplement ScienceSupplementScience

Flaxseed Oil Side Effects & Safety

Evidence:Moderate
·

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

  • Mild GI discomfort (bloating, loose stools) — most common at higher doses; usually resolves within a few days
  • Allergic reactions — rare but possible in individuals with flaxseed or linseed allergy
  • Increased bleeding tendency at very high doses — due to omega-3 antiplatelet effects
  • Estrogenic effects from lignans — theoretical concern in hormone-sensitive conditions, though clinical evidence suggests protective rather than stimulatory effects
  • Rapid oxidation if improperly stored — rancid flaxseed oil may cause nausea and has reduced nutritional value

Drug & Supplement Interactions

  • Anticoagulants and antiplatelets (warfarin, aspirin, clopidogrel) — ALA omega-3s have mild antiplatelet activity; may increase bleeding risk at high doses
  • Blood pressure medications — flaxseed oil may modestly lower blood pressure; monitor for additive hypotension
  • Blood sugar-lowering medications — some evidence flaxseed may affect glycemic control; monitor blood glucose
  • Hormone therapies and oral contraceptives — lignans have weak phytoestrogenic activity; theoretical interaction with estrogen-modulating drugs

Maximum Dose

Do not exceed: 4 tablespoons/day (60 mL); higher doses offer minimal additional benefit and may cause GI discomfort

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

References

  1. Meta-analysisPan A, Yu D, Demark-Wahnefried W, Franco OH, Lin X (2009). Meta-analysis of the effects of flaxseed interventions on blood lipids. The American Journal of Clinical Nutrition. DOI PubMed
  2. Meta-analysisKhalesi S, Irwin C, Schubert M (2015). Flaxseed consumption may reduce blood pressure: a systematic review and meta-analysis of controlled trials. The Journal of Nutrition. DOI PubMed
  3. RCTNeukam K, De Spirt S, Stahl W, Bejot M, Maurette JM, Tronnier H, Heinrich U (2011). Supplementation of flaxseed oil diminishes skin sensitivity and improves skin barrier function and condition. Skin Pharmacology and Physiology. DOI PubMed
  4. RCTZhao G, Etherton TD, Martin KR, West SG, Gillies PJ, Kris-Etherton PM (2004). Dietary alpha-linolenic acid reduces inflammatory and lipid cardiovascular risk factors in hypercholesterolemic men and women. The Journal of Nutrition. DOI PubMed
  5. McNabb TB, Young I, Newman RG, Skinner RC, et al. (2024). Supplementation of Olive Oil and Flaxseed Oil on Blood Pressure and Inflammation in Healthy and At-Risk Adults: A Systematic Literature Review and Meta-Analysis.. Current hypertension reviews. DOI PubMed
  6. Meta-analysisTabrizi R, Azizi Z, Bazmi S, Keshavarzian O, et al. (2024). The impact of flaxseed oil on lipid profiles, weight loss, and inflammatory markers in hemodialysis patients: A systematic review and meta-analysis of randomized controlled trials.. Therapeutic apheresis and dialysis : official peer-reviewed journal of the International Society for Apheresis, the Japanese Society for Apheresis, the Japanese Society for Dialysis Therapy. DOI PubMed
  7. Mahmudiono T, Jasim SA, Karim YS, Bokov DO, et al. (2022). The effect of flaxseed oil consumtion on blood pressure among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized clinical trials.. Phytotherapy research : PTR. DOI PubMed
Show 3 more references
  1. Tamtaji OR, Milajerdi A, Reiner Ž, Dadgostar E, et al. (2020). Effects of flaxseed oil supplementation on biomarkers of inflammation and oxidative stress in patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials.. Clinical nutrition ESPEN. DOI PubMed
  2. La Banudi B, Leksono P, Anasiru MA (2024). Effect of Fish-Based Diet on Malnourished Children: A Systematic Review.. Iranian journal of medical sciences. DOI PubMed
  3. Musazadeh V, Abolghasemian M, Kavyani Z, Moridpour AH, et al. (2024). The effects of flaxseed (Linum usitatissimum) supplementation on anthropometric indices: An updated systematic review and meta-analysis of randomized clinical trials.. Complementary therapies in medicine. DOI PubMed