Are omega-3 supplements safe with blood thinners?
Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
At typical supplement doses of around 1 g, the added bleeding risk appears small, and studies in people on anticoagulants have generally not found significant increases. At 3–4 g and above the effect on bleeding time becomes more meaningful. Tell your doctor either way — do not simply start it.
Key takeaways
- Around 1 g/day appears low-risk; 3–4 g/day is where caution increases.
- Omega-3 lengthens bleeding time by reducing platelet aggregation.
- Surgical teams generally want it stopped roughly a week beforehand.
How the interaction works
EPA and DHA reduce platelet aggregation and lengthen bleeding time — part of why omega-3 was originally thought to be cardioprotective. Added to warfarin, a DOAC, aspirin or clopidogrel, which act on clotting through different routes, the effects can combine. The mechanism is real; the practical size of the risk is dose-dependent.
What the evidence suggests
Studies in patients taking anticoagulants alongside moderate omega-3 doses have generally not found clinically significant bleeding increases, and some cardiology guidance permits it. High-dose prescription omega-3 trials have reported small increases in bleeding events. The reasonable summary: routine supplement doses are probably fine with medical awareness, high doses need a conversation.
Practical steps
Tell whoever manages your anticoagulation before starting. If you are on warfarin, have your INR rechecked a couple of weeks afterwards. Report unusual bruising, nosebleeds, bleeding gums or blood in urine or stool. Stop roughly seven days before planned surgery or dental extraction and tell the team.
Key ingredients to understand
The ingredients most relevant to this question, with what the evidence actually supports:
- Omega-3 Fish Oil (EPA & DHA) — The omega-3 fatty acids EPA and DHA from fish oil have solid evidence for lowering triglycerides and are structurally important for the heart,…
- Krill Oil — Krill oil provides omega-3s (EPA/DHA) in phospholipid form, which may absorb well, plus natural astaxanthin. It's a pricier alternative to…
- Vitamin E — Vitamin E is an essential antioxidant vitamin, but the supplement story is a cautionary one: large trials show it doesn't prevent heart…
- Garlic — Garlic supplements are taken for heart health. The evidence points to modest reductions in blood pressure and cholesterol — real but small —…
Frequently asked questions
Does this apply to DOACs?
Yes. Apixaban, rivaroxaban and similar drugs have no routine monitoring, which is an argument for more caution rather than less.
What about flaxseed or algal oil?
Algal oil supplies the same EPA and DHA and carries the same considerations. Flaxseed provides ALA, converted inefficiently, so the effect is smaller.
Should I stop omega-3 if I start a blood thinner?
Not automatically — ask. There may be a good reason you are taking it.
Related on FactoWiki
- Heart & Cardiovascular Health supplements — the full category
- All health answers
- Ingredient evidence guides
- Omega-3 Fish Oil (EPA & DHA) — ingredient guide
- Krill Oil — ingredient guide
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