Based on NIH | Do fish oil supplements interact with aspirin and increase the risk of bleeding?

Fish oil supplements and aspirin: what we know about bleeding risk

Short answer: Fish oil (omega‑3 fatty acids like EPA and DHA) can modestly affect blood clotting, and package labels and clinical references caution that combining fish oil with antiplatelet drugs (like aspirin) may increase bleeding risk, especially at high doses. ^{[1] [2]} At the same time, clinical studies including those using high-dose fish oil with aspirin (and even with a second antiplatelet such as clopidogrel) generally have not shown a significant increase in clinically important bleeding compared with antiplatelet therapy alone. ^{[3] [4]}

How fish oil and aspirin affect clotting

• Aspirin reduces platelet stickiness to prevent clots, which can increase bleeding (for example, nosebleeds, easy bruising). This effect is intentional in heart protection.
• Fish oil (EPA/DHA) can also reduce platelet activity and may slightly prolong bleeding time, particularly at higher supplemental doses. ^[5] Some trials reported longer bleeding time with omega‑3s, but the prolongation typically stayed within normal limits without leading to major clinical bleeding in studied settings. ^{[5] [6]}

What official and label guidance says

• Consumer and clinical references commonly advise that fish oil taken with anticoagulants or antiplatelet drugs (such as aspirin) might increase bleeding risk, especially at higher doses. ^{[1] [2]}
• FDA‑listed prescribing information for omega‑3‑acid ethyl esters notes bleeding-time prolongation in trials and recommends periodic monitoring when used with drugs affecting coagulation (including antiplatelet agents). ^{[5] [7]}

What clinical studies show

• In a cohort of cardiovascular patients taking high‑dose fish oil (~3 g/day) plus aspirin and clopidogrel, bleeding rates were not higher than in matched patients on aspirin and clopidogrel without fish oil; major bleeding was rare and not increased. ^[3]
• Broader reviews find that while omega‑3s influence platelet function and hemostasis, they have not been associated with increased risk of clinically significant bleeding across monotherapy or combination therapy settings. ^[4]
• In a small randomized crossover study, adding a single aspirin dose did not significantly prolong bleeding times beyond olive oil when participants had been taking high‑dose omega‑3 supplements, suggesting no additive effect on bleeding time in that context. ^[8]

Practical takeaways

• Dose matters: Routine, moderate fish oil doses are generally considered safe for most people, but higher doses may be more likely to prolong bleeding time. ^[2]
• Combination with aspirin: A theoretical and label‑level risk exists, so caution is reasonable, yet available clinical data have not shown a clear increase in major bleeding when fish oil is combined with aspirin (with or without clopidogrel). ^{[3] [4]}
• Individual factors: A personal history of bleeding, use of additional blood thinners (e.g., warfarin, DOACs), upcoming surgery, older age, low body weight, liver disease, or heavy alcohol use may tilt the balance toward avoiding high-dose fish oil or using closer monitoring. ^[5]
• Peri‑procedural considerations: Some clinicians pause nonessential supplements before surgery to simplify bleeding risk, although reviews do not support a routine need to stop omega‑3s purely due to bleeding concerns; decisions should be individualized with your surgeon or cardiologist. ^[4]

Suggested safe-use tips

• Keep fish oil doses moderate unless your clinician prescribes higher amounts for triglycerides.
• If you’re on daily aspirin, start fish oil only after discussing with your clinician, especially if you also take other antiplatelets or anticoagulants. ^[5]
• Watch for warning signs like unusual bruising, black stools, nosebleeds that are hard to stop, or prolonged bleeding from cuts, and report them promptly. ^[2]
• For upcoming procedures, ask your healthcare team whether to pause supplements temporarily. ^[4]

Quick reference table

Question	What evidence suggests
Do omega‑3s affect clotting time?	They can prolong bleeding time slightly, typically within normal limits, and without clear clinical bleeding in trials. [5] [6]
Do official sources warn about interactions with aspirin?	Yes, they caution that omega‑3s combined with antiplatelets/anticoagulants may increase bleeding risk, particularly at higher doses. [1] [2]
Do clinical studies show more major bleeding with fish oil + aspirin?	Studies (including high‑dose fish oil with aspirin ± clopidogrel) have not shown increased clinically significant bleeding compared with antiplatelets alone. [3] [4]
Should everyone stop omega‑3s before procedures?	Broad reviews do not support a routine need to stop, but decisions should be individualized with the surgical/medical team. [4]

Bottom line

• There is a plausible and label‑level risk that fish oil could add to aspirin’s bleeding effect, especially at higher doses. ^{[1] [2]}
• However, clinical data to date generally do not show a meaningful increase in major bleeding when fish oil is combined with aspirin (even with dual antiplatelet therapy), though individualized assessment and prudent monitoring are sensible. ^{[3] [4]}

If you’re considering adding fish oil while on aspirin, it’s wise to review your dose, other medicines, and bleeding history with your healthcare professional, and to monitor for any unusual bleeding symptoms. ^{[5] [2]}