Based on FDA | Does taking fish oil supplements interact with Warfarin and increase the risk of bleeding?

Fish oil supplements can modestly affect bleeding, but a clear and consistent increase in major bleeding with warfarin has not been demonstrated; careful monitoring is advised if you use both together. ^{[1] [2]}

What we know about the interaction

• Fish oil (omega‑3 fatty acids like EPA/DHA) can reduce platelet activity and may prolong bleeding time, which is the time it takes for a small cut to stop bleeding. This effect has been observed in some trials, though the prolongation generally stays within normal limits and has not consistently led to clinically significant bleeding. ^{[2] [3]}
• Because warfarin also reduces blood clotting by a different mechanism, there is a theoretical additive effect when combined with fish oil. Product labeling for prescription omega‑3 fish oil notes that omega‑3s may prolong bleeding time and recommends periodic monitoring when used with anticoagulants or antiplatelet medicines. ^{[2] [3]}
• Consumer-facing medical guidance similarly notes the possibility that fish oil taken with anticoagulants or antiplatelet agents might increase bleeding risk. ^[1]

Evidence from clinical studies

• Randomized data in people taking blood thinners are limited but reassuring. In a large postoperative cohort where participants received fish oil 4 g/day plus either aspirin or warfarin (target INR 2.5–4.2), researchers did not find an excess of bleeding episodes attributable to fish oil, and bleeding time was not increased by supplementation. ^[4]
• In healthy volunteers, fish oil can slightly prolong bleeding time, but even when combined with a single dose of aspirin the change did not appear clinically meaningful in controlled testing. ^[5]
• In older adults given common supplemental doses of omega‑3s, a systematic review of randomized trials did not identify severe bleeding events, with adverse effects mostly limited to gastrointestinal symptoms. These trials were not specifically designed around warfarin users, but they add context that serious bleeding was uncommon at typical doses studied. ^[6]

Practical guidance if you take warfarin

• Discuss any plan to start or stop fish‑oil supplements with your clinician or anticoagulation clinic, and let them know the exact product and dose. Warfarin dosing is individualized, and adding or removing supplements can affect monitoring plans. ^[2]
• If you and your clinician decide to continue fish oil with warfarin, periodic monitoring for signs of bleeding (easy bruising, nosebleeds, gum bleeding, black or tarry stools) and routine INR checks are advisable, especially after a dose change or brand switch. ^{[2] [3]}
• Keep your omega‑3 intake consistent from week to week. Large swings in dose or switching between high‑EPA/DHA products may change antiplatelet effects and could, in theory, alter bleeding tendency. ^[2]
• Be cautious with “stacking” other agents that affect clotting (e.g., aspirin, clopidogrel, NSAIDs like ibuprofen, and herbal products such as ginkgo or garlic) because combined effects can raise bleeding risk. ^[1]
• For many people on warfarin, modest doses of fish oil (for example, 1–2 g/day of combined EPA+DHA) appear unlikely to cause major bleeding when monitored, but higher doses (≥4 g/day) should be approached more cautiously and with closer follow‑up. ^{[4] [6]}

Bottom line

• There is a plausible interaction because omega‑3s can modestly inhibit platelet function and prolong bleeding time, and labeling advises monitoring when combined with anticoagulants. ^{[2] [3]}
• However, available clinical data including studies in individuals on warfarin suggest that fish oil does not clearly increase clinically significant bleeding when used at common doses and with appropriate monitoring. ^{[4] [6]}
• The safest approach is to coordinate with your clinician, keep dosing consistent, and monitor for bleeding symptoms and INR changes when combining fish oil with warfarin. ^{[2] [3] [1]}

---

Quick comparison

Topic	Fish oil alone	Fish oil + warfarin
Effect on bleeding time	May prolong slightly; usually within normal range and not clinically significant. [2]	Additive theoretical effect; monitoring recommended by product labeling. [2]
Evidence for major bleeding	No consistent increase in severe bleeding in RCTs at common doses. [6]	Study with 4 g/day fish oil in patients on aspirin or warfarin showed no excess bleeding episodes. [4]
Recommended action	Use within typical doses and monitor if you have bleeding risks. [2]	Inform clinician, maintain consistent dosing, and monitor INR and bleeding signs. [2] [3]

If you notice unusual bruising, nosebleeds, or black stools while taking both, contact your clinician promptly. ^[2]