Interaction fact sheet
Omega-3s and anticoagulants
Monitor: a low risk that increases with high doses of EPA.
In a meta-analysis of 11 trials involving more than 120,000 people, omega-3s did not increase bleeding overall. High doses of purified EPA increased relative risk, with a small absolute increase. If you take an anticoagulant, stick to moderate doses and let your doctor know.
In brief
- Mechanism
- Omega-3s slightly reduce platelet aggregation. In theory, this adds to the effect of anticoagulants and antiplatelet drugs.
- Magnitude
- No overall increase in bleeding; with high-dose purified EPA, an absolute increase of about 0.6%.
- Who is affected
- People taking anticoagulants or antiplatelet drugs, especially with omega-3 doses of several grams per day.
- What to do
- Stick to moderate doses and tell your doctor about your omega-3s, especially before surgery.
What large trials show
A meta-analysis published in 2024 pooled 11 randomized trials involving 120,643 patients. Bleeding was no more frequent with omega-3s than with placebo, including brain and gastrointestinal bleeding. In the subgroup receiving high-dose purified EPA, the relative risk of bleeding increased by 50%, but the absolute increase remained around 0.6%.
An analysis of 8 clinical studies involving vulnerable patients, some taking antithrombotic medicines, found no increase in bleeding or changes in clotting tests.
In practice
What you can do
- At dietary intakes and usual supplement doses, around 1 g per day, the risk remains low.
- Above that, if you take an anticoagulant or antiplatelet medicine, ask your doctor for advice.
- Mention your omega-3s before surgery or a tooth extraction.
When to seek advice
- Unusual bleeding, frequent bruising, black stools.
- Wanting to take several grams of omega-3s per day while on medication.
Main sources
- 01Javaid M et al. Bleeding risk in patients receiving omega-3 polyunsaturated fatty acids: a systematic review and meta-analysis of randomized clinical trials. Journal of the American Heart Association, 2024. PubMed
- 02Jeansen S et al. Fish oil LC-PUFAs do not affect blood coagulation parameters and bleeding manifestations. Clinical Nutrition, 2018. PubMed
Frequently Asked Questions (FAQ)
Can you take omega-3s with an anticoagulant?
At usual doses, large trials show no increase in bleeding. Let your doctor know, especially with high doses.
Do omega-3s thin the blood?
They slightly reduce platelet aggregation, but much less than an anticoagulant or aspirin.
Should you stop omega-3s before surgery?
Tell your surgeon or anaesthetist about them; they will decide based on the procedure and your treatment.