Can you take fish oil supplements if you are on blood thinners? The Essential Guide

October 19, 2025 •

4 min read

According to the Centers for Disease Control and Prevention (CDC), millions of adults in the U.S. take fish oil supplements, often for their potential cardiovascular benefits. However, if you're taking anticoagulant or antiplatelet medications, a critical question arises: Can you take fish oil supplements if you are on blood thinners? The answer involves a careful evaluation of risks, potential interactions, and always consulting with your healthcare provider.

Quick Summary

Taking fish oil supplements while on blood thinners poses a potential risk of increased bleeding. Discuss any supplement regimen with your doctor to assess dosage, manage potential interactions, and monitor for adverse effects.

Key Points

Consult a Doctor First: Never start a fish oil supplement while on blood thinners without first discussing it with your healthcare provider.
Monitor for Bleeding: Be vigilant for signs of increased bleeding or bruising, and report any unusual symptoms to your doctor immediately.
Higher Intake Risk: The risk of bleeding increases significantly with higher intakes of fish oil.
Discuss All Supplements: Inform your doctor about all dietary supplements and herbal remedies, as many can interact with anticoagulant medications.
Consider Food Sources: Eating oily fish like salmon is a potentially safer way to get omega-3s than high-intake supplements, as the concentration is lower and poses less risk of interaction.
Monitor INR Levels (for Warfarin users): If you take warfarin, your doctor will need to monitor your blood's clotting time more frequently when adding a fish oil supplement.

The Interaction Between Fish Oil and Blood Thinners

Fish oil is known for its high concentration of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These compounds have a mild anti-clotting effect by inhibiting platelet aggregation, a crucial step in the blood clotting process. Separately, this anti-platelet effect is often considered beneficial for heart health. However, when combined with prescribed blood-thinning medications like anticoagulants (e.g., warfarin) and antiplatelets (e.g., aspirin), this effect becomes a critical concern.

The Mechanism of Action and Risk of Bleeding

Blood thinners work by different mechanisms to prevent blood clots. Warfarin, for example, interferes with vitamin K-dependent clotting factors. The new oral anticoagulants (NOACs) or direct oral anticoagulants (DOACs), such as rivaroxaban (Xarelto) and apixaban (Eliquis), work by directly inhibiting specific clotting factors. Fish oil can add to this effect, potentially increasing the risk of bleeding. While the anti-clotting effect of fish oil supplements is considered mild, its combination with potent prescription drugs can lead to an additive or even synergistic effect, requiring close medical supervision.

Clinical Evidence and Guidelines

The research on this interaction has yielded mixed results, leading to cautious medical advice. Some older studies raised concerns about the combination, while more recent reviews suggest that the bleeding risk with typical intakes is low. For instance, a 2015 review in Australian Family Physician concluded that certain intakes appeared safe with warfarin and aspirin, though data with newer anticoagulants were lacking at the time. However, a case report highlighted the increased risk, particularly in elderly patients taking fish oil alongside other blood thinners. Most experts agree that the risk is related to the amount consumed, and the possibility of interaction, no matter how small, necessitates a conversation with a healthcare professional.

Important Considerations for Supplement Users

Before Starting Fish Oil

Consult Your Doctor: Before you start taking any new supplement, including fish oil, inform your doctor about all prescription and over-the-counter medications you are taking.
Disclose All Supplements: This includes herbal remedies, as some (like ginseng and ginkgo biloba) can also interact with blood thinners.
Blood Monitoring: For those on warfarin, regular blood monitoring (INR tests) is crucial. Your doctor will likely need to monitor this more frequently to ensure your blood's clotting time remains in the safe therapeutic range.

While Taking Fish Oil and Blood Thinners

Watch for Bleeding Signs: Be vigilant for any unusual signs of bleeding, such as frequent bruising, nosebleeds, blood in urine or stool, or bleeding gums.
Report Changes to Your Doctor: If you experience any of these symptoms, contact your doctor immediately. Do not attempt to adjust your medication or supplement regimen yourself.
Follow Medical Advice: The risk of bleeding can increase with higher intakes of fish oil. Adhere to your doctor's recommendations and never exceed them without their approval.

Comparison: Fish Oil Supplements vs. Oily Fish


Feature	Fish Oil Supplements	Oily Fish (e.g., Salmon, Sardines)
Omega-3 Concentration	Can provide concentrated amounts of EPA and DHA.	Lower, naturally occurring amounts of EPA and DHA.
Bleeding Risk	Potential for increased bleeding risk, especially with higher intake or when combined with blood thinners.	Minimal to no increased bleeding risk, even with regular consumption, due to lower overall omega-3 intake.
Doctor Consultation	Required before starting, especially when on blood thinners.	Generally not necessary for moderate, regular consumption.
Dietary Stability	Can be considered a dietary change that impacts medication effectiveness and should be discussed with a doctor.	Considered part of a balanced diet and typically does not require a medication-level stability consideration.
Contaminant Concerns	Generally purified and tested for contaminants like mercury.	May contain trace amounts of mercury or other contaminants depending on the fish.

The Verdict: Proceed with Caution

While fish oil offers recognized benefits for cardiovascular health, the interaction with blood-thinning medication is a serious consideration that demands a cautious and informed approach. The crucial takeaway is that self-prescribing is not an option. Your healthcare provider is the only person who can properly assess the risks and benefits for your specific medical situation. They can help determine if a controlled intake of fish oil is appropriate for you and monitor you closely for any adverse effects.

For those seeking omega-3s without the supplemental risk, consuming oily fish is an excellent alternative. Fatty fish like salmon and sardines provide these beneficial fatty acids in a natural, less concentrated form, which poses a far lower risk of interaction with your medication. Additionally, your doctor may suggest other dietary sources of omega-3s, such as flaxseed or algae oil, depending on your dietary needs. The decision to combine fish oil supplements with blood thinners must be made in close partnership with your medical team to ensure your safety and the effectiveness of your treatment.

For more information on supplements and their interactions, the National Center for Complementary and Integrative Health (NCCIH) offers a valuable resource on omega-3s and heart health.

Conclusion: Prioritize Medical Advice

Ultimately, the question of whether can you take fish oil supplements if you are on blood thinners should only be answered by a medical professional. While many studies suggest that lower intakes of fish oil may not significantly increase bleeding risk, the potential for interaction with blood-thinning medications is real and can be dangerous. Never begin a new supplement without full disclosure to your doctor, who can guide you on the safest course of action, whether that involves a controlled supplement intake, changes in your diet, or alternative sources of omega-3 fatty acids. Your health and safety are the top priorities, and responsible supplementation is key to maintaining both.

Frequently Asked Questions

Yes, but only under the strict supervision of a healthcare provider. Some studies suggest lower intakes are relatively safe, but it's crucial for your doctor to assess your specific risk and monitor your condition. They may want to check your blood's clotting time more frequently if you are on warfarin.

You should watch for signs of increased bleeding or bruising. These can include frequent and easy bruising, prolonged bleeding from minor cuts, bleeding gums, nosebleeds, red or dark stools, or blood in your urine.

The potential for interaction exists with all blood thinners, including older anticoagulants like warfarin and newer DOACs. Since the anti-clotting effects are additive, it's safest to assume an interaction is possible regardless of the specific medication.

Yes, eating fatty fish is a potentially safer way to obtain omega-3 fatty acids. The concentration of omega-3s in fish is naturally lower than in supplements, and regular consumption is generally not associated with an increased bleeding risk for those on blood thinners.

Yes, many other supplements can interact with blood thinners. Examples include herbal remedies like ginseng, ginkgo biloba, and high-intake vitamin E. It is essential to disclose all supplements to your doctor.

There is no universally safe intake; it depends on individual factors and the specific medication. Some research suggests that lower intakes are likely safe, but this must be determined and monitored by your doctor.

Alternatives include dietary sources like flaxseeds, chia seeds, and walnuts, which contain alpha-linolenic acid (ALA). Algae oil is another option that provides pre-formed EPA and DHA, similar to fish oil, and is also suitable for vegans.