Omega-3 (EPA/DHA fish oil) has 3 documented interactions in Magellan’s curated dataset, covering Anticoagulants (blood thinners), Antiplatelet drugs, Blood pressure medications, Orlistat (fat-absorption blocker). Each entry below gives the mechanism as the cited reference states it, the direction the risk runs, how serious that reference treats it, and what to actually do about it — which is, in every case, a conversation with the clinician or pharmacist who manages the prescription rather than a decision you make alone.
What it is. Omega-3 fatty acids are long-chain polyunsaturated fats, principally eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found mainly in oily fish and fish oil; a plant-derived form, alpha-linolenic acid (ALA), occurs in walnuts and flaxseed. Because the body cannot synthesize them, they must be obtained from diet or supplements.
Where it sits on the evidence. Magellan grades the supplement itself as Moderate evidence, with a typical studied dose of Typical studied range 0.5-4 g/day EPA+DHA; triglyceride and blood-pressure effects are dose-dependent, clearest around 2-3 g/day. That grade is about whether it works, not about whether it is safe alongside your medication — the two questions are independent, and this page answers only the second.
Products this covers: Omega-3 EPA/DHA Fish Oil.
How the risks cluster. The entries split across 3 different mechanisms — bleeding risk; additive; absorption and timing — and they are not managed the same way: an absorption problem is fixed by separating the doses in time, an additive or opposing effect is not.
Safety and efficacy are separate questions, and this page only answers the first. For the second, the study Magellan’s coverage of Omega-3 rests on is:
“Omega-3 fatty acids reduced cardiovascular mortality and improved cardiovascular outcomes”
A strong result does not make a supplement safe alongside your prescription, and a documented interaction does not mean the supplement does not work. Magellan grades those two things separately, and neither grade moves for a commission.
Magellan’s Medication Safety Check runs entirely on your device — type the medicines you take and it flags every documented interaction in this dataset. Nothing you type is sent anywhere.
Open the Medication Safety Check →Fish oil has mild antiplatelet activity and can prolong clotting time/raise INR when combined with blood thinners; most studies of 3-6 g/day fish oil do not cause significant bleeding, but periodic INR monitoring is advised for those on warfarin.
Medicines in this group include: Warfarin (Coumadin, Jantoven), Apixaban (Eliquis), Rivaroxaban (Xarelto), Dabigatran (Pradaxa), Edoxaban (Savaysa), Heparin (Lovenox, Enoxaparin), Acenocoumarol (Sintrom), Aspirin (Asa, Bayer aspirin) and 4 more.
Fish oil can itself lower blood pressure slightly, so combining with antihypertensive drugs may increase the blood-pressure-lowering effect.
Medicines in this group include: Amlodipine (Norvasc), Diltiazem (Cardizem, Tiazac), Verapamil (Calan, Verelan), Nifedipine (Procardia, Adalat), Hydrochlorothiazide (Hctz, Microzide), Chlorthalidone (Thalitone), Indapamide (Lozol), Furosemide (Lasix) and 6 more.
Orlistat can reduce absorption of the fatty acids in fish oil; Mayo Clinic recommends taking the supplement and drug about two hours apart.
Medicines in this group include: Orlistat (Xenical, Alli).
These are the warning signs that go with the medication classes on this page. They are general safety-netting, not a prediction that any supplement will cause them.
If something feels seriously wrong, do not wait for an appointment. Call 911 (US) or your local emergency number.
Severity describes the interaction as the cited reference frames it, not how a specific person will react. A “minor” entry in someone with kidney disease, on five other drugs, can matter more than a “major” one in someone on nothing else.
This is a curated set of interactions with citations — not an exhaustive pharmacology database. An interaction that is absent here has not been ruled out; it may simply not be documented in the references Magellan curates from. Supplements are also not batch-tested for identity or contamination the way prescription drugs are, so what is on the label is a claim rather than a guarantee. And most of these entries come from case reports and mechanistic work rather than randomized trials, which is exactly why the sensible response is a pharmacist review rather than either alarm or dismissal.
22 documented interactions across 17 supplements.
15 documented interactions across 14 supplements.
43 documented interactions across 24 supplements.
3 documented interactions · shares a drug class with Omega-3.
8 documented interactions · shares a drug class with Omega-3.
7 documented interactions · shares a drug class with Omega-3.
4 documented interactions · shares a drug class with Omega-3.
The mechanism and the research behind the compound itself.
A–Z of every supplement and drug class in this dataset, plus how to read an interaction.
What the research actually shows, graded independently of affiliate commissions.
Not without checking with the prescriber or pharmacist first. Magellan's dataset grades this as a moderate interaction: Fish oil has mild antiplatelet activity and can prolong clotting time/raise INR when combined with blood thinners; most studies of 3-6 g/day fish oil do not cause significant bleeding, but periodic INR monitoring is advised for those on warfarin. (Source: Omega-3 Fatty Acids - Health Professional Fact Sheet.)
The cited reference specifies an interval: Mayo Clinic recommends taking the supplement and drug about two hours apart. Confirm the exact timing with the pharmacist who dispensed the medication, because it depends on the formulation.
3 interactions are documented in Magellan's curated dataset: 1 moderate, 2 minor. They cover Anticoagulants (blood thinners), Antiplatelet drugs, Blood pressure medications, Orlistat (fat-absorption blocker). Absence from this list is not proof of safety — it means no interaction is documented in the references we curate from.
Magellan lists the typical studied dose as: Typical studied range 0.5-4 g/day EPA+DHA; triglyceride and blood-pressure effects are dose-dependent, clearest around 2-3 g/day. Dose matters for interactions — several of the entries on this page describe effects that only appear at supplemental rather than dietary intakes.