Do Fish Oil Supplements Interact with Losartan?

Fish oil (omega-3 fatty acids like EPA/DHA) does not have a direct, well-documented drug–drug interaction with losartan (an angiotensin II receptor blocker), but it can modestly lower blood pressure on its own. Because losartan also lowers blood pressure, using fish oil alongside it could add to the blood pressure–lowering effect and, in some people, contribute to lightheadedness or low readings. ^{[1] [2]} This is generally a mild, predictable pharmacodynamic overlap rather than a harmful interaction, and most adults tolerate the combination well when doses are typical. ^{[3] [4]}

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What the Evidence Suggests

• Blood pressure effects: Multiple clinical studies show omega-3 supplements can produce small reductions in blood pressure, especially at higher daily doses (around 3–4 g of EPA/DHA). ^[5] This decrease is typically modest (often a few mmHg) but can be more noticeable in older adults or those with hypertension. ^[6] Adding fish oil to existing antihypertensive therapy has been associated with additional small reductions in blood pressure in treated hypertensives. ^[7]

• Losartan specifics: Authoritative drug interaction listings for losartan do not flag fish oil as a specific interaction of concern. The main practical consideration is the additive lowering of blood pressure when combined with supplements that also reduce blood pressure. ^{[8] [9]}

• Bleeding considerations: Omega-3s can prolong bleeding time at higher doses, and product labels for prescription-strength omega-3s acknowledge this effect; however, clinical trials have generally not shown clinically significant bleeding episodes from omega-3s alone. Bleeding risk is primarily a concern when fish oil is taken with anticoagulants or antiplatelet drugs (like warfarin or clopidogrel), not with losartan. ^{[10] [11]} High doses may increase bleeding risk, so caution is advised if you use blood-thinners. ^{[12] [13]}

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Practical Guidance

• Typical supplement doses: Many over-the-counter fish oil products provide 1,000 mg of fish oil per capsule but only around 300–600 mg of combined EPA/DHA per capsule; doses in the 1–2 g/day EPA/DHA range are common for general wellness. At these doses, blood pressure effects are usually small, and most people on losartan will not experience problems beyond potentially slightly lower readings. ^{[5] [6]}

• Monitor blood pressure: If you start or increase fish oil while on losartan, check your blood pressure at home for 1–2 weeks to see how you respond. Watch for symptoms of low blood pressure such as dizziness, faintness, or unusual fatigue, and discuss any changes with your clinician. ^{[1] [2]}

• Bleeding watch-outs: If you also take aspirin, clopidogrel, warfarin, or other agents that affect clotting, talk to your clinician before adding or increasing fish oil, and report easy bruising, nosebleeds, or prolonged bleeding. This caution is about clotting medicines not losartan itself. ^{[13] [12]}

• Quality and dosing: Choose products that list the exact amounts of EPA and DHA per serving. Prescription omega-3 formulations used for high triglycerides have clearer dosing and quality standards and also note the potential for prolonged bleeding time, though clinically significant events are uncommon. ^{[10] [11]}

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Side Effects to Expect

• Common, mild effects: Fishy aftertaste, burping, heartburn, nausea, loose stools, and occasional rash can occur, often improved by taking capsules with meals or using enteric-coated products. ^{[14] [12]}

• High-dose risks: Very high intakes can increase bleeding tendency and, in some analyses, have been linked to a possible increase in stroke risk, though this remains debated and more relevant at doses above typical supplement ranges. Use high doses only under medical guidance. ^{[14] [12]}

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Bottom Line

• No direct harmful interaction with losartan is established, but fish oil can slightly lower blood pressure, which may add to losartan’s effect. Monitor your readings and symptoms when combining them, especially if you increase your fish oil dose. ^{[1] [2]}
• Bleeding concerns relate mainly to combining fish oil with blood-thinning drugs, not with losartan alone. If you use anticoagulants or antiplatelets, consult your clinician before adding fish oil. ^{[13] [10]}

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Quick Comparison Table

Aspect	Fish Oil (EPA/DHA)	Losartan
Primary effect	Modest BP lowering; triglyceride reduction	BP lowering via angiotensin II blockade
Interaction type	Additive BP-lowering potential	Not known to interact directly with fish oil
Bleeding	May prolong bleeding time at higher doses; caution with anticoagulants/antiplatelets	Not associated with increased bleeding risk
Common side effects	Fishy taste, GI upset	Dizziness, cough (less common than ACE inhibitors), hyperkalemia (rare)

Evidence notes: Fish oil modestly lowers blood pressure; additive effect with BP drugs is possible. ^{[1] [4]} Bleeding time may be prolonged with omega-3s but clinically significant bleeding is uncommon; caution mainly with anticoagulants. ^{[10] [12]} Losartan interaction listings do not highlight fish oil as a specific concern. ^{[8] [9]}