Based on NIH | Can losartan be taken on an empty stomach, and is there any interaction with eating fish or taking fish oil supplements?

Quick answer

Yes losartan can be taken on an empty stomach or with food. ^{[1] [2]} Eating fish or taking fish oil supplements generally does not cause a harmful interaction with losartan; fish oil may modestly lower blood pressure, so you might notice a small additive effect with your medication. ^{[3] [4]} That said, losartan does have important interactions with potassium supplements, potassium-containing salt substitutes, and certain pain medications (NSAIDs). ^{[5] [6]}

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How to take losartan

• With or without food: Losartan tablets are designed to be taken with or without meals, so you can choose the schedule that fits your routine. ^{[1] [2]}
• Food’s effect on absorption: A meal can slow how quickly losartan is absorbed and reduce the peak blood level, but overall exposure (AUC) changes only slightly, which is why standard guidance allows dosing regardless of meals. ^{[7] [8]} In combination products or co‑administration with certain other drugs, food can reduce the peak of losartan and its active metabolite; however, this effect is typically not clinically significant for most people. ^[9]

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Fish and fish oil: interactions and considerations

• No direct harmful interaction: Omega‑3 fatty acids from fish or fish oil are generally safe with common prescription drugs, including antihypertensives, and are not known to cause adverse interactions with losartan. ^{[3] [10]}
• Possible additive blood pressure effect: Fish oil can slightly lower blood pressure, especially at higher doses (≥3 g/day of EPA+DHA), so when combined with losartan, you may see a modest additive effect. ^{[4] [3]}
• Bleeding risk context: Fish oil has mild antiplatelet properties; even up to 4 g/day, clinical studies have not shown increased major bleeding when used with anticoagulant or antiplatelet drugs, but caution is sensible if you are on blood thinners. ^[3] If you take aspirin or other blood thinners, discuss fish oil dose with your clinician. ^[3]
• Dietary guidance: Many heart-health guidelines support eating oily fish regularly (about two servings per week), or using ~1 g/day fish oil for cardiovascular support, with higher doses (2–4 g/day) reserved for lowering triglycerides. ^{[10] [3]}

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Important losartan interactions to keep in mind

• Potassium and salt substitutes: Avoid or use caution with potassium supplements and potassium-containing salt substitutes because losartan can increase potassium levels. ^{[5] [6]}
• NSAIDs (pain relievers like ibuprofen/naproxen): These may reduce kidney function and blunt blood pressure control when combined with losartan, especially in people who are older, dehydrated, or have kidney disease. ^{[5] [6]}
• Diuretics (“water pills”): Can be used with losartan but may increase the risk of low blood pressure or changes in electrolytes; monitoring is often needed. ^{[6] [11]}

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Practical tips

• Consistency helps: Take losartan at the same time each day, with or without food, based on what you can stick with long-term. ^{[1] [2]}
• Monitor blood pressure: If you start fish oil (especially at higher doses) or significantly increase fish intake, keep an eye on your blood pressure, as you might need a dose adjustment over time. ^{[4] [3]}
• Watch potassium: Be cautious with high-potassium diets and supplements; ask about safe choices for salt substitutes. ^{[5] [6]}
• Check your full medication list: If you regularly use NSAIDs for pain, discuss alternatives and monitoring with your clinician. ^{[5] [6]}

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Key takeaways

• Losartan can be taken on an empty stomach or with food. ^{[1] [2]}
• Fish and fish oil do not have a harmful interaction with losartan; fish oil may slightly lower blood pressure and could add to losartan’s effect. ^{[3] [4]}
• Avoid or be careful with potassium products and NSAIDs while on losartan. ^{[5] [6]}