From the Guidelines
Fish oil supplements are contraindicated in individuals with fish or shellfish allergies, and those taking blood-thinning medications, such as warfarin, clopidogrel, or high-dose aspirin, should exercise caution due to the increased risk of bleeding 1. When considering the use of fish oil supplements, it is essential to weigh the potential benefits against the risks. The most recent and highest quality study, published in 2021, highlights the importance of evaluating the potential net benefit of prescription omega-3 fatty acids in patients at high risk of atrial fibrillation (AF) 1. Key points to consider include:
- Fish oil supplements may increase the risk of AF, particularly in patients with established cardiovascular disease or those taking certain medications 1.
- Patients with implanted defibrillators should avoid fish oil due to the potential increased risk of irregular heartbeats 1.
- Individuals with uncontrolled hyperlipidemia should use caution when taking fish oil, as high doses may increase LDL cholesterol levels 1.
- Fish oil may interact with certain medications, including antihypertensives and oral contraceptives, potentially affecting their efficacy 1.
- Pregnant women should exercise caution when taking fish oil supplements due to the potential risk of contaminants, such as mercury, dioxins, and polychlorinated biphenyls (PCBs) 1. Some specific scenarios where fish oil supplements may be contraindicated or require caution include:
- Before surgery, typically discontinued 1-2 weeks prior, due to increased bleeding risk 1.
- In patients with bleeding disorders, who should exercise caution due to the potential increased risk of bleeding 1.
- In individuals with seafood allergies, who should look for highly purified fish oil products or consider algae-based omega-3 supplements instead 1.
From the Research
Contraindications for Fish Oil
- Fish oil may be contraindicated in patients with a known allergy to fish, as it can cause allergic reactions ranging from mild to life-threatening anaphylaxis 2.
- Patients taking anticoagulant medications, such as warfarin, should use fish oil with caution, as it may increase the risk of bleeding due to its antiplatelet effects 3, 4.
- Fish oil may interact with other medications, such as aspirin and clopidogrel, although one study found that high-dose fish oil did not increase the risk of bleeding in patients taking these medications 5.
- However, another study reported a case of elevated international normalized ratio (INR) in a patient taking fish oil and warfarin, suggesting that fish oil can provide additive anticoagulant effects when given with warfarin 4.
- Patients with seafood allergy or intolerance should also exercise caution when taking fish oil supplements, as they may contain allergens or trigger adverse reactions similar to true seafood allergy 6, 2.