Fish Oil (Omega-3)

• Triglyceride lowering: Strong evidence. Prescription-strength EPA/DHA (2–4 g/day) consistently reduces fasting triglycerides by ~20–30% or more in hypertriglyceridemia (AHA science advisory; multiple RCTs).
• Cardiovascular outcomes: Mixed evidence overall. Research suggests EPA-only prescription (icosapent ethyl, 4 g/day) added to statins in high-risk patients with elevated triglycerides reduces major adverse cardiovascular events (strong evidence from a large RCT). Standard mixed EPA/DHA fish oil has not consistently reduced events in broad populations (systematic review/meta-analyses; neutral findings in a large RCT).
• Blood pressure: Moderate evidence for small reductions (about 2–5 mmHg) at intakes around 2–3 g/day EPA+DHA in hypertensive or mixed populations (meta-analysis of RCTs).
• Inflammation/joint health: Moderate evidence that higher-dose marine omega-3s (generally ≥2–3 g/day EPA+DHA for ≥3 months) can modestly reduce pain, morning stiffness, and NSAID use in rheumatoid arthritis (systematic review of RCTs).

Common (often dose-related): fishy aftertaste or breath, dyspepsia/heartburn, nausea, loose stools or diarrhea, abdominal discomfort.
Metabolic/lipids: modest LDL-C increase (typically a few percent) is more likely with DHA-containing products; EPA-only products generally do not raise LDL-C.
Bleeding-related: easy bruising or epistaxis may occur, especially with concurrent anticoagulants/antiplatelets; clinically significant bleeding appears uncommon at standard supplemental doses but risk increases with higher doses and combinations.
Cardiac rhythm: high-dose omega-3 (especially ≥4 g/day) has been associated with an increased incidence of atrial fibrillation in some large RCTs.
Allergy: rare hypersensitivity reactions; greater caution in individuals with fish/shellfish allergy.
Other: reflux/GERD exacerbation, rash (uncommon).

Commonly used ranges in studies (not medical advice):

• General cardiovascular support: 250–1,000 mg/day combined EPA+DHA in cohort studies and some trials.
• Hypertriglyceridemia: 2–4 g/day EPA+DHA (or 4 g/day EPA-only icosapent ethyl) in clinical trials and prescription use under medical supervision, typically reducing triglycerides by ~20–30% or more.
• Blood pressure effects: ~2–3 g/day EPA+DHA associated with small reductions in systolic and diastolic BP in meta-analyses.
• Rheumatoid arthritis symptom relief: ~2.7–3.5 g/day EPA+DHA for ≥3 months in RCTs.
  Notes: Formulation (ethyl ester vs triglyceride) and taking with meals influence absorption; optimal dosing varies by individual, indication, and product purity.

• Known allergy to fish or fish oil components (consider algae-derived DHA/EPA alternatives if appropriate).
• Active bleeding, bleeding disorders, or history of hemorrhagic stroke (avoid or use only with medical supervision).
• Concurrent anticoagulant or antiplatelet therapy without clinician oversight due to additive bleeding risk.
• History of atrial fibrillation or atrial flutter: avoid high doses and use only with medical supervision given signal for increased AF at higher intakes.
• Pre-/post-operative periods: many clinicians advise discontinuing higher-dose fish oil 1–2 weeks before elective surgery to minimize bleeding risk, despite mixed evidence.
• Pregnancy and breastfeeding: purified fish oil (EPA/DHA) is generally considered safe; avoid fish liver oil (e.g., cod liver oil) due to vitamin A content; consult a healthcare professional for individualized dosing.
• Markedly elevated LDL-C when using DHA-rich products: monitor lipids or consider EPA-only formulations.