Both provide omega-3 fatty acids (EPA and DHA). The debate over which is "better" often ignores what matters most: how much EPA and DHA you're actually getting for your money.
Fish Oil
What it is: Oil extracted from fatty fish (salmon, mackerel, anchovies, sardines)
EPA/DHA content: High. Quality products provide 500-1000mg EPA+DHA per capsule.
Absorption: Good, especially in triglyceride form (vs ethyl ester)
Pros: - Much more research (thousands of studies) - Higher EPA/DHA per serving - More cost-effective - Easier to reach therapeutic doses
Cons: - Fish burps in low-quality products - Larger capsules - Environmental concerns (source matters)
Krill Oil
What it is: Oil from small Antarctic crustaceans (krill)
EPA/DHA content: Lower. Typically 100-200mg EPA+DHA per capsule.
Absorption: Possibly better. Omega-3s are bound to phospholipids rather than triglycerides, which may improve uptake.
Pros: - No fish burps - Smaller capsules - Contains astaxanthin (antioxidant) - May absorb better per mg
Cons: - Much more expensive per mg of omega-3 - Less EPA/DHA per serving - Harder to reach therapeutic doses - Less research overall
The Math
Let's say you want 1000mg EPA+DHA daily:
Fish oil: 1-2 capsules, ~$0.20-0.40/day
Krill oil: 4-6+ capsules, ~$1.50-2.00/day
Even if krill absorbs 50% better (generous estimate), fish oil still wins on value. You can just take more fish oil for less money.
Exception: If fish oil causes burps or nausea that you can't solve with quality or freezing capsules, krill oil may be worth the premium.
How to Choose
Pick fish oil if: - Cost matters - You want therapeutic doses (1-3g) - You're willing to choose quality products
Pick krill oil if: - Fish oil causes digestive issues - You prefer smaller pills - Cost isn't a concern
Best fish oil tips: - Choose triglyceride form over ethyl ester - Look for third-party testing (IFOS certification) - Store in freezer to prevent burps - Take with food
The Bottom Line
For most people, quality fish oil is the better choice. More EPA/DHA, more research, lower cost. Krill oil is fine but often overhyped relative to its higher price.