Krill oil wins on bioavailability and antioxidant content; fish oil wins on EPA/DHA concentration and value. For cost-effective high-dose omega-3 therapy, fish oil is superior. For lower doses with potentially enhanced absorption and added astaxanthin, krill oil is compelling.
Overview
Fish oil and krill oil both deliver EPA and DHA omega-3 fatty acids — but they differ in molecular form (triglyceride vs phospholipid), concentration, additional antioxidant content, and cost. Here's the evidence-based breakdown.
What Is Fish Oil?
Omega-3 fatty acids in triglyceride form from oily fish. Contains EPA and DHA at high concentrations. The most extensively studied omega-3 supplement with decades of cardiovascular research.
Best for: High-dose EPA/DHA therapy, Cardiovascular disease risk, Triglyceride reduction, Depression (EPA-dominant formulas).
Standard dose: 1–4 g EPA+DHA/day depending on goal.
Side effects: Fishy burps, GI upset. Oxidation risk if stored improperly. Blood-thinning at high doses..
What Is Krill Oil?
Oil from Antarctic krill (Euphausia superba). EPA and DHA are in phospholipid form rather than triglyceride form, potentially improving incorporation into cell membranes. Contains the powerful antioxidant astaxanthin which also protects the oil from oxidation.
Best for: People who experience fishy burps with fish oil, Those wanting antioxidant (astaxanthin) co-benefits, Lower-dose omega-3 supplementation, Women — phospholipid form may preferentially support brain DHA.
Standard dose: 500–1,000 mg krill oil/day (delivering ~100–250 mg EPA+DHA — much less than fish oil per capsule).
Side effects: Generally better tolerated than fish oil. Shellfish allergy contraindication. More expensive..
Evidence & Absorption Scores
We scored both on four dimensions: quality of clinical evidence, bioavailability, GI tolerance, and value for money. Scores are out of 10:
Head-to-Head Comparison
| Category | ▲ Fish Oil | ▲ Krill Oil |
|---|---|---|
| EPA+DHA Per Capsule | High — typically 600–1,200 mg EPA+DHA | Low — typically 100–250 mg EPA+DHA |
| Bioavailability | Good (TG form) to Excellent (rTG) | Potentially superior per mg (phospholipid) |
| Antioxidant Content | None naturally (some add vitamin E) | Contains astaxanthin — powerful antioxidant |
| Fishy Taste/Burps | Common complaint | Rarely reported |
| Oxidation Stability | Can oxidise — store carefully | More stable due to astaxanthin |
| Allergen Risk | Fish allergy | Shellfish (crustacean) allergy |
| Cost per gram EPA+DHA | Low — most economical | Very high — 3–5× more expensive |
| Clinical Evidence Depth | Extensive (thousands of studies) | Growing but limited vs fish oil |
Best Uses for Each
✅ Fish Oil — Best For
- High-dose EPA/DHA therapy
- Cardiovascular disease risk
- Triglyceride reduction
- Depression (EPA-dominant formulas)
✅ Krill Oil — Best For
- People who experience fishy burps with fish oil
- Those wanting antioxidant (astaxanthin) co-benefits
- Lower-dose omega-3 supplementation
- Women — phospholipid form may preferentially support brain DHA
Who Should Choose Fish Oil?
▲ Choose Fish if:
Anyone wanting to maximise EPA+DHA intake cost-effectively, especially for therapeutic doses (triglyceride reduction, cardiovascular protection, depression). Buy rTG or TG form fish oil from a reputable brand with third-party testing.
▲ Choose Krill if:
People who experience intolerable fishy burps with fish oil, those wanting astaxanthin co-benefits, or people comfortable with lower omega-3 doses. Krill oil is also a reasonable choice if sustainability is a priority (krill is one of the most sustainably harvested marine organisms).
Can You Take Both?
Generally not necessary — choose one and stick with it. If you find fish oil causes GI issues but still want higher EPA+DHA doses, switch to an enteric-coated fish oil before defaulting to krill.
Frequently Asked Questions
The Bottom Line
Krill oil wins on bioavailability and antioxidant content; fish oil wins on EPA/DHA concentration and value. For cost-effective high-dose omega-3 therapy, fish oil is superior. For lower doses with potentially enhanced absorption and added astaxanthin, krill oil is compelling.