Choosing an omega-3 supplement
Not all fish oil capsules are equal. Concentration, form, freshness and the EPA-to-DHA ratio all matter. Here's how to read a label without getting taken for a ride.
The four common forms
Triglyceride form
Most affordable. Typically 180 mg EPA + 120 mg DHA per 1 g capsule (~300 mg combined). You'll need 3–4 capsules to hit a 1,000 mg/day target.
Pro: cheap. Con: lower concentration means more capsules and more "fishy" reflux.
Re-esterified triglyceride or ethyl ester
Typically 400 mg EPA + 200 mg DHA per cap (~600 mg combined), or higher. Triglyceride form absorbs roughly 50–70% better than ethyl ester (Dyerberg 2010, Prostaglandins, Leukotrienes & Essential Fatty Acids; Neubronner 2011, European Journal of Clinical Nutrition).
Look for "rTG", "triglyceride form" or "natural form" on the label. Higher upfront price — fewer capsules per day.
Phospholipid form
Typically 120 mg EPA + 70 mg DHA per cap (~190 mg combined). Phospholipid form absorbs slightly better per milligram than triglyceride (Ramprasath 2013). Lower total mg per cap, so you'd need around 5–6 caps to match a 1,000 mg/day target. Includes astaxanthin (antioxidant).
Algae oil — triglyceride form
Typically 150 mg EPA + 300 mg DHA per cap (DHA-dominant), or 250–500 mg combined per cap for newer products. Bioequivalent to fish-derived (Arterburn 2008). Look for products listing both EPA and DHA.
The five things to check on a label
- Combined EPA + DHA per serving — not "total fish oil mg". A 1,000 mg fish oil cap might only contain 300 mg of actual EPA+DHA. The active fatty acids are what count.
- EPA-to-DHA ratio — EPA-dominant for mood, inflammation and ratios. Balanced or DHA-dominant for pregnancy, brain and eye.
- Form — triglyceride (rTG, TG, "natural") absorbs better than ethyl ester (EE).
- Third-party testing — look for IFOS, GOED or USP certification. These verify EPA/DHA content, oxidation levels, and contaminant testing (mercury, PCBs).
- Oxidation / freshness — a totox value below 26 is considered fresh (GOED standard). Cheap, old, or poorly-stored fish oil can be rancid — which defeats the purpose entirely.
EPA vs DHA — which should dominate?
| Goal | Profile |
|---|---|
| Mood, depression | EPA-dominant (≥60% EPA per Sublette 2011 meta-analysis) |
| Inflammation, AA:EPA ratio | EPA-dominant |
| Brain, cognition, eye | Balanced or DHA-dominant |
| Pregnancy, infant development | DHA-dominant or balanced |
| General health, cardiovascular | Balanced is fine |
Storage & absorption tips
- Take with a meal containing fat — this can increase absorption up to 3× (Lawson & Hughes 1988, Biochemical and Biophysical Research Communications).
- Refrigerate after opening if oily or liquid; capsules can stay at room temperature away from light.
- Don't buy more than 3 months' supply unless you'll use it that fast — oxidation increases over time.
Red flags on a label
If you see these, walk away
- "Omega-3 1,000 mg" alone, without an EPA/DHA breakdown — usually means total fish oil, not the active fatty acids.
- Very low EPA+DHA per cap (under 200 mg) sold as if "high concentration".
- No third-party testing mentioned anywhere on the label or website.
- Strong fishy smell on opening — a sign of oxidation.
A simple decision rule
Hit your target dose — calculated from the calculator or your test result — using the smallest number of capsules from a third-party-tested, triglyceride-form product.
Cost per gram of EPA+DHA is the real comparison metric — not cost per capsule. A cheap capsule with 100 mg of actives can easily cost more per gram than a premium concentrate.
Keep learning
Know what to take
Your personalised dose in the Omega-3 Index report tells you exactly how much EPA+DHA to take — based on your starting level, not a guess.
Browse tests →Your personalised dose in your report tells you exactly how much EPA+DHA to take, based on your starting level.