Reading omega-3 labels: EPA, DHA, and the ratio that actually matters

A "1,000 mg fish oil" softgel rarely delivers 1,000 mg of omega-3s. That number is total oil weight, of which only a fraction is the long-chain omega-3s EPA and DHA. The amounts shown for EPA and DHA on the Supplement Facts panel are what matters, and those are what controlled trials are usually dosed around.

The front-of-bottle number is not the dose

A typical "1,000 mg fish oil" softgel contains 18 percent EPA and 12 percent DHA — about 180 mg EPA and 120 mg DHA per capsule, for a total of 300 mg of long-chain omega-3s. To match the 1 g/day omega-3 doses used in legacy trials like GISSI-Prevenzione, a person needs 3–4 of these capsules. To match the 4 g/day dose used in REDUCE-IT, 12–16 capsules per day — which is why prescription esters exist. Concentration markedly varies; "concentrated" or "triple-strength" products can deliver 600+ mg combined EPA+DHA per softgel.

EPA:DHA ratio and indication

Trials in different indications used different ratios. Pure EPA (icosapent ethyl, the REDUCE-IT formulation at 4 g/day) reduced cardiovascular events in statin-treated patients with persistent hypertriglyceridaemia (PMID: 30415628).¹ A mixed EPA:DHA carboxylic acid (STRENGTH) did not (PMID: 33190147).² For triglyceride lowering specifically, both EPA-only and mixed preparations reduce triglycerides at 4 g/day, but EPA-only does so without raising LDL-C, which mixed EPA+DHA formulations can. For depression adjunctive therapy, a 2019 meta-analysis suggested that EPA-predominant formulations (EPA:DHA >2:1) with at least 60 percent EPA produced the clearest mood effects, while DHA-predominant products did not (PMID: 30989183).³ For pregnancy and infant brain development, DHA is the relevant species, and at least 200 mg/day of DHA is the consensus prenatal recommendation (PMID: 38540527).⁴

Ester forms: triglyceride, ethyl ester, free fatty acid, phospholipid

Fish oil capsules contain omega-3s in one of four forms. Natural-source triglyceride (TG) form is what fish actually contain. Ethyl ester (EE) is a synthetic form used by Lovaza and many concentrates because it allows higher concentration but produces somewhat lower bioavailability — about 70 percent of TG-form absorption when taken without a fatty meal (PMID: 20861171).⁵ Free fatty acid (FFA) form (Vascepa, Epanova) has the highest fasted bioavailability. Phospholipid form (krill oil) is intermediate in plasma omega-3 response per gram of EPA+DHA but has not been shown to deliver superior clinical outcomes in head-to-head trials (PMID: 33933036).⁶

Quality markers that actually matter

The IFOS, USP, and EPAX quality programs verify product label accuracy, oxidation markers (peroxide and anisidine values), and heavy metal/PCB content. The 2024 ConsumerLab analysis found that roughly 15 percent of tested fish oil products fell outside IFOS oxidation thresholds, with most failures in low-priced softgels (PMID: 38947532, secondary reference).⁷ Oxidised omega-3 not only loses biological activity; it may produce pro-inflammatory aldehydes. The IFOS 5-star rating includes oxidation as a hard pass/fail criterion.

How to compare two products in 60 seconds

Ignore the front-of-bottle weight. Look at the Supplement Facts panel and find combined EPA+DHA per serving. Divide by capsule count to get per-capsule omega-3. Compare price per gram of EPA+DHA, not per bottle. Check the ester form (TG, EE, FFA, or PL) and confirm a third-party purity certification (IFOS, USP, or NSF). Most consumer choices come down to TG-form fish oil at ~60 percent omega-3 concentration with IFOS certification at the lowest price per gram, or EE-form at higher concentration when convenience matters more than per-gram cost. Vegan algal oil provides comparable EPA+DHA (the algal source DHA, ALA-poor) at higher per-gram cost (PMID: 35458187).⁸