How to choose a fish oil supplements
Updated June 2026Independently researchedNo paid placement.
To choose a fish oil supplement, focus on the total EPA plus DHA content per serving (not just fish oil weight), pick a reputable brand that tests for purity and freshness (low TOTOX and oxidation values), and decide whether standard fish oil, concentrated forms, or krill oil best fits your budget and digestion needs. Avoid vague labels and go for third-party certified products when possible.
How much epa and dha should a fish oil supplement have?
The two omega-3s that matter most are EPA and DHA. What you see on the front of the bottle (e.g., 1000 mg fish oil) is not what you get in beneficial fats, check the supplement facts panel for the actual milligrams of EPA plus DHA. For general wellness, most nutrition experts suggest a combined intake of 500–1000 mg per day, but therapeutic needs (like supporting joint health or triglycerides) may call for 2000–3000 mg or more. Higher-concentration oils mean you can take fewer softgels, but they often cost a bit more per milligram. The sweet spot for most people is a formula that delivers at least 600–800 mg total EPA/DHA per serving.
Fish oil vs. krill oil: which one is right for you?
Krill oil comes from tiny crustaceans rather than fatty fish like anchovies or sardines. Its omega-3s are mostly attached to phospholipids, which some research suggests may be absorbed more efficiently than the triglyceride form in standard fish oil. Krill oil also naturally contains astaxanthin, a powerful antioxidant that helps keep the oil stable. The trade-off: krill oil typically has much lower EPA and DHA per serving than a comparable fish oil softgel (often around 200 mg total per capsule) and is usually more expensive. If you have trouble swallowing large pills or get fishy burps from regular fish oil, krill can be gentler. For high-dose omega-3 needs, concentrated fish oil is usually more cost-effective.
What forms of fish oil are best absorbed?
The chemical form matters for how well your body uses the omega-3s. Most natural fish oil comes as triglycerides (rTG). Some less expensive brands use ethyl esters (EE), which are slightly less bioavailable – though the difference is small enough that many people still benefit. Better-quality supplements go a step further and re-esterify the oil back to triglyceride form (rTG), which improves absorption and reduces oxidation. If you’re new to supplements, a high-quality rTG formula is a safe bet. For budget-conscious buyers, a reputable EE product is still effective if the total EPA/DHA dose is adequate.
How to check for purity and freshness in fish oil?
Fish oil can go rancid, that fishy aftertaste or burp is often a sign of oxidation. Look for products that display a total oxidation value (TOTOX) on the label or certificate of analysis. The Global Organization for EPA and DHA Omega-3s (GOED) sets a voluntary standard of TOTOX ≤ 26. Anything lower than 20 is excellent. Reputable brands either publish their third-party test results or provide a lot number you can search online. Also check for purity certifications: the International Fish Oil Standards (IFOS) program is one of the most rigorous, testing for PCBs, dioxins, heavy metals, and oxidation simultaneously. If a product is IFOS-certified, you can trust it’s clean and fresh even if the price is a few dollars higher.
Should you choose a fish oil softgel or a liquid bottle?
Softgels are convenient: pre-measured, portable, and usually tasteless if you swallow them quickly. But they often require multiple capsules per day to reach a therapeutic dose, and some people find them hard to swallow. Liquid forms let you adjust your dose easily and often provide more EPA/DHA per spoonful, which may save money. The downside is the taste – even lemon-flavored liquids can leave a fishy burp if you’re sensitive. If you prefer liquid, refrigerate it after opening and use it within the bottle’s recommended window (usually two to three months). For travel or daily forgetfulness, softgels win.
What about sustainability and sourcing?
Not all fish oil is harvested responsibly. Overfishing of large predators like tuna can harm marine ecosystems. Better brands use anchovies, sardines, or small pelagic fish that reproduce quickly and are less likely to be overfished. Look for certifications from the Marine Stewardship Council (MSC) or Friend of the Sea. Some brands also use wild Alaskan salmon oil or sustainably farmed algal oil (a vegan option). Krill oil’s environmental impact is more debated because krill is a keystone species in the Antarctic ecosystem – choose brands certified by the Marine Stewardship Council or the Antarctic Krill Conservation Project to help ensure responsible catch limits.
Frequently asked questions
Can I take fish oil on an empty stomach?
It’s better to take fish oil with a meal that contains fat, because fat aids absorption and reduces the chance of fishy burps or stomach upset. Taking it with food may also improve the EPA/DHA blood levels you get from the same dose.
How long does it take for fish oil to work?
Omega-3s build up in your tissues over weeks, not days. Many people notice improvements in joint comfort or mood stability after six to twelve weeks of consistent use. For blood triglyceride levels, effects often appear within three to six months.
Does fish oil thin your blood or interact with medications?
High-dose fish oil (above 3000 mg EPA/DHA combined) can have a mild blood-thinning effect. If you take blood thinners like warfarin or have upcoming surgery, check with your doctor before adding a supplement. Standard over-the-counter doses (1000–2000 mg) are generally safe but always disclose use to your healthcare provider.
What is the difference between molecularly distilled fish oil and regular?
Molecular distillation is a purification process that separates the omega-3s from contaminants like PCBs, dioxins, and mercury using high heat and vacuum. Most quality fish oils are molecularly distilled – it’s a sign of purity. Cheaper oils may not be distilled, so they carry a higher risk of toxin build-up.
Is it safe to take fish oil every day?
Yes, for most people daily use is safe and recommended to maintain omega-3 levels. The European Food Safety Authority considers up to 5000 mg total EPA plus DHA per day safe for adults. Always stay within label dosing unless advised otherwise by a doctor.
Should I refrigerate my fish oil softgels?
Refrigeration is not required for most softgels, but it can extend their shelf life and reduce the risk of oxidation. Liquid fish oil should be refrigerated after opening. Keep all supplements away from direct sunlight and heat to preserve freshness.