Omega-3 Supplements: Benefits, Dosage and How to Choose
Omega-3 supplements provide EPA and DHA, fats your body uses for cell membranes, heart rhythm and brain function. They clearly lower high triglycerides; other benefits are smaller or less certain. For general health, 250–500 mg of combined EPA + DHA a day is a common target, which two servings of fatty fish a week also provide.
Evidence at a glance
| Use | Grade | What the research shows |
|---|---|---|
| Lowering high triglycerides | A | 2–4 g/day of prescription EPA/DHA lowers triglycerides substantially. |
| Heart disease prevention (general population) | C | Large trials show mixed results; benefits seem larger in people who eat little fish. |
| Rheumatoid arthritis symptoms | B | Modest reductions in joint pain and stiffness in several trials. |
| Depression (EPA-rich) | C | Some meta-analyses suggest a small benefit as an add-on; evidence is inconsistent. |
A: strong, consistent human evidence · B: moderate · C: limited or mixed · D: good evidence of no benefit.
There are three main omega-3s. ALA comes from plants such as flax and walnuts. EPA and DHA come mainly from fish and algae, and they're the ones linked to most health benefits. The body converts only a small fraction of ALA into EPA and DHA, so supplements focus on the latter two.
Sources compared
| Source | EPA + DHA per capsule | Notes |
|---|---|---|
| Concentrated fish oil | 500–900 mg | Best value per mg |
| Standard fish oil | about 300 mg | Large capsules |
| Krill oil | 100–250 mg | Small capsules, higher cost |
| Algal oil | 200–500 mg (mostly DHA) | Vegan option |
| Cod liver oil | about 200 mg | Also contains vitamins A and D |
We compare the two most common options in fish oil vs krill oil.
How to choose a good product
- Read EPA + DHA per serving, not "total fish oil"
- Look for third-party purity testing (IFOS, USP or NSF)
- Choose sustainably sourced oil (MSC or Friend of the Sea)
- Avoid oil that smells strongly rancid
Safety
Common side effects are fishy burps, heartburn and loose stools; taking omega-3s with food helps. High doses may slightly increase bleeding risk with anticoagulants, and trials have linked high-dose omega-3s to a small rise in atrial fibrillation in people with heart risk factors. Ask your doctor before taking more than 2 g a day.
Sources
This page is for education and is not a substitute for advice from your doctor. Read our medical disclaimer.