How Much DHA Do You Actually Need Per Day?

The claim dose and the trial dose are different numbers

The GB claims register lets a label say DHA maintains normal brain function at 250 mg a day. The trials that moved something you could measure used four to fourteen times that.

Both numbers are honest. They answer different questions.

250 mg is the intake at which regulators accepted the evidence for maintenance — keeping a normal function normal. It is a floor. The muscle, triglyceride and blood-level trials ran at 1.2 g to 3.4 g a day of EPA plus DHA combined.

So the question splits in two. If you want the authorised claim to apply to you, 250 mg of DHA does it. If you want the effect sizes the trials reported, you need a bigger number, and the number is not the same for everyone.

What each dose did to blood levels

Flock and colleagues gave 115 healthy adults 0, 300, 600, 900 or 1,800 mg of EPA plus DHA a day for about five months. All of them ate little oily fish to start with. Their mean omega-3 index — the share of red blood cell fat made up of EPA and DHA — was 4.3%.

Dose alone explained 68% of the variation in response. The 300 mg group reached a median index of 6.1%. The 900 mg group reached 7.6%. The 1,800 mg group reached 9.9%.

The line that matters is this one: nobody on 600 mg a day or less reached an index of 8%.

If your target is an index around 8%, the 250 mg on the bottle is not the dose that gets you there.

Plants will not get you there

The plant omega-3 is ALA, from flax, chia and walnuts. Your body can convert it. The question is how much.

Burdge and Wootton fed young women a labelled ALA tracer and followed it for 21 days. Net conversion was 21% to EPA, 6% to DPA and 9% to DHA. That is the generous result.

The same group ran the same method in young men. They found no labelled DHA in plasma at any point over 21 days. The authors concluded the capacity was very low or absent.

Arterburn's review of the distribution data reached the same practical conclusion. The reliable way to raise a specific long-chain omega-3 is to eat that fatty acid. If you take no fish and no algae, your DHA intake is close to zero regardless of how much flax you add. We covered the numbers for plant-only diets in our vegan omega-3 guide.

The chemical form changes the arithmetic

Most concentrated fish oils are ethyl esters. The fatty acid is bolted to an ethanol backbone, which is cheaper to concentrate. Natural fish oil and most algae oil are triglycerides.

Neubronner ran 150 people for six months on identical doses — 1.01 g EPA plus 0.67 g DHA a day — as either re-esterified triglyceride or ethyl ester. The triglyceride group finished at 197% of their baseline index. The ethyl ester group finished at 171%.

Walker's pooled analysis of 1,422 people found the same direction. Gram for gram, triglyceride products raised the index by about one percentage point more than ethyl esters.

One percentage point sounds small. On a scale where 4% is typical and 8% is the target, it is a quarter of the journey.

Fat in the meal decides how much arrives

This is the cheapest fix on the list and almost nobody does it.

Lawson and Hughes measured absorption from a meal containing 8 g of fat, then repeated it with 44 g. Ethyl ester absorption roughly tripled, to about 60%. Triglyceride-form EPA rose from 69% to 90%.

The mechanism is pancreatic lipase. It is released in response to dietary fat, and it is what cleaves the fatty acid off its backbone. No fat in the meal, less lipase, less absorbed.

A capsule with black coffee is close to the worst case. A capsule with eggs, or with dinner, is close to the best. That is a free 20 to 200% depending on which oil you bought.

Body weight sets your number

The Flock team found that dose per kilogram of body weight predicted response better than dose alone — 70% of the variation against 68%. Bigger people need more of it for the same blood level.

Using their model, an adult starting at an index of 4.3% would need roughly 0.9 g a day at 55 kg, 1.2 g at 75 kg and 1.5 g at 95 kg. Those are modelled figures, not measured ones, so treat them as a starting point rather than a prescription.

Two other things shifted the response. A lower starting index predicted a bigger rise. So did being older, though that effect was small in a cohort aged 20 to 45.

The practical version: if you are 90 kg and lifting four times a week, the standard capsule was not designed with you in mind.

The doses where specific things happened

Round numbers are easier to remember than they are to justify. Here is what specific doses produced in specific trials.

3.4 g a day, muscle. Smith randomised 60 adults aged 60 to 85 to 1.86 g EPA plus 1.5 g DHA daily, or corn oil, for six months. Among the 44 who completed, thigh muscle volume rose 3.6%, grip strength 2.3 kg and one-rep max 4% against control. No training programme was involved.

2 to 3 g a day, triglycerides. A dose-response meta-analysis of 90 trials in 72,598 people found triglycerides fell 42.6 mg/dL at 2 g a day and 68.9 mg/dL at 3 g. In UK units that is roughly 0.48 and 0.78 mmol/L. The relationship was close to linear across the range.

250 mg a day, the claim. Brain function and vision, DHA alone. Heart function needs 250 mg of EPA plus DHA combined.

2 g and 3 g, the higher claims. The register permits a normal blood triglyceride claim at 2 g of DHA a day, and a normal blood pressure claim at 3 g of EPA plus DHA. Almost no single-capsule product reaches either.

None of these are promises about what will happen to you. They are what those groups recorded on those doses.

Four months, then judge it

Red blood cells live about 120 days. Your omega-3 index is a rolling average of what you have been eating for roughly that long, which is exactly why it is useful and exactly why it is slow.

In Walker's pooled data, 846 supplemented people took a mean of 1,983 mg a day for an average of 13.6 weeks. The index moved from 4.9% to 8.1%.

Three weeks of capsules tells you nothing. If you are going to test, test at baseline and again at four months, and change nothing in between.

What most people here are actually starting from

The National Diet and Nutrition Survey put mean adult oily fish intake at 54 to 87 g a week. The recommendation is 140 g — one portion. The NHS asks for two portions of fish a week, one of them oily.

So the average British adult is eating roughly half a portion of oily fish a week. That is the baseline behind an index of 4% to 5%, and it is the reason the dose-response curve above starts where it does.

If you already eat salmon or mackerel three times a week, your gap is small and a modest dose closes it. If you eat none, you are starting from the bottom of that chart.

What we would actually do

Decide what you are buying it for first. For the authorised claim and nothing more, 250 mg of DHA a day is the number, and a small capsule covers it.

For the blood level the outcome research is built around, work from your weight: roughly 1 g a day at 55 to 65 kg, 1.2 to 1.5 g at 75 to 95 kg, of EPA plus DHA combined. Check the label gives you that in DHA and EPA, not in "fish oil".

Then take it with a meal that has fat in it, prefer a triglyceride oil to an ethyl ester if you can read which it is, and leave it four months before you decide whether anything changed. If you want the split between the two molecules, we set that out in DHA vs EPA, and the age-specific priorities in omega-3 after 50.

One honest caveat. Higher blood levels are a better marker of intake than they are of outcome, and the large outcome trials at around 1 g a day have been mixed. Getting to an index of 8% is a defensible target. It is not a guaranteed result.

References

1. Flock MR, Skulas-Ray AC, Harris WS, Etherton TD, Fleming JA, Kris-Etherton PM (2013). "Determinants of erythrocyte omega-3 fatty acid content in response to fish oil supplementation: a dose-response randomized controlled trial." Journal of the American Heart Association, 2(6), e000513. PMID: 24252845.
2. Walker RE, Jackson KH, Tintle NL, Shearer GC, Bernasconi A, Masson S, et al. (2019). "Predicting the effects of supplemental EPA and DHA on the omega-3 index." American Journal of Clinical Nutrition, 110(4), 1034-1040.
3. Burdge GC, Wootton SA (2002). "Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women." British Journal of Nutrition, 88(4), 411-420. PMID: 12323090.
4. Burdge GC, Jones AE, Wootton SA (2002). "Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men." British Journal of Nutrition, 88(4), 355-363. PMID: 12323085.
5. Arterburn LM, Hall EB, Oken H (2006). "Distribution, interconversion, and dose response of n-3 fatty acids in humans." American Journal of Clinical Nutrition, 83(6 Suppl), 1467S-1476S. PMID: 16841856.
6. Neubronner J, Schuchardt JP, Kressel G, Merkel M, von Schacky C, Hahn A (2011). "Enhanced increase of omega-3 index in response to long-term n-3 fatty acid supplementation from triacylglycerides versus ethyl esters." European Journal of Clinical Nutrition, 65(2), 247-254. DOI: 10.1038/ejcn.2010.239.
7. Lawson LD, Hughes BG (1988). "Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal." Biochemical and Biophysical Research Communications, 156(2), 960-963. PMID: 2847723.
8. Smith GI, Julliand S, Reeds DN, Sinacore DR, Klein S, Mittendorfer B (2015). "Fish oil-derived n-3 PUFA therapy increases muscle mass and function in healthy older adults." American Journal of Clinical Nutrition, 102(1), 115-122. DOI: 10.3945/ajcn.114.105833.
9. Wang T, Zhang X, Zhou N, Shen Y, Li B, Chen BE, Li X (2023). "Association between omega-3 fatty acid intake and dyslipidemia: a continuous dose-response meta-analysis of randomized controlled trials." Journal of the American Heart Association, 12(11), e029512. PMID: 37264945.
10. Public Health England and Food Standards Agency (2016). "National Diet and Nutrition Survey: results from Years 5 and 6 (combined) of the Rolling Programme (2012/13 - 2013/14)."
11. Department of Health and Social Care (2026). "Great Britain nutrition and health claims (NHC) register." Updated 19 May 2026.
12. NHS (2025). "Fish and shellfish." NHS Live Well: Eat Well.

Work out your number, then read the label

Our algae oil is DHA-led and supplied in triglyceride form. Whatever you buy, check the DHA per serving against the doses in this article, and check whether the oil is a triglyceride or an ethyl ester. Both numbers change what actually reaches your cells.

See Omega-3 DHA →