DHA (C22:6 n-3)

DHA, docosahexaenoic acid, is the structural omega-3. It concentrates in the brain and in the photoreceptor membranes of the retina, where its unusually flexible shape is what allows those membranes to work the way they do.

It is laid down heavily during fetal development and infancy, which is why intake during pregnancy and breastfeeding is treated separately in dietary guidance. In adults it continues to matter for neuroplasticity and for maintaining the membranes already built.

Like EPA, serum DHA reflects recent intake, while the Omega-3 Index reflects what has accumulated in red cell membranes over months.

Below 40 umol/L indicates low circulating DHA. The typical driver is simply not eating oily fish, since there is no efficient alternative route to DHA in the diet.

Conversion from the plant precursor ALA exists but runs at a low percentage, and it falls further when linoleic acid intake is high, which is the norm on a Western diet.

Fat digestion also matters. DHA needs adequate bile flow to be absorbed, so poor fat digestion can produce a low result despite reasonable intake.

Between 40 and 290 umol/L your circulating DHA sits inside the reference range for this panel.

The reference range is wide because DHA varies a great deal with recent intake. A single fish meal in the days before the draw moves it, which is worth knowing when comparing two results.

Above 290 umol/L usually reflects high-dose supplementation, often from a high-DHA formulation or cod liver oil taken alongside another omega-3 product.

Very high combined omega-3 intakes extend bleeding time, and cod liver oil brings vitamin A with it, so a high DHA result from that source is a reason to check total vitamin A intake as well.

Review your total intake across all sources and discuss it with your practitioner if you take medication affecting clotting.

DHA depletion tracks the decline in oily fish consumption. Because DHA is structural rather than signalling, the consequences accumulate quietly over years rather than showing up as an acute change.

High linoleic acid intake from seed oils suppresses what little conversion from plant precursors would otherwise occur, so the Western pattern reduces both the direct supply and the fallback route.

Wild-caught fatty fish two to three times weekly is the direct source. Cod liver oil is the traditional concentrated form and supplies vitamins A and D alongside.

Pastured eggs contribute, and DHA-enriched eggs more so. Grass-fed beef and organ meats supply smaller amounts.

Support fat digestion with bitter greens and adequate dietary fat, since absorption depends on bile flow.

High-DHA fish oil supplying 1 to 2 g DHA daily where the goal is to raise this marker specifically.

Algae-derived DHA at 500 to 1,000 mg daily is the plant-based route, and it supplies DHA directly rather than relying on conversion.

Take with a meal containing fat. Triglyceride-form products absorb better than ethyl ester.