[didymus]

Heres a fairly interesting study re: dosages:

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Distribution, interconversion, and dose response of n–3 fatty acids in humans
Linda M Arterburn, Eileen Bailey Hall and Harry Oken

SUMMARY

Human plasma and tissues are responsive to dietary intake of the long-chain n–3 fatty acids, and levels increase in plasma and tissues in a dose-dependent manner. The most effective way to increase a particular n–3 fatty acid is to provide that specific dietary fatty acid, because interconversion of the n–3 fatty acids is limited in humans. ALA accumulates only to a minor extent, most likely as the result of increased oxidation at higher doses, and modestly raises EPA but not DHA. Plasma phospholipid EPA concentrations increase in a linear manner in response to dietary EPA, whereas dietary DHA causes a dose-dependent, saturable increase in plasma phospholipid DHA concentrations with doses up to {approx}2 g/d. Both DHA and EPA similarly reduce ARA concentrations in plasma. Tissue contents of long-chain n–3 fatty acids increase in response to dietary DHA or EPA. Human milk content of DHA depends on maternal intake of this nutrient, and infant plasma DHA concentrations are responsive to the DHA amounts in their milk or formula feedings. The dose-response information provided herein should be useful in predicting efficient doses of n–3 fatty acids for supplementation studies and for developing recommendations for intakes of specific n–3 fatty acids.

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The relevant point being that DHA appears to be saturable @ 1.2g/d when combined with EPA. This is in contrast to EPA which doesnt appear to saturate. Not sure how much fish oil you're taking currently. I get about 900mg/d DHA and 1800mg/d EPA.