Evidence indicates that n-3 fatty acids exert several beneficial effects. However, the effects of marine n-3 fatty acids on intermediary metabolism have not been completely elucidated. In a previous study of a high intake of marine n-3 fatty acids during 9 wk we demonstrated reduced insulin sensitivity and altered proportion of carbohydrate vs. fat oxidation in subjects with type 2 diabetes. These results question the use of high doses of n-3 supplements in type 2 diabetes. It is not known to what extent such effects in type 2 diabetes can be reproduced by intravenous administration of n-3 fatty acids and/or whether short term intravenous administration has other effects.