The cardiovascular benefits of omega-3 polyunsaturated fatty acids (O3FA) remain a point of confusion in clinical medicine. Recently two large, randomised trials were published with discordant findings regarding the overall benefits of omega-3 supplementation, resulting in unnecessary confusion and therapeutic nihilism. Epidemiological studies clearly show high intake of fish and measured O3FA (mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) in tissues are inversely associated with cardiovascular events and total mortality. These fatty acids are ‘essential’ and depend almost entirely on intake with very little production from within the body. The efficacy of supplementation depends on background tissue levels, in contradistinction to drug therapy. Insufficient dosing of omega-3 supplementation using less than 1 g/day and lack of titration to target by failing to measure O3FA levels in the blood may explain these conflicting trial outcomes. We review the current evidence regarding O3FA supplementation and cardiovascular outcomes, describe possible reasons for the discrepant results in the literature including recent controversial data around the mineral oil comparator used in REDUCE-IT and discuss the potential use of the omega-3 index to guide management and optimise supplementation in those at greatest risk.