A study found that most fish oil supplements sold in New Zealand contained significantly less of the key omega-3 fatty acids (EPA and DHA) than stated on their labels, with only a small number meeting their advertised content.

We analyzed the available evidence on fish oil supplement labels in New Zealand and found that most products contained significantly less of the key omega-3 fatty acids—EPA and DHA—than what was listed on their labels. Only a small number of supplements met their advertised content [1]. This suggests that what’s written on the bottle often doesn’t match what’s inside. The evidence we’ve reviewed so far comes from one study that tested a range of fish oil supplements sold in New Zealand. It showed that many products fell short of their labeled amounts, sometimes by a large margin. This doesn’t mean all supplements are inaccurate, but the pattern points to a common issue. We don’t know why this happens—whether it’s due to manufacturing inconsistencies, poor quality control, or other factors—because the study didn’t investigate causes. For consumers, this means the amount of EPA and DHA you’re getting might be lower than expected, even if the label says otherwise. If you’re taking fish oil for a specific health reason—like supporting heart or brain health—you may not be getting the dose you think you are. We don’t have enough data to say whether this is true for all brands, or if some are more reliable than others. More testing would help clarify which products are trustworthy. For now, the evidence we’ve reviewed leans toward caution when relying on label claims. Practical takeaway: If fish oil is important for your health, consider looking for brands that provide third-party test results or certifications that verify their omega-3 content.