Fish oil does contain omega-6 fatty acids, but only in small amounts. Pure fish oil supplements average about 3.3% omega-6 fatty acids by total fat content, making omega-3s the dominant fat by a wide margin. The omega-6 present in fish oil is not enough to meaningfully shift your overall omega-6 intake or cause concern.
How Much Omega-6 Is in Fish Oil
A laboratory analysis of commercial marine oil supplements published in the Journal of Agricultural and Food Chemistry broke down the fatty acid profiles across different product types. Standard fish oil concentrates contained an average of 3.7% omega-6 fatty acids, while seal oil products came in at 3.3%. For context, the omega-3 content in these same products typically falls between 30% and 50% or higher, depending on the concentration level. So the ratio heavily favors omega-3.
The specific omega-6 fats found in fish oil are mostly arachidonic acid (about 1.5% of total fat) along with trace amounts of linoleic acid and a few other long-chain omega-6 fats. Arachidonic acid plays a role in inflammation, which is partly why people wonder about omega-6 in fish oil. But at these low levels, it’s not a practical concern.
One important exception: fish oil blends that mix marine oil with plant-based oils like evening primrose or borage oil. These plant/fish oil blends averaged 19.9% omega-6, roughly five times more than pure fish oil. The jump comes almost entirely from linoleic acid contributed by the plant oils. If minimizing omega-6 matters to you, check the ingredient list for added plant oils and stick with pure fish oil or fish oil concentrates.
Why the Small Amount Doesn’t Matter
The typical Western diet already delivers far more omega-6 than omega-3, largely from vegetable oils like soybean, corn, and sunflower oil used in cooking and processed foods. A single tablespoon of soybean oil contains around 7 grams of omega-6. A standard fish oil capsule, by comparison, contributes roughly 30 to 40 milligrams. That’s less than 1% of what you’d get from a serving of cooking oil.
The whole point of taking fish oil is to increase omega-3 intake relative to omega-6. Even with its trace omega-6 content, fish oil shifts the balance decisively toward omega-3. Research on fish oil supplementation consistently shows that it lowers arachidonic acid levels in cell membranes, where inflammatory signaling happens. The omega-3 fats (EPA and DHA) effectively displace omega-6 fats from those membranes, which is part of how fish oil exerts its anti-inflammatory effects.
How Omega-3 and Omega-6 Compete in Your Body
Omega-3 and omega-6 fatty acids use the same set of enzymes to be converted into their active forms. These enzymes can only process one type at a time, so the two families are in constant competition. When you consume more omega-3 (especially the long-chain EPA and DHA found in fish oil), those fats occupy more enzyme capacity, leaving less room for omega-6 conversion into inflammatory compounds.
This competition is also why the ratio between the two types matters more than the absolute amount of either one. Humans can’t make omega-3 or omega-6 from scratch. Both must come from food. Fish oil delivers EPA and DHA in their ready-to-use forms, bypassing the conversion bottleneck entirely. That makes it one of the most efficient ways to tip the balance toward omega-3, regardless of the small amount of omega-6 it carries along.
What Fish Oil Labels Do and Don’t Tell You
Most fish oil supplement labels prominently list EPA and DHA content per serving but don’t break out omega-6 levels. Under U.S. regulations, supplement manufacturers must follow FDA labeling requirements and good manufacturing practices that ensure purity and accurate composition, but there’s no specific mandate to disclose omega-6 content on the Supplement Facts panel. Some higher-end brands voluntarily publish full fatty acid profiles, either on the label or through third-party testing certificates on their websites.
If you want to verify omega-6 content, look for brands that provide a Certificate of Analysis (COA). These documents list the complete fatty acid breakdown, including all omega-6 subtypes. Products labeled as “concentrated” or “purified” fish oil tend to have slightly less omega-6 than standard fish oil because the concentration process selectively increases the proportion of EPA and DHA while reducing other fats. The difference is modest, though, since omega-6 levels are already low in any pure fish oil product.
Fish Oil vs. Other Omega-3 Sources
Not all omega-3 supplements have the same omega-6 profile. Krill oil generally has a similar or slightly lower omega-6 percentage compared to fish oil. Algal oil (made from microalgae) is almost exclusively DHA with very little omega-6. Flaxseed oil, on the other hand, contains a meaningful amount of omega-6 alongside its plant-based omega-3 (ALA), typically in a ratio of about 1:3 omega-6 to omega-3.
Among whole foods, fatty fish like salmon, mackerel, and sardines mirror the fatty acid profile of fish oil supplements, with omega-3 dominating and omega-6 present only in small quantities. Walnuts and chia seeds provide omega-3 in plant form but also carry more omega-6 than any marine source. For someone specifically trying to maximize omega-3 while keeping omega-6 low, fish oil and algal oil are the cleanest options.