How Many Carbs Are in Omega-3 Fatty Acids?

December 31, 2025 •

3 min read

According to the U.S. Office of Dietary Supplements, there are zero carbohydrates in the omega-3 fatty acids found in fish oil. As a category of polyunsaturated fat, pure omega-3s are a source of fat, not carbohydrates, making them a staple in low-carb diets like keto. However, the total carbohydrate count can change depending on the food or supplement source.

Quick Summary

Pure omega-3 fatty acids, like EPA and DHA, are fat molecules and contain no carbs. The total carbohydrate content depends on the food or supplement in which they are consumed. Some sources, like chia seeds, contain both fiber and net carbs, while fish oil supplements are typically carb-free.

Key Points

Omega-3 Is a Fat: As a fatty acid, the omega-3 molecule itself is chemically a fat, containing zero carbohydrates.
Supplements Are Typically Carb-Free: Most fish oil and algal oil supplements are purified fats and have zero grams of carbohydrates.
Foods Can Contain Carbs: While fatty fish is carb-free, plant-based sources like seeds and nuts include other nutrients, including carbohydrates.
Net Carbs in Plant Sources: In seeds like chia and flax, most of the carbs are fiber, resulting in a very low net carb count.
Ideal for Keto: Due to their zero or low-carb nature, omega-3 sources are perfect for ketogenic and low-carb diets to maintain fat intake.
Read Labels: Always check the nutrition facts on supplements and fortified foods, as additives can sometimes contain small amounts of carbohydrates.
Combine Sources: Incorporate both fatty fish (carb-free) and mindful portions of plant sources like walnuts and chia seeds to get a range of omega-3 types.

The Core Truth: Omega-3 is a Pure Fat

From a chemical standpoint, omega-3s are fatty acids, which are a type of lipid. The three primary types relevant to human health are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). Fatty acids are constructed from chains of carbon atoms and do not contain any carbohydrate structures, such as glucose or fructose. This fundamental distinction means that pure omega-3 fatty acids inherently contain zero grams of carbohydrates.

Carb-Free Omega-3 in Supplements

For those on strict low-carb or ketogenic diets, fish oil, cod liver oil, krill oil, and algal oil supplements are excellent sources of pure omega-3s without any accompanying carbohydrates. Most reputable supplement manufacturers ensure their products contain only the purified fats. It is always wise, however, to check the nutrition facts label on your specific supplement. Inactive ingredients or the capsule material could potentially add a trace amount of carbohydrates, but this is extremely rare and typically negligible.

Carbs in Food Sources of Omega-3

While pure omega-3 is carb-free, the foods rich in this essential fat often contain other macronutrients, including carbohydrates. It is crucial to understand the full nutritional profile of your food sources to avoid compromising a low-carb diet.

Fatty Fish: Fish like salmon, mackerel, and sardines are packed with EPA and DHA and contain zero carbohydrates. They are primarily a source of fat and protein.
Plant-Based Seeds: Chia seeds and flaxseeds contain significant amounts of ALA, but also a notable amount of carbohydrates. Most of these carbs, however, are in the form of dietary fiber, which is not digested by the body and does not impact blood sugar. The remaining 'net carbs' are generally low.
Nuts: Walnuts, which are a good source of ALA, also contain carbohydrates, though typically a moderate amount that can be managed within a controlled diet.

Low-Carb vs. No-Carb Omega-3 Sources

Carbohydrate Comparison of Common Omega-3 Sources (per 1 ounce/28g serving)


Source	Omega-3 Content	Total Carbs (g)	Fiber (g)	Net Carbs (g)
Salmon Fillet	High (EPA/DHA)	0	0	0
Sardines	High (EPA/DHA)	0	0	0
Mackerel	High (EPA/DHA)	0	0	0
Flaxseeds	High (ALA)	~8	~8	0
Chia Seeds	High (ALA)	~12	~10	~2
Walnuts	Medium (ALA)	~4	~2	~2

This table highlights the clear distinction between animal-based and plant-based omega-3 sources concerning their carbohydrate content. While fish offers pure fat, seeds and nuts offer a combination of fiber and fats. For those tracking net carbs, the fiber content of seeds effectively lowers their glycemic impact.

The Keto and Low-Carb Perspective

Because omega-3s are a pure fat, they are a highly valuable macronutrient for individuals following a ketogenic or low-carb lifestyle. Including fatty fish and carb-free supplements can help maintain the high-fat intake required for ketosis without adding unwanted carbohydrates. For plant-based individuals or those seeking more variety, ALA sources like chia seeds and flaxseeds can be excellent, provided the net carb count is factored into daily totals.

Making Smart Choices for Your Diet

To maximize your omega-3 intake while managing carbohydrates, the following strategy is recommended:

Prioritize fatty fish: Make oily fish, such as salmon, mackerel, and sardines, a weekly staple. They provide a direct, carb-free source of EPA and DHA.
Supplement wisely: Choose a high-quality fish oil, krill oil, or algal oil supplement if dietary intake is insufficient. Always verify the nutrition label to confirm a zero-carb profile.
Consider plant sources strategically: Utilize ALA-rich sources like chia seeds and walnuts, but be mindful of their carbohydrate contribution, even if it's primarily fiber. A tablespoon of ground flaxseed contains practically zero net carbs and is a great addition to salads or smoothies.

Conclusion: Omega-3 is Carb-Free, Sources Vary

In essence, the omega-3 fatty acid molecule itself is entirely devoid of carbohydrates. This is why fish oil and similar supplements are perfect for zero-carb and low-carb diets. However, when choosing food sources, it is essential to look at the complete nutritional profile. Fatty fish is a carb-free omega-3 source, while plant-based sources like seeds and nuts contain varying amounts of carbohydrates and fiber. By understanding this distinction, you can easily incorporate this healthy fat into any diet, including keto, without affecting your carb goals. For more in-depth information on fatty acids and their health implications, refer to the National Institutes of Health Office of Dietary Supplements.

This article is for informational purposes only and should not be considered medical advice. Always consult with a healthcare professional before making changes to your diet or taking supplements.

Frequently Asked Questions

Most high-quality omega-3 supplements like fish oil, cod liver oil, or algal oil contain no carbohydrates, as they are purified fats. However, it is always best to check the specific product's nutrition label to be certain.

No, pure fatty fish such as salmon, mackerel, and sardines contain zero carbohydrates. They are excellent sources of protein and omega-3 fats, making them ideal for low-carb diets.

Yes, chia seeds contain carbohydrates, but they are also very high in dietary fiber. The net carb count (total carbs minus fiber) for chia seeds is quite low, making them a suitable plant-based option for low-carb diets.

Absolutely. Omega-3 fatty acids, especially from carb-free sources like fatty fish and pure supplements, are highly recommended for the keto diet. They help maintain the high-fat intake necessary for ketosis.

The omega-3 molecules themselves (ALA, EPA, and DHA) are all pure fats and contain no carbs. The distinction in carbohydrate content comes from the source: EPA and DHA come from fish (carb-free food), while ALA comes from plants (foods with fiber and carbs).

No, pure fish oil and similar supplements are derived from fat and do not contain any sugar. Some flavored oils might contain sugar, but this would be clearly indicated on the nutrition label.

It's important because while the omega-3 fat is carb-free, the food it comes in may not be. For example, a seed source has carbohydrates, while a fish source does not. Understanding this distinction is key for effectively managing carbohydrate intake for specific dietary goals.