Which Vitamin Comes from Fish Oil?

November 13, 2025 •

4 min read

According to the National Institutes of Health, over a billion people worldwide are estimated to be vitamin D deficient or insufficient. While fish oil is celebrated for its omega-3s, some fish oils, specifically cod liver oil, are also sources of vitamins A and D. This guide explores the vitamins found in different fish oil products and their health implications.

Quick Summary

The distinction between standard fish oil and fish liver oil is clarified. While all contain omega-3s, only those from the liver, like cod liver oil, are natural sources of vitamins A and D. Potential health benefits and risks of these vitamins are discussed.

Key Points

Cod Liver Oil Contains Vitamins A and D: Fish liver oils, like cod liver oil, are natural sources of vitamins A and D, unlike standard fish oil supplements that are primarily for omega-3s.
Risk of Vitamin A Toxicity: Because vitamin A is fat-soluble and stored in the body, high intake from cod liver oil can be toxic, so proper dosage is critical.
Modern Fish Oil is Purified: Standard fish oil supplements are processed to remove contaminants and, in many cases, vitamins A and D, to provide concentrated omega-3s.
Not All Fish Oil is the Same: The source—fish flesh versus liver—determines the vitamin content, so reading labels is essential for choosing the right product.
Supplements are Different from Whole Foods: Eating oily fish provides omega-3s along with other beneficial nutrients that might be missing from supplements.
Consider Health Needs: Individuals should consider their overall health goals and dietary needs when choosing a fish oil product, consulting a doctor if necessary.

The Distinction Between Fish Oil and Fish Liver Oil

Not all fish oil is created equal, particularly concerning its vitamin content. Standard fish oil supplements are typically made from the oily flesh of fish such as salmon, mackerel, and anchovies, and are prized for their high concentrations of omega-3 fatty acids, namely EPA and DHA. Fish liver oils, most famously cod liver oil, are different. As the name suggests, they are extracted from the liver, which is where fish store their fat-soluble vitamins. Cod liver oil is a source of both vitamin A and vitamin D.

Cod Liver Oil: A Natural Source of Vitamins A and D

Historically, cod liver oil has been used to prevent vitamin deficiencies, particularly rickets. A single tablespoon of cod liver oil can contain significant amounts of vitamin A and D. Vitamin A is crucial for maintaining eyesight, skin health, and a robust immune system. Vitamin D is vital for bone health because it facilitates the absorption of calcium and phosphorus and plays a role in immune function.

Vitamin A: Supports immune function, vision, and cell growth.
Vitamin D: Aids in calcium absorption and bone health, and supports immune function.
Omega-3 Fatty Acids (EPA and DHA): Reduces inflammation and supports heart and brain health.

The Health Implications of Excess Vitamins

While vitamins A and D are essential, they are fat-soluble. Excessive intake, especially of vitamin A, can lead to hypervitaminosis A, which can be toxic. This is a particular concern with fish liver oil supplements, where a small dose can deliver a large amount of vitamin A. Modern, purified fish oil supplements often remove these vitamins, making them a safer choice for those seeking only omega-3 benefits. The National Center for Complementary and Integrative Health (NCCIH) advises that while fish liver oil supplements contain vitamins A and D, these fat-soluble vitamins can be harmful in excessive amounts.

Fish Oil vs. Cod Liver Oil: A Comparison

To highlight the differences:


Feature	Standard Purified Fish Oil	Cod Liver Oil
Source	Oily fish flesh (e.g., salmon, anchovy, mackerel)	Cod liver
Primary Purpose	Omega-3 supplementation (EPA & DHA)	Omega-3, plus vitamins A & D
Vitamin Content	Insignificant amounts of vitamins A & D, often removed during processing	High in naturally occurring vitamins A & D
Risks of High Dose	Risk of bleeding or interaction with blood thinners at high doses.	Risk of vitamin A toxicity (hypervitaminosis A).
Best for	Individuals seeking concentrated omega-3s without extra vitamins.	Those addressing a specific deficiency in vitamins A or D, or seeking a natural source.

How to Safely Choose a Fish Oil Supplement

For consumers, navigating the fish oil supplement market requires careful label reading. If your goal is to boost your omega-3 intake without concern for added vitamins, a standard, purified fish oil is the correct choice. However, if you are looking for a natural source of vitamins A and D alongside omega-3s, cod liver oil is an option, but caution is necessary. It is essential to follow dosage instructions carefully to avoid toxicity. Pregnant women and individuals taking blood-thinning medication should consult a healthcare provider before taking cod liver oil.

Conclusion

In summary, the answer to "which vitamin comes from fish oil?" depends on the type of fish oil. Standard fish oil is predominantly a source of omega-3 fatty acids. Fish liver oil, such as cod liver oil, is a significant natural source of vitamins A and D, along with omega-3s. Understanding this difference is crucial for making informed decisions about supplementation. Always read the product label and consider consulting a healthcare professional.

The Importance of Natural Omega-3s

For those who prefer whole food sources, eating fatty fish such as salmon, mackerel, and herring is the best way to get a balanced intake of omega-3s. This approach also provides other beneficial nutrients. The American Heart Association recommends eating two servings of fatty fish per week.

A Final Word on Supplementation

Whether you opt for cod liver oil or a purified fish oil supplement, responsible supplementation is key. Choose high-quality products from reputable brands. Being aware of the vitamin content is important for a healthier supplementation routine.

Omega-3s are the primary active ingredient in fish oil supplements.

Fish liver oils, like cod liver oil, contain naturally occurring vitamins A and D.

High doses of cod liver oil can lead to vitamin A toxicity.

The refining process for most modern fish oil supplements removes vitamins A and D.

Always check the product label to see if it's pure fish oil or fish liver oil.

For omega-3 benefits without extra vitamins, choose standard purified fish oil.

For a natural source of vitamins A and D, along with omega-3s, consider cod liver oil.

Frequently Asked Questions

The main difference is the source: regular fish oil is made from the oily flesh of fish and is valued for its omega-3s, while cod liver oil is extracted specifically from the liver of cod and naturally contains vitamins A and D in addition to omega-3s.

No, fish oil is not the same as a multivitamin. Standard fish oil is primarily a source of omega-3 fatty acids, whereas multivitamins contain a range of different vitamins and minerals. While cod liver oil contains vitamins A and D, it does not provide the full spectrum of vitamins found in a multivitamin.

Yes, if you are consuming fish liver oils like cod liver oil, it is possible to get too much vitamin A. High doses can be toxic, so it is important to stick to the recommended dosage and consult a healthcare provider, especially if you take other supplements with vitamin A.

Vitamin D is naturally present in fish liver oils, but not in significant amounts in standard fish oil supplements, which are purified from the oily flesh of the fish. If you want vitamin D from a fish oil supplement, you should specifically look for cod liver oil or a similar fish liver oil product.

People taking blood thinners like Warfarin should avoid cod liver oil due to its potential to increase bleeding risk. Pregnant and breastfeeding women, and those on other vitamin A supplements, should also be cautious due to the risk of vitamin A toxicity.

The product label is the best source of information. It should specify if the oil is 'cod liver oil' or derived from fish liver, and the nutritional information panel will list the amounts of vitamins A and D per serving. If it is a purified fish oil supplement, it will typically not contain these vitamins.

For most people, getting omega-3s by eating whole fish is preferable as it also provides other important nutrients. However, supplements are a viable alternative for those who don't eat fish regularly or have concerns about contaminants like mercury, which is often removed during the refinement process.