Cod Liver Oil vs Fish Oil: What's the Difference?

Cod Liver Oil vs Fish Oil: What's the Difference?

Cod liver oil and fish oil are both marine supplements that can provide the omega-3 fatty acids EPA and DHA, but they are not interchangeable.

Ordinary fish oil is usually selected mainly for EPA and DHA. Cod liver oil also contains vitamin A and vitamin D, sometimes in substantial amounts. That difference can be useful in selected situations, but it also creates a greater risk of excessive vitamin intake, especially when cod liver oil is combined with multivitamins, vitamin D products, or prenatal supplements.

This guide compares cod liver oil vs fish oil for omega-3 content, vitamins A and D, heart and bone health, eye and immune function, pregnancy, children, side effects, interactions, dosage, and product selection.

Quick Answer: Choose fish oil when the main goal is obtaining EPA and DHA without adding substantial vitamins A and D. Cod liver oil provides omega-3 plus vitamins A and D, but the amounts vary by product and can overlap with other supplements. During pregnancy, cod liver oil and other supplements containing preformed vitamin A should generally be avoided unless a qualified prenatal professional has specifically reviewed the product.

Cod Liver Oil vs Fish Oil: Quick Comparison

Feature Cod Liver Oil Fish Oil
Source Liver of cod and related fish Body tissue of oily fish
EPA and DHA Yes Yes
Vitamin A Usually present Usually little or none unless added
Vitamin D Usually present Usually little or none unless added
Main use Omega-3 plus vitamins A and D Primarily EPA and DHA
Pregnancy suitability Generally avoided because of preformed vitamin A May be used when pregnancy-appropriate and professionally reviewed
Best label values to compare EPA, DHA, vitamin A, and vitamin D EPA and DHA

What Is Cod Liver Oil?

Cod liver oil is extracted from the liver of cod and related fish.

It naturally provides:

  • EPA
  • DHA
  • Vitamin A
  • Vitamin D

The exact amounts vary widely by brand, processing method, serving size, and whether vitamins have been removed or added back during manufacturing.

What Is Fish Oil?

Fish oil is generally extracted from the tissues of oily fish such as anchovies, sardines, mackerel, herring, salmon, or tuna.

Its main nutritional focus is:

  • EPA
  • DHA
  • Other fatty acids

Most ordinary fish-oil products do not naturally provide meaningful vitamin A or vitamin D unless these nutrients are specifically added.

Key Difference: Vitamins A and D

The biggest practical difference is that cod liver oil is both an omega-3 supplement and a vitamin A and D supplement.

This means a user must account for:

  • Vitamin A from cod liver oil
  • Vitamin D from cod liver oil
  • Vitamin A and D in a multivitamin
  • Separate vitamin D supplements
  • Fortified foods
  • Dietary liver or liver products
Label Warning: Never choose cod liver oil based only on its EPA and DHA. Check vitamin A and vitamin D per serving and calculate the total from every product you use.

EPA and DHA Comparison

Both products can provide EPA and DHA, but concentrated fish oil often provides more EPA and DHA per serving.

Cod liver oil may provide lower omega-3 amounts because part of the product's nutritional role is delivering vitamins A and D.

Label Item Cod Liver Oil Fish Oil
Total oil Does not equal total omega-3 Does not equal total omega-3
EPA Check milligrams per serving Check milligrams per serving
DHA Check milligrams per serving Check milligrams per serving
Vitamin A Important safety value Usually absent unless added
Vitamin D Important safety value Usually absent unless added

Vitamin A in Cod Liver Oil

Vitamin A is a fat-soluble vitamin involved in vision, immune function, reproduction, and normal cell growth.

Cod liver oil may contain preformed vitamin A, often labelled as:

  • Retinol
  • Retinyl palmitate
  • Retinyl acetate

Because preformed vitamin A is stored in the body, excessive long-term intake can cause toxicity.

Vitamin A Toxicity

Possible effects of excessive preformed vitamin A include:

  • Nausea
  • Headache
  • Dizziness
  • Dry or peeling skin
  • Hair loss
  • Bone or joint pain
  • Liver injury
  • Reduced bone strength
  • Birth defects during pregnancy
Pregnancy Warning: NHS guidance advises pregnant people not to take cod liver oil or supplements containing vitamin A, sometimes called retinol, because excessive vitamin A can harm fetal development.

Vitamin D in Cod Liver Oil

Vitamin D supports calcium absorption, bone health, muscle function, and normal immune activity.

Cod liver oil can contribute to vitamin D intake, but amounts vary substantially. It should not be assumed that every product provides the same dose.

Combining cod liver oil with:

  • A multivitamin
  • A prenatal vitamin
  • A standalone vitamin D product
  • Calcium plus vitamin D
  • Fortified foods

can lead to unintended duplicate intake.

Which Is Better for Heart Health?

The cardiovascular effects of both products come mainly from EPA and DHA.

Fish oil has the stronger clinical evidence base because it is available in standardized high-EPA and high-DHA formulations and in prescription products used for elevated triglycerides.

Cod liver oil is not automatically better for the heart because it contains vitamins A and D.

Evidence Perspective: NIH lists fish oil, krill oil, cod liver oil, and algal oil as omega-3 supplement sources. Clinical effects depend on the actual EPA and DHA dose rather than the product name alone.

Which Is Better for Triglycerides?

Prescription omega-3 products have the strongest established role for treating high triglycerides.

Cod liver oil is generally not an appropriate substitute because:

  • EPA and DHA may be too low
  • Vitamin A intake may become excessive
  • Vitamin D intake may become excessive
  • Prescription products are standardized and medically monitored
Medical Treatment Warning: Do not use cod liver oil to copy a high-dose prescription omega-3 regimen.

Which Is Better for Bone Health?

Cod liver oil provides vitamin D, which contributes to calcium absorption and normal bone mineralization.

However, more is not always better. Excess preformed vitamin A has been associated with concerns about bone health, particularly when intake remains high over time.

Bone health also depends on:

  • Calcium
  • Protein
  • Resistance and weight-bearing activity
  • Hormonal health
  • Fall prevention
  • Appropriate osteoporosis treatment

Which Is Better for Immune Function?

Cod liver oil supplies vitamins A and D, both of which have recognized roles in normal immune function.

This does not mean cod liver oil prevents infections or is superior to meeting nutrient needs through a balanced diet and appropriate supplementation.

Excessive vitamin A or D can cause harm.

Which Is Better for Eye Health?

Vitamin A supports normal vision, while DHA is a structural component of the retina.

Cod liver oil therefore contains nutrients relevant to eye health, but taking extra amounts does not automatically improve eyesight or treat eye disease.

Sudden vision changes, flashes, eye pain, or loss of vision require professional eye care.

Cod Liver Oil During Pregnancy

Cod liver oil is generally not recommended during pregnancy because it may contain preformed vitamin A.

NHS guidance specifically advises pregnant people not to take cod liver oil or supplements containing vitamin A.

Pregnancy omega-3 options may include:

  • Lower-mercury fatty fish
  • Pregnancy-appropriate fish oil
  • Algal DHA
  • A prenatal product containing a reviewed DHA amount
Do Not Substitute: A prenatal DHA or fish-oil supplement is not the same as cod liver oil. Always check vitamin A.

Fish Oil During Pregnancy

Fish oil may be appropriate when seafood intake is low, but product selection matters.

Check:

  • DHA per serving
  • EPA per serving
  • Purity testing
  • Fish source
  • Added vitamin A
  • Added vitamin D
  • Medication and allergy history

Read: Omega-3 During Pregnancy.

Can Children Take Cod Liver Oil?

Children should not receive adult cod liver oil without pediatric guidance.

The product may provide:

  • Too much vitamin A
  • Too much vitamin D
  • An inappropriate EPA and DHA amount
  • A choking risk if large capsules are used

Use only an age-appropriate product and dose recommended by a qualified professional.

Cod Liver Oil vs Fish Oil Side Effects

Both products may cause:

  • Fishy aftertaste
  • Burping
  • Heartburn
  • Nausea
  • Loose stools
  • Abdominal discomfort

Cod liver oil carries additional risk from excessive vitamins A and D.

Bleeding and Medication Interactions

EPA and DHA can influence platelet function.

Higher-dose use may require caution with:

  • Warfarin
  • Apixaban
  • Rivaroxaban
  • Dabigatran
  • Clopidogrel
  • Daily aspirin
  • Other anticoagulant or antiplatelet medicines
Medication Tip: Do not stop a prescribed blood thinner or aspirin in order to take cod liver oil or fish oil. Ask a pharmacist or prescriber to review the exact product.

Vitamin A Medication Concerns

Extra caution is needed with medicines related to vitamin A, including certain retinoids used for acne, psoriasis, or other conditions.

Examples may include:

  • Isotretinoin
  • Acitretin
  • Other systemic retinoids

Combining these with vitamin A-containing supplements may increase toxicity risk.

Vitamin D Medication and Health Considerations

People with kidney disease, high blood calcium, kidney stones, or conditions that alter vitamin D metabolism should not assume cod liver oil is harmless.

Added vitamin D can matter when combined with:

  • Standalone vitamin D
  • Calcium supplements
  • Thiazide diuretics
  • Other vitamin D-containing products

Fish and Seafood Allergy

People with fish allergy should not assume purified fish oil or cod liver oil is safe.

Algal oil may be a more suitable alternative, but ingredient and manufacturing warnings should still be reviewed.

Allergy Warning: Hives, facial swelling, wheezing, throat tightness, or breathing difficulty after taking a supplement requires emergency medical care.

Rancidity and Product Freshness

Both oils contain polyunsaturated fats that can oxidize.

Avoid products with:

  • A strong rancid or paint-like smell
  • A severely bitter or unusual taste
  • Leaking capsules
  • Damaged packaging
  • An expired date

Follow the manufacturer's storage instructions, especially for liquid oils.

How to Compare Labels

Label Item Cod Liver Oil Fish Oil
EPA Check milligrams Check milligrams
DHA Check milligrams Check milligrams
Vitamin A Essential safety check Usually absent unless added
Vitamin D Essential safety check Usually absent unless added
Serving size Capsules or teaspoons Capsules or teaspoons
Quality testing Purity, oxidation, contaminants Purity, oxidation, contaminants

Which One Should You Choose?

Your Goal Possible Better Fit Reason
EPA and DHA without extra vitamins Fish oil Easier to control omega-3 separately
Omega-3 plus reviewed vitamins A and D Cod liver oil May fit a specific plan if totals are calculated
Pregnancy Pregnancy-appropriate fish oil or algal DHA Cod liver oil may contain unsafe preformed vitamin A
High triglyceride treatment Prescription omega-3 Standardized medical therapy
Vegan diet Algal oil Neither cod liver oil nor fish oil is vegan
Already taking vitamin A and D Fish oil may be easier to manage Reduces duplicate vitamin exposure

How Much Should You Take?

There is no universal dose for cod liver oil or fish oil.

The right serving depends on:

  • EPA and DHA content
  • Vitamin A content
  • Vitamin D content
  • Dietary fish intake
  • Other supplements
  • Age
  • Pregnancy
  • Medication
  • Medical conditions

Read: Omega-3 Dosage.

Best Time to Take Cod Liver Oil or Fish Oil

There is no universally superior time of day.

Take either product with a meal to reduce:

  • Fishy burps
  • Nausea
  • Heartburn
  • Abdominal discomfort

Read: Best Time to Take Fish Oil.

Buying Checklist

  1. Identify the main goal.
  2. Check EPA and DHA per serving.
  3. Check vitamin A and its form.
  4. Check vitamin D.
  5. Add amounts from every other supplement.
  6. Review pregnancy, age, allergy, and medication.
  7. Look for purity and oxidation testing.
  8. Check the serving size and storage instructions.
  9. Avoid disease-cure claims.
  10. Use prescription omega-3 for medical treatment only when prescribed.

Common Myths

Myth: Cod Liver Oil Is Just Stronger Fish Oil

It is a different product because it also provides vitamins A and D.

Myth: More Vitamin A Is Always Better for Eyes

Excess preformed vitamin A can cause toxicity.

Myth: Cod Liver Oil Is Ideal During Pregnancy

It is generally avoided because of its vitamin A content.

Myth: Fish Oil Naturally Provides High Vitamin D

Most ordinary fish-oil products provide little or no vitamin D unless it is added.

Myth: Cod Liver Oil Can Replace Prescription Omega-3

It is not a standardized treatment for very high triglycerides.

Who Should Ask a Healthcare Professional First?

  • Pregnant or breastfeeding individuals
  • Children
  • People taking retinoid medicines
  • People using vitamin A or vitamin D supplements
  • People taking blood thinners or antiplatelet medicines
  • People with kidney disease, high calcium, or kidney stones
  • People with liver disease
  • People with fish allergy
  • People preparing for surgery
  • People using omega-3 for high triglycerides

Related Omega-3 Guides

Bottom Line: Fish oil is usually the simpler choice when the goal is EPA and DHA. Cod liver oil adds vitamins A and D, which may be useful only when they fit a carefully reviewed nutrition plan. During pregnancy, avoid cod liver oil unless a qualified prenatal professional has specifically approved the product.

Final Thoughts

Cod liver oil and fish oil both provide EPA and DHA, but cod liver oil also contains vitamins A and D.

That difference means cod liver oil is not automatically better. It can create duplicate intake and a greater risk of vitamin A or vitamin D excess.

Choose fish oil when you want to control EPA and DHA separately. Consider cod liver oil only when its vitamin content has been reviewed alongside diet, other supplements, medication, and medical conditions. Pregnant people should generally avoid cod liver oil because of preformed vitamin A.

Frequently Asked Questions

What is the main difference between cod liver oil and fish oil?

Both provide EPA and DHA, but cod liver oil also contains vitamin A and vitamin D.

Which has more omega-3?

Concentrated fish oil often provides more EPA and DHA per serving, but labels vary.

Is cod liver oil better than fish oil?

Not universally. It may fit a specific plan when vitamins A and D are also needed, but it creates more risk of duplicate intake.

Is cod liver oil safe during pregnancy?

It is generally avoided because it may contain preformed vitamin A, which can harm fetal development in excess.

Does fish oil contain vitamin A?

Ordinary fish oil usually contains little or no vitamin A unless it has been added.

Does fish oil contain vitamin D?

Most ordinary fish-oil products provide little or no vitamin D unless it is added.

Can cod liver oil cause vitamin A toxicity?

Yes. Excessive long-term intake can cause symptoms and may damage the liver, bones, and other tissues.

Can cod liver oil replace a vitamin D supplement?

Not automatically. The amount varies, and vitamin A exposure must also be considered.

Which is better for high triglycerides?

Prescription omega-3 products have the strongest established role. Cod liver oil should not be used as a substitute.

Can children take cod liver oil?

Only with an age-appropriate product and professional guidance because vitamins A and D can be excessive.

Can cod liver oil interact with acne medicine?

Yes. Vitamin A-containing products may interact with retinoid medicines such as isotretinoin and increase toxicity risk.

Can fish oil or cod liver oil increase bleeding?

Higher EPA and DHA doses may require caution with blood-thinning medicines and bleeding disorders.

Which is better for vegans?

Neither. Algal oil is the usual vegan source of DHA and sometimes EPA.

How should I compare products?

Compare EPA, DHA, vitamin A, vitamin D, serving size, purity testing, oxidation testing, and all other supplements you take.

About the Author

Rachel Morgan is a nutrition and wellness writer specializing in omega-3 fatty acids, vitamins A and D, supplement comparisons, pregnancy safety, and evidence-informed nutrition education.

Content reviewed and published by GetMySupplement Editorial Team. Last updated August 2, 2026.

Medical Disclaimer:

This article is for educational purposes only and should not be considered medical advice. Consult a qualified healthcare professional before using cod liver oil or high-dose fish oil, especially if you are pregnant or breastfeeding, take retinoid medicines, blood thinners, vitamin A or vitamin D supplements, have kidney or liver disease, high calcium, fish allergy, are preparing for surgery, or are considering supplementation for a child.

References

  1. NIH Office of Dietary Supplements: Omega-3 Fatty Acids Fact Sheet for Health Professionals
  2. NIH Office of Dietary Supplements: Vitamin A Fact Sheet for Health Professionals
  3. NIH Office of Dietary Supplements: Vitamin D Fact Sheet for Health Professionals
  4. NHS: Pregnancy Vitamins and Supplements
  5. NHS: Fish and Shellfish Nutrition
  6. MedlinePlus: Vitamin A
  7. MedlinePlus: Omega-3 Fatty Acids Drug Information
  8. U.S. FDA: Mixing Medications and Dietary Supplements

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