Evidence-based·Last reviewed May 31, 2026·How we grade evidence

Fish Liver oil

Q: Should I take cod liver oil in pregnancy?

Avoid high-vitamin-A formulations. Prenatal-friendly EPA/DHA+vitamin D products are safer.

Q: Is cod liver oil better than fish oil?

It adds vitamins A and D but limits how much EPA/DHA you can safely take. For high EPA/DHA dosing, use standard fish oil.

Fatty-acidOmega-3Best with a meal

Fish liver oil — most commonly cod liver oil — is the original 'one supplement, three actives' product: vitamin A (retinol), vitamin D, and omega-3 fatty acids (EPA/DHA). It's a sensible vitamin D + omega-3 source in winter for people who don't eat oily fish. The catch: one teaspoon of high-potency cod liver oil can put a pregnant woman over the vitamin-A pregnancy UL of 3,000 µg/day, with documented teratogenic risk. This is not 'fish oil' — that's a refined body-oil product with no vitamin A.

Quick decision guide

May help most

Adults who don't eat oily fish, live at high latitudes, and want a single product delivering moderate vitamin D and EPA+DHA. Traditional use in northern Europe to cover vitamin D and A through winter has real (if old) clinical roots.

Common dosing range

1 teaspoon (~4.5 g) per day is the traditional dose. Check YOUR bottle: typical content is ~890 µg retinol (~2,964 IU vitamin A), ~450 IU vitamin D, ~890 mg combined EPA+DHA per teaspoon — but products vary widely.

When to expect effects

Weeks to months for nutrient status (vitamin D, omega-3 index). Cardiovascular biomarker effects from omega-3 take 3–6 months.

Watch out for

Pregnancy: vitamin A teratogenicity above 3,000 µg/day. One tablespoon of high-potency cod liver oil can exceed this. Use a vitamin-A-removed prenatal omega-3 product instead, or restrict to teaspoon doses with your obstetric provider's input.

Evidence snapshot

Vitamin D status (winter / low-sunlight)Moderate

Vitamin A status (Western diets without organ meat)Moderate

Omega-3 (EPA/DHA) statusModerate

Cardiovascular outcomesEmerging

Pregnancy use (vitamin A risk)Caution

What is it

Fish liver oil (most commonly cod liver oil) is oil extracted from the livers of fatty fish. Unlike standard fish oil, it provides not just EPA and DHA but also significant amounts of vitamin A and vitamin D.

Is it worth it for you?

Use this as a quick fit check, not a diagnosis.

Worth considering if…

You don't eat oily fish and want a single product covering vitamin D, vitamin A, and EPA+DHA

You live at high latitudes or get very little sunlight in winter

You prefer a traditional whole-food-style omega-3 source over a refined fish-oil capsule

You can stick to roughly 1 teaspoon/day and aren't stacking with a high-vitamin-A multivitamin or retinoid acne medication

Probably skip if…

You're pregnant, planning pregnancy, or could become pregnant — vitamin A teratogenicity above 3,000 µg/day is real (use a vitamin-A-free prenatal omega-3 instead)

You're already taking isotretinoin, acitretin, or a high-vitamin-A multivitamin — additive toxicity

You only want omega-3 — refined fish oil (no vitamin A) is cleaner for high-dose use

You have liver disease — preformed vitamin A is hepatotoxic at chronic high intake

You take warfarin and aren't coordinating with your prescriber — omega-3 mildly potentiates bleeding risk

Evidence at a glance

Goal	Effect	Best fit	Time
Vitamin D status (winter / low-sunlight) Good Evidence	Reliable rise in serum 25(OH)D over weeks to months at 1 tsp/day in vitamin-D-insufficient adults	Adults at high latitudes, indoor workers, people with darker skin, older adults, breastfed infants (use a vitamin-D-only product designed for infants — not adult cod liver oil)	8–12 weeks for serum 25(OH)D rise
Omega-3 (EPA + DHA) status and cardiovascular biomarkers Good Evidence	Reliable rise in omega-3 index; modest TG reduction (~10–15%) at ≥1 g EPA+DHA/day	Adults not eating ≥2 servings of oily fish per week	8–12 weeks for omega-3 index; 3–6 months for triglyceride effect
Vitamin A status (Western diets) Limited Evidence	Substantial single-source vitamin A contribution; can exceed RDA at 1 tsp/day	Adults with fat-malabsorption disorders or low organ-meat / dairy / orange-vegetable intake	Weeks for serum retinol if deficient
General cardiovascular health Limited Evidence	Modest triglyceride and omega-3-index improvements; no hard-endpoint evidence specifically for cod liver oil	Adults using cod liver oil as part of a heart-healthy diet alongside lifestyle measures	3–6 months

Vitamin D status (winter / low-sunlight)

Good Evidence

Effect: Reliable rise in serum 25(OH)D over weeks to months at 1 tsp/day in vitamin-D-insufficient adults
Best fit: Adults at high latitudes, indoor workers, people with darker skin, older adults, breastfed infants (use a vitamin-D-only product designed for infants — not adult cod liver oil)
Time: 8–12 weeks for serum 25(OH)D rise

Omega-3 (EPA + DHA) status and cardiovascular biomarkers

Good Evidence

Effect: Reliable rise in omega-3 index; modest TG reduction (~10–15%) at ≥1 g EPA+DHA/day
Best fit: Adults not eating ≥2 servings of oily fish per week
Time: 8–12 weeks for omega-3 index; 3–6 months for triglyceride effect

Vitamin A status (Western diets)

Limited Evidence

Effect: Substantial single-source vitamin A contribution; can exceed RDA at 1 tsp/day
Best fit: Adults with fat-malabsorption disorders or low organ-meat / dairy / orange-vegetable intake
Time: Weeks for serum retinol if deficient

General cardiovascular health

Limited Evidence

Effect: Modest triglyceride and omega-3-index improvements; no hard-endpoint evidence specifically for cod liver oil
Best fit: Adults using cod liver oil as part of a heart-healthy diet alongside lifestyle measures
Time: 3–6 months

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Vitamin D status (winter / low-sunlight)

Corrects deficiency

Good Evidence

One teaspoon of cod liver oil supplies roughly 400–1,360 IU vitamin D, depending on the product. This is in the same ballpark as a standalone vitamin D3 supplement at 500–1,000 IU/day and consistently raises serum 25(OH)D in people with low intake. Historically (early 20th century) cod liver oil was the standard cure for rickets — a testimony to its vitamin D content.

Effect size

Reliable rise in serum 25(OH)D over weeks to months at 1 tsp/day in vitamin-D-insufficient adults

Time to effect

8–12 weeks for serum 25(OH)D rise

Best fit

Adults at high latitudes, indoor workers, people with darker skin, older adults, breastfed infants (use a vitamin-D-only product designed for infants — not adult cod liver oil)

Less likely

Adults with adequate sun exposure and a varied diet already including oily fish

Bottom line: Solid vitamin D source; check YOUR bottle for IU content per teaspoon, since it varies widely between brands.

SourceNIH ODS Vitamin D Health Professional Fact Sheet — NIH Office of Dietary Supplements

Omega-3 (EPA + DHA) status and cardiovascular biomarkers

Biomarker support

Good Evidence

Cod liver oil supplies approximately 500–1,000 mg combined EPA+DHA per teaspoon — meeting or exceeding the American Heart Association's general-health target of 250–500 mg combined EPA+DHA per day. EPA and DHA reliably raise the omega-3 index and modestly lower triglycerides (~10–15% at 1 g+ EPA+DHA/day). Hard cardiovascular endpoint trials of fish oil have been mixed (REDUCE-IT positive, STRENGTH negative); none of those trials specifically used cod liver oil. See /nutrients/omega-3 for the full evidence review.

Effect size

Reliable rise in omega-3 index; modest TG reduction (~10–15%) at ≥1 g EPA+DHA/day

Time to effect

8–12 weeks for omega-3 index; 3–6 months for triglyceride effect

Best fit

Adults not eating ≥2 servings of oily fish per week

Less likely

Adults already eating oily fish 2–3×/week (you'll exceed a moderate EPA+DHA intake without supplementing)

Bottom line: Reasonable omega-3 source. For high-dose EPA-only (cardiovascular) use, switch to refined fish oil — cod liver oil's vitamin A content makes high-dose use risky.

SourceNIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements

Vitamin A status (Western diets)

Corrects deficiency

Limited Evidence

Cod liver oil is a meaningful preformed-vitamin-A source — roughly 890 µg retinol per teaspoon (~3,000 IU). Frank vitamin A deficiency is rare in developed countries; deficiency is more common in low-income settings and in fat-malabsorption disorders (cystic fibrosis, advanced liver disease, post-bariatric surgery). For those populations, cod liver oil is a logical source. For everyone else, it's at most a modest contribution to the RDA (900 µg/day men, 700 µg/day women).

Effect size

Substantial single-source vitamin A contribution; can exceed RDA at 1 tsp/day

Time to effect

Weeks for serum retinol if deficient

Best fit

Adults with fat-malabsorption disorders or low organ-meat / dairy / orange-vegetable intake

Less likely

Healthy adults with varied diets — most already exceed the RDA without supplementing

Bottom line: Real vitamin A source — useful in deficiency, but a teratogenic risk in pregnancy if intake stacks. Track total preformed vitamin A across diet + all supplements.

SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements

General cardiovascular health

Supplement benefit

Limited Evidence

Modest reductions in triglycerides, slight BP-lowering, and improved omega-3 index are consistently shown with EPA+DHA in the 1–2 g/day range. Hard endpoint trials (REDUCE-IT, STRENGTH) used pharmaceutical-grade EPA at much higher doses (~4 g/day) and showed mixed results. Cod liver oil at 1 tsp/day is best viewed as a sensible dietary backbone, not a cardiovascular treatment.

Effect size

Modest triglyceride and omega-3-index improvements; no hard-endpoint evidence specifically for cod liver oil

Time to effect

3–6 months

Best fit

Adults using cod liver oil as part of a heart-healthy diet alongside lifestyle measures

Less likely

Adults with established cardiovascular disease seeking pharmacologic-dose EPA — pick prescription icosapent ethyl (or high-dose refined EPA) instead

Bottom line: Don't take cod liver oil for primary cardiovascular treatment. For that, talk to your cardiologist about prescription EPA.

SourceNIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements

How it works

EPA and DHA function as omega-3 fatty acids (membrane phospholipid composition, anti-inflammatory eicosanoid precursors, triglyceride lowering at higher doses). Vitamin A supports vision, epithelial integrity, and immune function. Vitamin D supports calcium absorption and immune modulation. Because vitamin A is concentrated in fish liver, fish liver oil dose is limited by vitamin A toxicity risk rather than EPA/DHA content.

How to take it

1. Typical dose

• Standard adult dose: 1 teaspoon (~4.5 g) per day • Approximate per-teaspoon content (varies): ~890 µg retinol, ~450 IU vitamin D, ~890 mg EPA+DHA — CHECK YOUR BOTTLE • Don't exceed 1 tablespoon (3 tsp) per day in any adult — vitamin A approaches the 3,000 µg/day UL

2. Higher studied dose

Historical northern European doses ran 1 tablespoon/day in winter — that brings preformed vitamin A close to the 3,000 µg adult UL and is not recommended chronically. For higher-dose omega-3 use, switch to refined fish oil (no vitamin A) to avoid retinol toxicity.

3. Timing

With a meal containing fat — vitamins A and D and the long-chain omega-3s all absorb best with dietary fat.

4. With food

With a fat-containing meal.

5. Split dosing

No benefit at 1 tsp/day. Could split if going to 2 tsp.

6. How long to try

Indefinite as a dietary supplement, with periodic re-check of vitamin D and (if relevant) vitamin A status. Reassess if you start a retinoid medication or change your diet.

What to track

Serum 25(OH)D every 6–12 months to confirm vitamin D adequacy

If on cod liver oil long-term or stacking with a multivitamin: check that total preformed vitamin A from all sources stays well under 3,000 µg/day

Triglycerides at 3–6 months if cardiovascular biomarkers are the goal

Any signs of vitamin A toxicity at chronic high intake: dry skin, hair loss, headache, joint pain, hepatic enzyme rise

Bottom line: 1 tsp/day with food is the right default. The vitamin A ceiling is the binding constraint, not the omega-3 dose — if you want more omega-3, use refined fish oil on top.

5 commercial forms

Compare the main delivery options and what they’re best suited for.

Cod liver oil (liquid)

Classic

Traditional Norwegian / Icelandic form. Easiest to dose precisely by teaspoon. Most products today are deodorized and may include lemon or other flavors. Look for third-party testing for mercury and PCBs.

Standard; absorbed with dietary fat.

Cod liver oil softgels

Convenient

Capsules typically deliver 1,000 mg of cod liver oil per softgel — you may need 4–5 softgels to equal 1 tsp. Convenient for travel; less precise dosing if you want to titrate.

Equivalent to liquid form per gram of oil.

Fermented cod liver oil

Caveat

Marketed by certain niche brands as more 'natural.' Independent testing has repeatedly found inconsistent vitamin A and D content vs label, and signs of oxidation. Prefer molecularly distilled, third-party-tested standard products.

Variable; product-quality concerns repeatedly raised.

Halibut liver oil / shark liver oil

Higher vitamin A

Even higher vitamin A content per teaspoon than cod liver oil — often >7,500 µg RAE per teaspoon. Easy to exceed UL with daily use; reserve for short-term medical supplementation, not casual long-term use.

Similar to cod liver oil per gram; vitamin A density is the practical issue.

Refined fish oil (no vitamin A) — separate product

Alternative for omega-3

Standard fish body oil (anchovy, sardine, mackerel) is refined to deliver EPA+DHA without significant vitamin A or D. Use this instead when you want gram-doses of omega-3 without retinol toxicity risk. See /nutrients/omega-3.

Standard omega-3 bioavailability; no vitamin A or D unless added back.

Safety

Know the common side effects, key cautions, and who should avoid it.

Common side effects

fishy aftertasteburpingmild GI upsetloose stools at higher doses

Serious risks

Preformed vitamin A teratogenicity in pregnancy — intake above 3,000 µg RAE/day (~10,000 IU/day) is associated with cranial-neural-crest birth defects. One tablespoon (3 tsp) of high-potency cod liver oil can put a pregnant woman over this threshold.
SourceRothman et al., 1995 (NEJM) — PubMed — New England Journal of Medicine NIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
Chronic vitamin A toxicity (hypervitaminosis A) at sustained intake above the 3,000 µg/day UL — symptoms include hair loss, dry/peeling skin, headache, joint pain, hepatic enzyme elevation, and in severe cases liver failure.
SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
Bleeding risk from EPA+DHA at high cumulative doses — typically only clinically meaningful at ≥3 g EPA+DHA/day or in combination with warfarin/antiplatelet drugs; not usually an issue at 1 tsp/day.
SourceNIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements
Vitamin D toxicity at sustained intake well above 10,000 IU/day — not a typical risk at 1 tsp/day cod liver oil, but can occur when stacked with high-dose vitamin D supplements.
SourceNIH ODS Vitamin D Health Professional Fact Sheet — NIH Office of Dietary Supplements

Who should avoid it

Pregnant women and women planning pregnancy — use a vitamin-A-free prenatal omega-3 product instead, or restrict to a teaspoon dose with your obstetrician's input.
SourceRothman et al., 1995 (NEJM) — PubMed — New England Journal of Medicine NIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
People taking isotretinoin (Accutane), acitretin, bexarotene, or other systemic retinoids — additive vitamin A toxicity.
SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
People taking a high-vitamin-A multivitamin or organ-meat-heavy diets without tracking total preformed vitamin A intake.
SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
People with chronic liver disease — preformed vitamin A is hepatotoxic at sustained high intake.
SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements
People on warfarin or aggressive antiplatelet therapy without prescriber coordination — modest additive bleeding risk from EPA/DHA.
SourceNIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements

Pregnancy & breastfeeding

Use with caution. Preformed vitamin A above 3,000 µg/day (~10,000 IU/day) in early pregnancy is teratogenic (Rothman 1995, NEJM). One tablespoon of high-potency cod liver oil can exceed this. Safer options for pregnant women who want omega-3: a vitamin-A-free prenatal omega-3 (DHA-focused) product, or restrict cod liver oil to a single teaspoon AFTER confirming the vitamin A content per teaspoon with your obstetric provider. Vitamin D and DHA needs in pregnancy can be met without cod liver oil.

SourceRothman et al., 1995 (NEJM) — PubMed — New England Journal of Medicine NIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements

Bottom line: Vitamin A teratogenicity in pregnancy and chronic hypervitaminosis A in everyone else are the dominant safety messages. Track total preformed vitamin A across diet + all supplements.

Interactions

systemic retinoids (isotretinoin, acitretin, bexarotene)Major

Additive vitamin A toxicity. Avoid cod liver oil while on systemic retinoid therapy.

SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements

warfarin / DOACs / antiplatelet drugsModerate

EPA+DHA mildly potentiates anticoagulant effect at higher cumulative doses. Coordinate with your prescriber if you're on warfarin or are about to have surgery (some surgeons ask patients to stop fish oil 1 week pre-op).

SourceNIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements

high-vitamin-A multivitamins or fortified productsModerate

Cumulative preformed vitamin A can exceed the 3,000 µg/day UL. Read all labels and add up your total daily retinol intake.

SourceNIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements

high-dose vitamin D supplementsMinor

Possible additive vitamin D buildup at sustained intake well above 10,000 IU/day combined. Track total daily vitamin D.

SourceNIH ODS Vitamin D Health Professional Fact Sheet — NIH Office of Dietary Supplements

orlistatMinor

Fat-blocking weight-loss drug reduces absorption of fat-soluble vitamins (A, D, E, K). Separate cod liver oil from orlistat by ≥2 hours.

Food sources

Food	Amount	%DV
Cod liver oil (1 tsp / 4.5 g)	1 tsp (~890 µg RA, ~450 IU D, ~890 mg EPA+DHA)	—
Cod liver oil (1 Tbsp / 13.6 g)	1 Tbsp (~2,670 µg RA, ~1,350 IU D, ~2,670 mg EPA+DHA — approaches vitamin A UL)	—
Beef liver (cooked)	3 oz (~6,500 µg RA)	—
Salmon, wild Atlantic (cooked)	3 oz (~570 IU D, ~1,500 mg EPA+DHA, minimal vitamin A)	—
Mackerel (cooked)	3 oz (~360 IU D, ~1,000 mg EPA+DHA, minimal vitamin A)	—

Cod liver oil (1 tsp / 4.5 g)

Amount: 1 tsp (~890 µg RA, ~450 IU D, ~890 mg EPA+DHA)
%DV: —

Cod liver oil (1 Tbsp / 13.6 g)

Amount: 1 Tbsp (~2,670 µg RA, ~1,350 IU D, ~2,670 mg EPA+DHA — approaches vitamin A UL)
%DV: —

Beef liver (cooked)

Amount: 3 oz (~6,500 µg RA)
%DV: —

Salmon, wild Atlantic (cooked)

Amount: 3 oz (~570 IU D, ~1,500 mg EPA+DHA, minimal vitamin A)
%DV: —

Mackerel (cooked)

Amount: 3 oz (~360 IU D, ~1,000 mg EPA+DHA, minimal vitamin A)
%DV: —

Choosing a product

What to look for on the label — and what to be skeptical of.

Look for…

Vitamin A content per serving CLEARLY stated in µg RAE (or IU) — not just 'contains vitamin A'

Vitamin D content per serving in IU

Combined EPA+DHA content per serving in mg

Molecularly distilled or third-party tested for heavy metals (mercury) and PCBs

Cold-pressed, low-temperature processing to preserve omega-3s

Mixed tocopherols (vitamin E) added to prevent oxidation

If you're using it in pregnancy: vitamin A content low (<600 µg RAE per serving) or product explicitly designed as 'prenatal cod liver oil'

Be skeptical of…

'Safe in pregnancy' on high-potency cod liver oil — only safe if you stay well under the 3,000 µg vitamin A UL across diet + all supplements

'Better than fish oil' as a blanket claim — for high-dose omega-3 use, refined fish oil (no vitamin A) is cleaner

Combination products bundling cod liver oil with a multivitamin without disclosing total vitamin A across both

Marketed 'fermented' cod liver oil products with no third-party testing for oxidation, contaminants, or actual vitamin A and D content

'Anti-aging skin' marketing — there's no specific clinical evidence for cosmetic benefit from oral cod liver oil

Frequently asked questions

Should I take cod liver oil in pregnancy?⌄

Avoid high-vitamin-A formulations. Prenatal-friendly EPA/DHA+vitamin D products are safer.

Is cod liver oil better than fish oil?⌄

It adds vitamins A and D but limits how much EPA/DHA you can safely take. For high EPA/DHA dosing, use standard fish oil.

References by claim

Safety

Rothman et al., 1995 (NEJM) — PubMed — New England Journal of Medicine (1995) link

Vitamin A status (Western diets)

NIH ODS Vitamin A Health Professional Fact Sheet — NIH Office of Dietary Supplements (2024) link

Vitamin D status (winter / low-sunlight)

NIH ODS Vitamin D Health Professional Fact Sheet — NIH Office of Dietary Supplements (2024) link

Omega-3 (EPA + DHA) status and cardiovascular biomarkers

NIH ODS Omega-3 Fatty Acids Fact Sheet — NIH Office of Dietary Supplements (2024) link

Other references

USDA FoodData Central — Fish oil, cod liver — USDA (2024) link

Fish liver oil on Wikidata — Wikidata link

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Evidence-based·Last reviewed May 31, 2026·Evidence current as of May 31, 2026·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.